Powerboater's Guide to Electrical Systems, Second … public/Jurine praktika/Powerboater's... · Malestrom. Maintenance,Troubleshooting, and Improvements Ed Sherman Second Edition

Malestrom

Maintenance, Troubleshooting,and Improvements

Ed Sherman

Second Edition

Powerboater’sGuide to

ElectricalSystems

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DedicationTo my wife, Nancy, and son, Mason, who have to put up with

me when I’m involved in projects like this!

Copyright © 2000, 2007 by Edwin R. Sherman. Click here for terms of use.

Foreword to the Second Edition by Skip Burdon, President and CEO, American Boat & Yacht Council . . . . . . . . . . .vii

Preface to the Second Edition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .ixIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .x

Chapter 1. Electrical Basics You Need to Know . . . . . . . . . . . . . .1What Is Electricity? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Electrical Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Ohm’s Law and What It Can Tell Us . . . . . . . . . . . . . . . . . . . . . . . . . .5Voltage Drop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Putting It All Together . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Circuit Problems and How They Occur . . . . . . . . . . . . . . . . . . . . . . .9Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Chapter 2. Working with Wiring Diagrams . . . . . . . . . . . . . . . . . .12The Trouble with Boats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Common Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Component Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14Wire Identification and the ABYC Color Code . . . . . . . . . . . . . . . .15Expanding the Basic Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Locating Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20Drawing Your Own Wiring Diagram . . . . . . . . . . . . . . . . . . . . . . . .22

Chapter 3. Selecting and Using a Multimeter . . . . . . . . . . . . . . .25Multimeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Selecting a Multimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Using Your Multimeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Measuring Amperage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34Measuring Resistance and Continuity . . . . . . . . . . . . . . . . . . . . . . . .37

Chapter 4. Wire and Circuit ProtectionStandards and Repair Procedures . . . . . . . . . . . . . . . . . . . . . . . .40Order Out of Chaos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40ABYC Standards and Recommendations . . . . . . . . . . . . . . . . . . . . .40Basic Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41Wire Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42Wire Insulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43Fuses and Circuit Breakers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46Ignition Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52Testing Fuses and Circuit Breakers . . . . . . . . . . . . . . . . . . . . . . . . . .53Levels of Circuit Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54

Contents

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Acceptable Locations for Fuses and Circuit Breakers . . . . . . . . . . . .55Wire Routing and Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57Connecting the Dots: Making Wiring and Connection Repairs . . .59

Chapter 5. Batteries and Battery Systems . . . . . . . . . . . . . . . . . . .65How Batteries Work: The Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . .65Basic Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65Types of Lead-Acid Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66Which Battery Is Right for You? . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69Battery Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72Battery Maintenance and Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . .74Battery Installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76Testing Your Batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82

Chapter 6. Battery-Charging Systems . . . . . . . . . . . . . . . . . . . . . . .86Alternator Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86Engine-Driven Marine Alternators . . . . . . . . . . . . . . . . . . . . . . . . . .87Alternator Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87Outboard-Engine Charging Systems . . . . . . . . . . . . . . . . . . . . . . . . .94Shore-Power Battery Charging Systems and Installations . . . . . . . .96Solar Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99

Chapter 7. Maintaining Marine Ignition Systems . . . . . . . . . . .100Ignition-System Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100Regulations Regarding Ignition Systems . . . . . . . . . . . . . . . . . . . . .103Outboard and PWC Ignition Systems . . . . . . . . . . . . . . . . . . . . . . .103Maintaining Ignition Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104MerCruiser Thunderbolt IV and Thunderbolt V Systems . . . . . . .107Beyond the Basics: Outboard and PWC Ignition Systems . . . . . . .110Outboard and PWC Ignition Tests . . . . . . . . . . . . . . . . . . . . . . . . .112Testing Your Stop Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119Final Checks and Ignition Timing . . . . . . . . . . . . . . . . . . . . . . . . . .120

Chapter 8. Tracing and Repairing Starter-Motor Circuits . . . . .123Coast Guard Regulations for Starter Motors . . . . . . . . . . . . . . . . . .123Starter-Motor Problems and Solutions . . . . . . . . . . . . . . . . . . . . . .124Troubleshooting Starter-Motor Circuits . . . . . . . . . . . . . . . . . . . . .125Outboard-Engine Starter Circuits . . . . . . . . . . . . . . . . . . . . . . . . . .128Testing the Neutral-Safety Switch . . . . . . . . . . . . . . . . . . . . . . . . . .132Engine Ignition Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133Other Outboard-Engine Starter-Motor Problems . . . . . . . . . . . . .135

Chapter 9. Installing Your Own DC Accessories . . . . . . . . . . . . .136Before You Begin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .136Installing a New Cabin Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139Installing a New Bilge Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140Adding a New Compact-Disc Player . . . . . . . . . . . . . . . . . . . . . . . .144

Alt

C O N T E N T S

Chapter 10. Engine Instrumentation Problems and Solutions .147Mechanical Gauges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147Common Instrument Interpretation Problems . . . . . . . . . . . . . . .147Abnormal Instrument Readings . . . . . . . . . . . . . . . . . . . . . . . . . . . .148General Instrument Troubleshooting . . . . . . . . . . . . . . . . . . . . . . .149The Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155

Chapter 11. Alternating Current and AC Equipment . . . . . . . . . .156What Is Alternating Current? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .156AC on Your Boat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157AC Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157Color Coding for AC Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158Comparisons between AC and DC Circuits . . . . . . . . . . . . . . . . . .159AC Overcurrent Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162Basic AC Outlet Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164Ground-Fault Circuit Interrupters . . . . . . . . . . . . . . . . . . . . . . . . . .166Checking Voltage, Continuity, and Polarity on AC Circuits . . . . .167Selecting a DC-to-AC Inverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170AC Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175Galvanic Isolators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177

Chapter 12. Installing Marine Electronic Equipment . . . . . . . . .180Electronic Gadgetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .180Universal Installation Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .180Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182Installing a VHF Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183How Much Can I Gain? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184The Coaxial Question . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184Installing a Fish-Finder or Depth-Sounder . . . . . . . . . . . . . . . . . . .186Installing a GPS Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .190Installing Your Own Radar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201

C O N T E N T S

vii

It can arguably be said that harnessing the electron hasbeen one of humankind’s crowning achievements.For thousands of years, people—including those whohave sailed the seas—have been fascinated by light-ning, static electricity, and harnessing light. Early hu-mans must have wondered how to put that kind ofpower to practical use. But it wasn’t until the close of the 18th century that the path to everyday use ofelectrical power would begin to have a profound andlasting impact the world over, including at sea.

We all know about Benjamin Franklin, who in1752 proved that lightning was electrical when heflew a kite during a thunderstorm. He tied a metalkey onto the string and, as he suspected it would,electricity from the storm clouds flowed down thestring, which was wet, and he received an electricalshock. Maybe not the smartest of ideas, but it surebrought the point home fast!

Throughout the next hundred years, many in-ventors and scientists tried to find a way to use elec-trical power to make light. In 1879, Thomas Edisonwas finally able to produce a reliable, long-lastingelectric light bulb in his laboratory. From that pointforward, the world would witness profound tech-nological advances.

By the end of the 1880s, small electrical stationsbased on Edison’s designs were springing up in anumber of U.S. cities. But each station was able topower only a few city blocks. Elementary electricalsystems were beginning to find their way onto ships,and onto pleasure craft reserved for the affluent few.During those early days, electrical safety standardswere virtually nonexistent, both on land and at sea.

Although the majority of people living in largertowns and cities had electricity by 1930, only 10 per-cent of Americans who lived on farms and in ruralareas had electric power. But that was about to changerapidly through the 1940s and 1950s as America wasthrust onto the world stage fighting a second worldwar, the Korean conflict, and the Cold War.

Today, the standard of living across the globe hasrisen as more and more people experience the con-venience of electric power at home, school, work,and at sea. If there is any doubt in your mind, try toexist for one day without any influence of the powerof the electron. You’ll quickly discover that you willliterally be back in the Dark Ages.

In harnessing the power of the electron, it wasrecognized early on that standards were needed forreasons of both practicality and safety. For recre-ational boats and yachts, the American Boat & YachtCouncil (ABYC)—a nonprofit industry member-ship organization—has been developing, writing,and updating the safety standards for boatbuildingand repair in the United States for over 50 years.This includes electrical safety standards.

Over the past half century, the ABYC has cometo be known as the recognized global leader in ma-rine safety standards research, development, inter-national harmonization, and co-recognition. ABYCstandards are endorsed and used by the UnitedStates Coast Guard, Transport Canada, the NationalMarine Manufacturers Association (NMMA) Boatand Yacht Certification program, the internationalcommunity, and by virtually every industry seg-ment. Over 400 of our member volunteers donatetime, expertise, and research while serving on tech-nical committees that develop and revise the ABYCstandards and technical information reports.

The positive, lifesaving impact of the ABYC stan-dards cannot be overstated, but perhaps none moreso than in the area of wiring and electrical systemsinstallation, maintenance, and repair of boats andyachts. Proper electrical system design, wiring typeand size, overcurrent protection, wire termination,power source management, proper installation andintegration of electronic sensing and control com-ponents, and the networking of all critical systemshave and will significantly reduce injury and fatali-ties caused by electrical fires and shock and damage

Foreword to the Second Edition


viii

to watercraft components, accessories, and systems.Simply put, ABYC standards, and in particular,ABYC electrical standards, save lives and property!

In addition to developing and disseminating in-dustry standards, the ABYC has taken the lead in ad-vocating, providing, and promoting technicalworkforce professional development, continuingeducation, and technical workforce certifications.Three courses that make extensive use of Ed’s bookare the ABYC Basic Electricity course, the ABYCElectrical Certification course, and the ABYC Ma-rine Systems Certification courses. Additionally, hisbook is a resource for all boaters and want-to-beboaters who want to take ABYC “boater” courses,seminars, and workshops. Visit www.abyc.com tolearn more about the ABYC, its mission, and its ed-ucational offerings. And when buying a boat, ensurethat it is NMMA certified using ABYC standards!

Over the years I have come to know Ed as both aprofessional and as a friend. As a professional, he hasdesigned both the ABYC Basic Electricity course andthe ABYC Electrical Certification course. He also hasrecently completed the National Marine curriculumguidelines for secondary schools that offer ABYC-endorsed technical marine programs, and he hascodeveloped a post-secondary Marine Systems Cur-riculum that is scheduled to be implemented in anumber of schools across the country. Ed’s teachingand writing skills and his rapport with students arelegendary and beyond reproach. He is regarded as anindustry expert in the area of electricity and marineelectrical systems, and as such, is an active memberof the ABYC’s Electrical Committee. And yes, Edholds an ABYC Electrical Certification!

The first edition of Powerboater’s Guide to Elec-trical Systems has been read and used as a referencedocument by tens of thousands of marine profes-sionals, technicians, students, and boating enthusi-asts. It is considered a “must-have” reference guidebecause it is able to convey concepts and practicalknowledge of complex material in a user-friendlymanner. It speaks to both the technically minded aswell as to the novice boatowner. It also stresses the

importance of adhering to industry standards in or-der to “do the job right the first time.”

The second edition has new information, takesa fresh look at industry technological advances, andcaptures the essence of what you need to know re-garding electricity and electrical systems used onboats, yachts, and marine craft. It discusses the ba-sics as well as advanced techniques concerningmaintenance, troubleshooting, and repair of marineelectrical systems. More importantly, it does all thisin the context of the latest ABYC standards, whichhave significantly evolved and changed since thepublication of the first edition.

In closing, as a friend and work associate, EdSherman can be counted upon to give you candidand sage advice and expert counsel. I look to him tohelp shape and guide the future of the ABYC andour education, training, and certification programs.He’s a team player who is looking out for the indus-try and the boaters we serve, and as such, has his eyeon the end goal—safer boats for safe, fun, and mem-orable boating experiences for all. I encourage youto read, digest, understand, and use the material inthe second edition of Powerboater’s Guide to Electri-cal Systems—you’ll be glad you did!

Skip BurdonPresident and CEO,

American Boat & Yacht Council

F O R E W O R D T O T H E S E C O N D E D I T I O N

www.abyc.com

ix

Preface to the Second Edition

Since the first edition of the Powerboater’s Guide toElectrical Systems was published in 2000, there havebeen many evolutionary and some revolutionarychanges to marine electrical systems, and significantupdates to the standards that dictate how designersand field personnel should carry out their work. Thebasics of marine electrical system troubleshootinghaven’t changed much, but certainly some of theequipment we install and use has. This second edi-tion of the Powerboater’s Guide reflects these changesand provides an update to where we are in 2007. Ex-amples of some of the new material found withinthis second edition include complete reference up-dates to all the applicable ABYC electrical standards.Since the first edition notable changes have beenmade to both the ABYC AC and DC standards inthat what were once Standards E-8 and E-9 are nowcombined into Standard E-11. The ABYC batterystandard has some significant changes within it andthey are discussed here. We’ve also seen a majorchange in ABYC Standard A-28, Galvanic Isolators,which now requires a status-monitoring system tobe integral with the isolator; that information hasbeen added to this edition.

Additionally, and not standards based, we’veseen some major improvements in both batterytechnology and battery combiner systems. Compo-nents that used to rely on either fully mechanical orelectromechanical control have gone completelysolid-state, and have added intelligence built in toprovide much more accurate control of multiplebattery systems. New information is provided hereabout this new era of battery control.

In the area of engine-specific electrical systems,we’ve moved from traditional distributor ignitionsystems on gas engines to computer-controlled DIS

(distributorless ignition systems). Flat serpentinedrive belts used to run engine-driven alternators arenow the norm rather than an anomaly, so some ad-ditional information has been provided relative tothe maintenance of these very important drive belts.

Next, we are now seeing the broad use of net-worked engine con-trol systems fromsuch companies asMercury Marine withits SmartCraft system,and Teleflex with asimilar system. Theuse of these systemswill ultimately sim-plify things, but fornow it looks dauntingto the untrained eye.Now we’re distribut-ing data from onepoint to another inaddition to basic electrical distribution. We’ll discussthese changes in chapter 10.

Additionally, we’re just beginning to see entireelectrical systems that are reduced to many fewerwires from such companies as Paneltronics, with itsPowerSign System, and Capi2’s three-wire system.These systems go beyond the scope of this book, butmy book Advanced Marine Electrics and ElectronicsTroubleshooting covers them in more detail.

Finally, we’ve seen the increased use of alter-native energy systems, specifically solar panels, oncruising powerboats. The need-to-know informa-tion relative to these systems is provided in thissecond edition.


x

This book has been evolving in my head for years.Of all the different areas I work in, diesel and out-board engine mechanics and onboard systems, elec-tricity is one of the most interesting as well as oneof the most perplexing to many people. Even boatingprofessionals who have worked in and around wa-

tercraft all theirlives sometimesfind the funda-mental princi-ples of electricitydifficult to un-derstand. Elec-tricity is oftenseen as a myste-rious force that,

except when it shows itself in a spark or in the fluc-tuation of the needle or dancing digits of a multi-meter, is invisible in a controlled state. The effects ofelectricity, however, can be quite profound, as any-one who has inadvertently bridged the terminals ofa freshly charged battery or latched onto the wrongwires in a hot AC circuit can attest.

I was fortunate in that I recognized the arcane andslightly magical qualities of electricity early in my ca-reer, and this gave me a distinct advantage over mycolleagues. As a teacher and practitioner of the elec-trical arts as well as a mechanic, I was forced into adeeper comprehension of the underlying principlesof electricity. In order to teach others the fundamen-tals of electricity, I had to translate the technicalmumbo-jumbo, that obscure language that’s so pop-ular with the technophiles and engineers who writemost of our electrical manuals, into plain English—first so I could understand it myself, and then so Icould help others to understand it. The very act oftranslating electrical technobabble into English andrewriting it into plain, simple explanations got meon my way as a technical writer.

I first became involved with electricity as an au-

tomobile mechanic about 30 years ago. The automo-tive electrical systems of those days were fairly simple,and I spent most of my time troubleshooting faultycomponents and repairing factory-engineered wiringharnesses. The wiring diagrams we had back thenshowed in minute detail the complete electrical sys-tem for each make and model of automobile, andthese diagrams were readily available and easy to un-derstand.

When I became involved with boats, however,things changed dramatically. Before the formationof the American Boat & Yacht Council, Inc. (theABYC, which I talk about much more later on),electrical anarchy reigned unchecked in the marinefield. There were no uniform standards, no univer-sal system of color coding, and no governing bodyto bring order to the prevailing chaos. Boatbuildersdeveloped their own, largely proprietary wiring sys-tems, and technicians and owners alike madechanges and additions without restraint of reason orcommon standards. Boats were often one-of-a-kindor limited production, and customers frequently or-dered extra or specialized equipment added after theboat had been built and the electrical wiring in-stalled. Many entire electrical systems were createdby self-trained technicians who had even less experi-ence in designing reliable and safe marine systemsthan I myself had at the time. Problems with thesedo-it-yourself electrical systems were many, and fre-quently I found myself reengineering work that hadbeen improperly, poorly, and sometimes dangerouslyinstalled. Wiring diagrams, when they were availableat all (which wasn’t often), were rudimentary and of-ten inaccurate to the point of being useless. Uniformcolor-coding of wiring was nonexistent.

I spent quite a few years muddling about withthese perplexing and difficult-to-understand electri-cal systems, and I was lucky enough not to burn upanyone’s boat or to make too many other disastrousmistakes. Then I discovered the ABYC and became

� ABYCTo find out more about the ABYC, contact themat 613 Third Street, Suite 10; Annapolis, Mary-land 21403; Phone: 410-990-4460; Fax:410-990-4466; www.abyc.com.

Introduction


www.abyc.com

xi

familiar with its comprehensive Standards and Tech-nical Information Reports for Small Craft. Suddenly,my work as a marine electrician became much eas-ier. I now had uniform electrical standards to workwith and to learn from. Information on wire types,insulation materials, color codes, and wire sizingwas clearly laid out and understandable even tothose of us with limited training and experience. Thehearsay, guesswork, and old wives’ tales that haddominated the old school were no longer a part ofmy work. I had found, at last, a guiding light to leadmy electrical efforts through the dark jungle ofnaïveté and ignorance.

The good news for boaters is that today moreand more boatbuilders are building their craft to theABYC standards, and a genuine effort is being madeindustry-wide to improve owners’ manuals andwiring diagrams so that they can be more easily un-derstood by engineers and laypersons alike. Thistrend toward universal standards of marine electri-cal work has also had a profound effect on the ex-pertise of all professional marine technicians, fromthe person who designs the boat right down to theone who changes your oil and checks the gap in yourspark plugs. This includes you, the boatowner. Onceyou finish this book and develop a few of the ana-lytical skills we will cover in the following pages,your comfort level when working with things elec-trical will be increased dramatically.

The Powerboater’s Guide to Electrical Systems isnot intended to turn you into an expert electrician.It should, however, help you wade through the tech-nical mumbo-jumbo and electro-speak that you’rebound to encounter in your other reading on ma-rine electricity. Once you understand the basics,much of the rest will follow in a clear, concise, andeasy-to-understand manner. All instructions andrecommendations found in this guide are in accor-dance with the very latest of the ABYC’s electricalstandards, and the procedures described herein haveall been tried and tested many times over by me per-

sonally and by my students. Many of the tests andprocedures that I have detailed here are identical tothose used in my curriculum for the ABYC’s elec-trical technician certification program.

By following the recommendations in this guideyou will be taking a long step toward keeping yourboat’s electrical system in top working order. Then,in those rare instances when a failure does occur, theprocedures outlined here will get you to the sourceof the problem quickly and easily so that you caneffect repairs and be back underway without thestress and frustration normally associated with elec-trical problems.

There are several points in this book where Iclearly state that a professional marine electricianshould be called in or consulted for certain com-plicated, difficult, or dangerous operations. Some ofthese procedures require either specialized equip-ment or expertise (and often both) that goes far be-yond the scope of this book. Please do not takethese warnings lightly or fail to heed them. Expen-sive and delicate electronic equipment can be dam-aged and even destroyed by improper installationand repair techniques, and the high-voltage AC sys-tem on your boat can be extremely dangerous ifproper procedures are not understood and followedto the letter. Household AC current when misap-plied to a human body is unpleasant in the best ofcircumstances, and in the worst it is lethal. Extremecare must be taken any time your boat is pluggedin to shore power, has a generator running, or hasan operational inverter on board. If, after readingthrough chapter 11 of this book, you still don’t feelconfident in your abilities to sensibly and safely per-form the tests and procedures I have outlined, youshould stay away from the AC service on your boat.

I hope you enjoy the Powerboater’s Guide to Electrical Systems and find it a useful addition toyour arsenal of onboard tools.

As always, good luck, and happy boating!

I N T R O D U C T I O N

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What Is Electricity?One of the first things to confront a new student ofelectricity is the concept of just what the stuff is. Weall know that electricity travels through wires, butwhen we inspect a cut cross section of one of thesewires we see nothing more than copper, and the ideaof anything passing through it, as water passesthrough a hose, seems quite impossible. The classictextbook definition of electricity, translated fromelectro-speak into plain English, states that electric-ity is the flow of electrons through a conductor froma negatively charged material into a positivelycharged material. Nature abhors a vacuum, and thepositively charged material, which has been strippedof electrons by one of several generating processes, isjust that. We have all felt the shock of static electric-ity after shuffling our bare feet across a wool rug:Electrons stripped off the rug by the friction of ourfeet build up in our body; then, when we grab thedoorknob, the circuit is completed, the excess elec-trons rush back into the carpet, and we get a jolt(sometimes quite a strong jolt) of electricity.

Over the years many analogies have been con-trived to explain the electricity phenomenon—noneof which is entirely satisfactory. One such analogycompares electricity to a tank of water with a hoseattached, and another compares it to a looped tubefull of Ping-Pong balls that endlessly push eachother around in a circle. Yet another uses horses gal-loping around a racetrack to try to help us visualizeelectrons racing around an electrical circuit. Whileall of these picturesque analogies help to explainsome aspect of electricity (comparing a battery to awater tank, for example, works quite well), nonedoes a good job of explaining them all.

In the following pages, we break electricity downinto its fundamental elements; then, once an under-standing of each of these elements has been estab-

lished, we put them together into the finished prod-uct. We proceed slowly and collect and study all thecomponent parts; then, once we have a good under-standing of them, we assemble them into a completepicture. Those readers who already have a good graspof the basic principles of electricity will find some ofthe following to be repetitious, but bear with me—even those of us who work in marine electricity everyday will benefit from a good review of the funda-mentals. Let’s start with a brief discussion of the mostbasic of all electrical components—the circuit.

Electrical CircuitsElectrical circuits are just what they say they are—circles or loops of conductive material that allow anelectrical impulse to flow around and around in anendless orbit. This conductive material is most oftencopper wire but it can actually be nearly any mater-ial. In an automobile the engine block and chassisare critical parts of many circuits. At home the veryearth your house is sitting on is a part of the electri-cal circuit and is essential for the correct operationof your pop-up toaster and your television set.That’s why one prong on all your electrical plugs iscalled the ground.

There are several types of electrical circuits withwhich we will want to become familiar. However,regardless of type, the essential elements of a circuitwill always be the same.

� All circuits on a boat need a source of electrical

power; it could be a battery, your municipal

power through a shore-power connection, a gen-

erator, an engine-driven alternator, a solar panel,

or a wind-driven turbine. It can even be (with cat-

astrophic results) the chemical reaction between

your aluminum outdrive and the bronze props

on that big sportfisherman in the next slip.

Electrical Basics You Need to Know

1

Chapter 1


� You’ll also need an electrical conductor or a series

of conductors so arranged that electrical energy can

travel from the source to the place where it’s needed

(to the light bulb in the galley, for example), then

back again to the source. As I mentioned above,

nearly anything can serve as a conductor; even the

air we breathe (normally an excellent insulator)

serves as a conductor when the charge of electrical

energy is massive enough—as anyone who has wit-

nessed the flash of a lightning bolt can attest.

� Although they are not required to make an electri-

cal circuit function, there is a practical requirement

in most circuits for a fuse or circuit breaker. Circuit

protectors defend circuits from destructive forces

of excessive amperage, a subject we will deal with in

some detail later on.

� Also not required but present in most circuits is some

sort of switch to turn the electrical energy in the cir-

cuit on and off or to direct it to the place where we

want it to go to work for us. Sometimes the circuit

breaker serves as a switch, but there are many other

types of switches that we will discuss later on.

� Finally, all functional electrical circuits need some

sort of load or appliance. The circuit load is both

the reason for the circuit’s existence and the single

most important element that makes it possible for

the circuit to exist. The load can be a light bulb or

the depth-sounder or the stereo system that con-

verts the electrical energy flowing through the cir-

cuit into something useful—light, information for

safe navigation, or pleasant and relaxing music.

The load also serves to control the unrestricted

flow of electrons that would otherwise destroy the

circuit and even burn up your boat in the process.

Remember this one simple fact: whenever wehave an electrical problem on board our boats, wecan always trace the problem to a fault with one orsometimes more of these basic elements. Figure 1-1shows the elements discussed above in a normal se-quence as might be found on your own boat. Whenthe switch we show here is turned on (referred to asclosed in electro-speak), we can see the completeroute that our friends the electrons have to follow. Ifyou follow the guidelines in this book, like those elec-trons follow that circuit, you’ll soon be tracingthrough all manner of circuits yourself, and whenyou develop trouble spots, you will, in all cases, beable to find them without difficulty.

Circuits Found on Your BoatIn all of electrical engineering there are only two ba-sic types of circuits common to boat use, and yourboat, no matter how simple its electrical systemmight be, will use both in abundance. These are the

parallel and series circuits. Actu-ally, there is a third type, but it’sreally only a combination of thefirst two, called, appropriatelyenough, a series-parallel circuit. Aclear understanding of what hap-pens in each of the circuit types aselectrons flow through them willgo a long way toward helping usto think out problems which willundoubtedly arise later. Let’s takea close look at these three types ofcircuits one at a time, but first weneed to understand the differ-ences between marine circuits andothers, such as those found inyour family car.

2

POWERBOATER’S GUIDE TO ELECTRICAL SYSTEMS

Load

CircuitProtector

Battery

Switch

Fig. 1-1. The basic circuit, showing the key elements.

Marine versus Automotive CircuitsOne of the most common mistakes that many proudowners of new powerboats make is to try to save a fewdollars by installing inexpensive automotive acces-sories in place of more expensive marine accessories.After all, it doesn’t really matter if that new readinglight in the forepeak is designed for a boat or an RV,does it? I mean, a light is a light, right? Wrong!

Even the best-made and most costly automotiveaccessories are not really appropriate for installationin boats, not so much because of the accessories asbecause of the circuits to which they will be attached.Most automotive equipment is made from mild steelor will have major components made from somehighly corrosive material, but this is not what con-cerns us here. If you take a close look at that readinglight, for example, you’ll find that those designed forcampers will have a single wire (usually referred to inelectro-speak as a lead) and those designed for boatswill have two.

Automobiles commonly use what are called chas-sis ground circuits where the metal frame of the car—the chassis—or the engine block serves as the secondwire of the circuit and provides a path for the electri-cal current to flow back to the battery. On a boat thissimply doesn’t work. The fiberglass hull of the typi-cal powerboat is a very poor conductor of electricity,and on steel and aluminumboats an electrical currentpassing through the hullcauses all sorts of problems,the most important ofwhich is severe corrosion.Thus, nearly all marine acces-sories will have two leads,and the second wire com-pletes the circuit back to thebattery. Also, the best ma-rine accessories are heavilyconstructed of noncorrosivematerials and are designedto function in the hostilemarine environment.

OK, now that we under-stand the differences between

boat stuff and car stuff (and have resolved to never putcar stuff in our boat), let’s get back to our three ba-sic circuit types.

Series CircuitsThe simplest of circuit types is the series circuit, widelyused on your boat to supply electricity to single loads,such as a cabin fan or bilge pump. With this circuittype, there is only one path for electrical current flow.Figure 1-2 depicts a simple series circuit. The inher-ent problem with this circuit type is that it cannot beused effectively on board to service more than oneelectrical appliance. Figure 1-3 on page 4 shows a se-ries circuit with three cabin lights installed. As you cansee, the electrical current must flow through one be-fore it can get to the second, then through the secondbefore it can get to the third. The problem with thiscircuit is that as electrical current flows through eachload, it’s doing work for us (making a light bulb glow,for example), and each of the loads in the series circuitmust share the available power. So the available volt-age at the source—in this case, the 12-volt battery—gets divided by each of the loads. In the example shownin figure 1-3, assuming that each of the light bulbs hasthe same wattage, the voltage drop across each bulb willbe one third of the available 12 volts, or 4 volts each.Thus if the bulbs are engineered to run on a 12-voltsource, each will glow more dimly than designed.

3


Cabin Light

Battery

CircuitProtector

Switch “On”

Fig.1-2. A simple series circuit with only one load.

There is still another fundamental flaw in any se-ries circuit that’s expected to carry more than a singleload: If any one of the electrical loads should fail inthe open position (that is, break the circuit, as whena light bulb or a fuse blows), the flow of currentthrough the circuit will cease, shutting all the otherappliances down as well.

Parallel CircuitsParallel circuits, such as the one in figure 1-4, solveboth problems we have with the series circuit byproviding more than one path through which elec-trons can flow, which means that each load on thecircuit receives the samevoltage as all the others.This arrangement has threeobvious advantages: first, itallows all the appliances onthe circuit to share a singlepair of leads from the bat-tery and a single fuse or cir-cuit breaker; second, eachload or appliance will havedirect access to battery volt-age so that it can do its jobwith peak efficiency; andthird, if one appliance onthe circuit should fail in anopen condition (electro-

speak for a broken circuit),the other appliances cancarry on with their jobs.

Parallel circuits are clearlysuperior to series circuits anytime multiple loads, such asseveral cabin lights or navi-gation lights, are served byone pair of wires and onemain circuit protector.

Series-Parallel CircuitsSeries-parallel circuits arenothing more than complex(sometimes very complex)combinations of series and

parallel circuits. In the real world of marine electricalsystems, most of the circuits found on our boats areactually series-parallel circuits because they combinecomponents wired in series, like switches and fuses, inthe primary feed of the circuit, and at some otherpoint loads are wired in parallel. Certain components(such as switches and fuses) of many actual circuitsare usually wired in series regardless of the type ofcircuit they serve, while most appliances that share acircuit are wired in parallel. Figure 1-5 illustrates thisarrangement.

The important thing to remember here is thatthe voltage available to the loads wired in the par-

4


Battery

Cabin Light Cabin Light Cabin Light

CircuitProtector

Switch “On”

Fig. 1-3. A series circuit with three electrical loads. Note that with this circuittype, there is only one path for electrical current flow.

Fig. 1-4. A typical parallel circuit. In a parallel circuit, there is more than one pathfor electrical current flow.

Battery Cabin Light Cabin Light Cabin Light

CircuitProtector

Switch “On”

allel section of the cir-cuit will be quite close tothe voltage at the begin-ning of the circuit. It’snot too hard to see thatby using series-parallelcircuits, manufacturerscan save a lot of moneyon switches, wire, andcircuit protectors, butseries-parallel circuitsalso greatly simplify aboat’s overall electricalsystem, with no sacrificein performance or safety.

Ohm’s Law and What It Can Tell UsGeorg Simon Ohm (1787–1854), a German physi-cist, was one of the great early experimenters withelectricity. He left us with the simple but oh-so-im-portant mathematical formula that bears his name.Ohm’s law helps us to understand the relationshipbetween the measurable forces in electricity. Oncewe are armed with a clear understanding of the re-lationships between the different elements in thisformula, we will have made a giant step forward inour ability to understand and locate electrical prob-lems.

As we work with this invisible thing called elec-tricity, we need to get used to dealing in an abstractway with the stuff. We’ll be taking a lot of mea-surements with a multimeter, and we will learn totranslate these measurements into meaningful in-formation. Throughout the rest of this book Idemonstrate the correct methods of obtaining ac-curate electrical measurements with a multimeter,and I try to provide an understanding of what thesemeasurements mean. First, however, we must getthe definitions of a few electrical terms clear in ourheads, and then become completely familiar withthis wonderful thing called Ohm’s law.

The Key PlayersThere are four terms that will continually crop up inany discussion of things electrical: volts, amps, ohms,and watts. Each of these terms represents an electricalvalue and is named after an early experimenter inelectricity. These are the people who captured theconcept of electricity and made it useful to people likeyou and me who own boats. There is a fifth term, alsonamed after an early experimenter, that’s gainingfavor with the knowledgeable and trendy among us,the joule.

The unit of electrical resistance, the ohm, wasnamed for Georg Ohm, the German scientist whogave us Ohm’s law. The electrical symbol used to ex-press the value for ohms is the Greek letter omega,shown in figure 1-6 on page 6. When used in Ohm’slaw, however, resistance is represented by a capital R.

Alessandro Volta (1745–1827) was an Italianphysicist who gave us the unit of electrical forcecalled the volt. The electrical symbol for volts is sosimple that it doesn’t need an illustration; it’s just acapital V. However, when used in the formula forOhm’s law, voltage is represented by a capital P,which stands for potential.

5


Battery

Switch “On”

Cabin Light Cabin Light

CircuitProtector

Switch “On”

Switch “On” Switch “On”

Cabin Light

Fig. 1-5. A series-parallel circuit as found on your boat.

Andre-Marie Ampere(1775–1836) was a Frenchphysicist whose namesakeis the electrical unit that de-scribes the rate of electricalflow through a circuit thatwe call the amp. The elec-trical symbol for amps is acapital A. When workingwith Ohm’s law, we use acapital I for amps.

James Watt (1736–1819) was a Scots mathe-matician credited with sig-

nificant improvements of steam engines who coined theword “horsepower” to measure the amount of work amachine is doing. Horsepower is fine for measuringlarge amounts of energy, but it doesn’t work for thesmall amounts that we have to measure while workingwith electricity, so, in honor of this ancient Scot, we callthe electrical unit of power a watt and use a capital E torepresent it. Watts aren’t used in the formula for Ohm’slaw, but they are important in a corollary to Ohm’s law,called the pie formula (because P × I = E, as we will soonsee), that we will be using to calculate the size of wiresand circuit protection.

James Joule (1818–1889) was an English chemistcredited with the discovery that heat is a form of en-ergy. Thus, a joule is a unit of electrical energy equalto the amount of work done (or heat generated) bya current of 1 amp acting for 1 second against a re-sistance of 1 ohm. The symbol for a joule is a J and italso is not used in Ohm’s law calculations. Joulesaren’t really important for the work that we dothroughout the rest of this book. I wouldn’t evenmention them here if it weren’t for the fact that thejoule is gradually replacing the watt in some areas ofelectricity (joule is also replacing calorie in the list ofnutritional information on many food packages) andthat you’ll probably run into it in your other read-ing. When you do hear the term, you’re fairly safe inassuming that 1 joule = 1 watt.

So you can see that our foundations of electricityare named after quite an interesting internationalrogues’ gallery of electrical scientists.

Let’s forget about joules for now and take a lookat each of these other terms more closely, and per-haps we can begin to get a clearer picture of their importance to us.

VoltageVoltage is the measure of the potential that an electri-cal power source has for doing work for us. Thus, afully charged 12-volt battery has the potential of pro-ducing 12 volts (actually closer to 13.5 volts) of power.In fact, the term electrical potential is often used insteadof the word voltage and means the same thing. To referback to the analogy of the water tank, where a hoseconnected to the bottom of a tank might measure 100pounds per square inch (psi) of water pressure, a wireconnected to a 12-volt battery (in a circuit, of course)will measure 13.5 volts of electrical potential. In bothcases we are referring to the energy that’s available todo work and nothing else; the voltage in the battery isexactly the same concept as the water pressure in thetank. Simply think of voltage as electrical pressure. Thehigher the voltage in the battery (or in any othersource of electrical power), the more pressure is avail-able to send electricity along its path in a circuit.

AmperageAmperage is often confused with voltage, and I thinkit’s the most difficult of all our definitions to grasp.Think of amperage as the rate of electrical flow pasta given point in a circuit. If you can think of voltageas electrical pressure, then it should be easy to thinkof amps as the volume of electrical energy flowingthrough a point in a circuit. Amperage is most im-portant in my mind because too much of it in a cir-cuit is what trips circuit breakers, blows fuses, meltswires and other components, and sometimes burnsup boats. This stuff needs to be carefully controlled,and much of the rest of this book will be devoted tounderstanding how to do just that.

ResistanceResistance, as we said, is measured in ohms and is thatinvisible force that holds back electrical flow (amper-age) and reduces the electrical potential (voltage) aselectrical energy flows through a circuit. It’s also theelectrical unit that puts electricity to work for us. For

6


Fi 1 6Fig. 1-6. The ohm sym-bol, the Greek omega.

example, it’s the resistance in the element of a lightbulb or the toaster in your kitchen that makes the el-ement glow and give off light or toast your bread.And it is the rapidly fluctuating resistance in micro-scopic transistors (measured in tiny fractions of anohm) that makes the wonderful world of marineelectronics possible. In marine wiring, unwanted orexcessive resistance is caused by such things as looseor corroded connections, wire that is too small indiameter, or wire runs that are too long.

One noticeable by-product of resistance to elec-trical flow is heat. In the case of the toaster, we haveengineered a way to make this heat useful. In the caseof a loose or corroded connection, the heat generatedis sure to cause damage to the area around the con-nection; read melted switches and plug connections.Figure 1-7 illustrates Mr. Ohm’s formula.

Ohm’s LawNo, you don’t have to worry about going to jail forbreaking Ohm’s law. In fact, you can’t break it (notwithout a nuclear particle accelerator that costs manymillions of dollars), because it is, for all practical pur-poses, inviolate—you couldn’t break it if you tried. Sim-ply stated, Ohm’s law is a mathematical formula we canuse to calculate any one of the values we mention aboveas long as we know the value of any two of the first three.For example, if we know the amperage and resistancefor a circuit, we can easily calculate the voltage, or if weknow the voltage and amperage, Ohm’s law gives usthe resistance. Once we know the amperage and thevoltage, we can calculate the wattage using a simple lit-tle formula, called the pie formula, that we will get to ina moment (“Working with the Numbers”).

It’s important to note here that various versions ofthe following formulas exist, assigning different letterdesignations to the elements of the formula (E forvolts or sometimes watts, for example; the letter I isoften used to designate amperage as well). The pointis that it really doesn’t matter what letter you use, aslong as you know which value it’s assigned to. For ourpurposes we’ll keep it simple and use V for volts, A foramps, W for watts, and R for resistance or ohms. Fig-ure 1-8 on page 8 shows the simple equation used tofind watts, or amps if voltage and wattage are given.

Ohm’s law works out rather nicely for us asboaters because we will always be able to measure atleast two of the values we need to calculate the third.Voltage (V) and amperage (A) are both easily mea-sured using a basic multimeter, and we will learn howto do this later. With some circuits, ohms (R) are alittle tricky to measure accurately, but we’ll learn howto handle them also. For our purposes, wattage (W)is not measured but calculated from voltage and am-perage, or information often provided by the appli-ance manufacturer.

7


Fig. 1-7. The Ohm’s law equation. This circle providesa visual relationship between the key electrical players.If any two of the values are known, the third can befound by using either multiplication or division. Bymultiplying amps times ohms, voltage can be found.By dividing voltage by ohms, amperage can be found.Dividing volts by amps determines resistance (ohms).Notice that if voltage remains constant and if resis-tance increases, reduce amperage flow and vice versa.This explains mathematically why a short circuit toground, before power reaches a load (resistance), is sodangerous. Amperage will go way up until either afuse blows or a breaker trips, or something burns up!Conversely, it also explains why, if resistance increases(loose connections, too small a wire), amperageneeded by the appliance won’t be delivered.

Working with the NumbersA quick look at Ohm’s law and the pie formula, pre-sented above, and some brief experimentation witha few actual numbers illustrate the interrelationshipof all the elements we have discussed so far. As withany algebraic formula, we can move and substitutevalues so that we can use the same formula, writtendifferent ways, to determine any of our electrical val-ues as follows:

� V = A × R, or volts equal amps multiplied by ohms.

� A = V ÷ R, or amps equal volts divided by ohms.

� R = V ÷ A, or ohms equal volts divided by amps.

With the pie formula we get the following three variations:

� W = V ×A, or watts equal volts multiplied by amps.

� A = W ÷ V, or amps equal watts divided by volts.

� V = W ÷ A, or volts equal watts divided by amps.

So, assuming a 13.5-volt constant (the normalvoltage in a charged 12-volt battery), let’s see whathappens to amperage when the resistance in a cir-cuit changes from, say, 5.5 ohms to 7.8 ohms. By di-viding 13.5 volts by 5.5 ohms we see that theamperage draw through this circuit will be 2.6 amps.By increasing the circuit resistance to 7.8 ohms, wewill end up with 1.73 amps.

If the resistance in a circuit is known or if it canbe accurately measured, we can apply this simple for-mula as the first step in determining what size circuitbreaker or fuse to use. (See chapter 4 for more detailon circuit protectors and how to select them.) As theresistance in a circuit goes up in value, the amperagegoes down. Conversely, as resistance goes down, am-perage goes up. This trade-off between amps andohms is always valid, regardless of the amperage andresistance, as long as the voltage remains constant.

As for a practical application of the pie formula,it’s quite useful when you’re adding AC appliances toyour boat. All Underwriters Laboratories (UL) ap-proved appliances must have a tag or label affixed tothem with the operating voltage and wattage of theappliance clearly stated. By applying the pie formula,and dividing the wattage by the voltage, we can de-termine how many amps the appliance will requirefor operation.

With DC appliances, determining the amperageused by the load is always the first step in determiningthe size of the fuse or circuit breaker we will need andthe size of the wire we will use to supply the circuit.

Voltage DropVoltage drop is simply the reduction of voltage in acircuit caused by amperage working to overcome re-sistance, and represents the conversion of electricalenergy to some other form of energy. For example,when you turn on a bilge pump the current (amper-age) used by the pump converts the power wattage tomechanical energy that turns the impeller of yourpump and keeps your bilge dry. In another, less

8


Fig. 1-8. The power formula. Like the Ohm’s lawequation, the power equation can be used to determinethe third value if two are known. Multiply and dividejust as with Ohm’s law. This is the “pie formula,”which is useful for determining AC amperage. All UL-rated (Underwriters Laboratory) appliances musthave either volts and watts or volts and amps indi-cated on an attached sticker. The sticker is useful forsizing circuit breakers and wire size.

desirable example, when current encounters resis-tance (ohms) in a circuit caused by wiring that is toosmall or by corroded terminals, the wattage is con-verted to heat (wattage is more properly called jouleshere) that can blow fuses and trip circuit breakers.In extreme cases it can destroy your boat.

In both cases, the reduction in voltage from thebeginning of the circuit at the positive terminal of thebattery to the end of the circuit at the negative ter-minal is called the voltage drop. Normally, voltagedrop is referred to as a percentage that we get by di-viding the original voltage into the amount of thedrop. Thus, a circuit measuring 13.5 volts at the pos-itive terminal and 12 volts at the negative terminal(we will discover how to make these measurementslater on) will be experiencing a 1.5-volt or 11.1 per-cent voltage drop.

Putting It All TogetherSome basic facts relative to what happens to resis-tance, voltage, and amperage as they are dispersedthroughout the different circuit types are in order.In other words, it’s time to assemble our monster.

Beginning with the series circuit, remember thatthere is only one path for electrons to flow through-out the circuit. Here’s what happens: as amperage(which you’ll recall is the volume of electrical energyflowing through a circuit) travels through the circuit,voltage (the electrical potential) is used up and re-duced as the current (amperage) encounters resis-tance (ohms) and is converted to power (wattage).This reduction in voltage is referred to as voltagedrop. The sum of the individual voltage drops mea-sured at each component in a series circuit is equal tothe original source voltage. The total circuit resis-tance in a series circuit is the sum of the individualresistance values of each load (resistance) in the cir-cuit. The same amperage will flow through each re-sistance in a series circuit but the voltage is dividedand shared by the loads in the circuit.

In the parallel circuit, there is more than one pathfor electrons to follow, and this changes the charac-teristics of the circuit considerably. First, havingmore than one path reduces the inherent circuit re-

sistance. The total circuit resistance in a parallel cir-cuit will always be lower than the resistance for anysingle resistance in the circuit. Current (amperage)will vary as it feeds each individual resistance in thecircuit to the extent that the resistance values are dif-ferent. The total circuit current in amps will be thesum of the current drawn at each load in the circuit.

Circuit Problems and How They OccurIn my years of listening to people talk about electric-ity, I’ve learned one thing for sure. To the uniniti-ated, every time anything goes wrong with theirelectrical system, it’s described as a “short.” Althoughthis is certainly possible, the truth is that most prob-lems that occur with electrical systems on boats arenot short circuits. In fact, a more probable cause forelectrical trouble on a boat is caused by the unwantedopen or interrupted circuit, already mentioned. So,what are the common problems, and what are someof their causes and characteristics?

Open CircuitsAn open circuit is one that contains a break or openin the continuous path, or route, for electron flowdescribed earlier. This can be caused by a break in thewiring, a connection that has come undone, or cor-rosion that accumulates to the point where the volt-age drop is so great that current will no longer flow inthe circuit. By comparison, a “wanted” open occurswhen you switch off an electrical device. The switcheffectively breaks the continuity through the circuit.

To pinpoint unwanted opens in a circuit you mustattack them systematically with your multimeter, andwe will learn just how to do this in a later chapter.

Short CircuitsShort circuits are just that, circuits that have beenshortened from their original design. Shorts, as theyare commonly called, are almost always induced byhuman error and come in three varieties.

Shorts to GroundThe first of the three is the short circuit to ground.With this condition, the wire to the electrical load

9


(the feed) has somehow connected itself directly toground before reaching the appliance. In a short toground, the resistance in the circuit (which you’ll re-member is essential for a circuit to operate) has beencircumvented. As Ohm’s law will tell you if you workthrough the numbers, a lot of amperage will flowwith only the resistance of the wire to stop it. Thegood news: If the circuit is designed correctly, thefuse or circuit breaker will trip. The bad news: Somewire and insulation may be burned before the cir-cuit protection opens the circuit.

Intercircuit ShortsThe second variety of short is what I refer to as the in-tercircuit short. With this type, two or more electricalcircuits will be affected simultaneously. The cause?Drilling through a wiring harness to install new deckgear and then running a screw down through thedeck into the harness, effectively connecting multiplecircuit wires. This short circuit with a screw is quitecommon. Another frequent cause for this type ofshort is not thinking dynamically. Remember, ourelectrical system will change when the engine is run-ning and while we are underway. Wiring harnessesthat rub against moving pulleys, hot exhaust mani-folds, and the like are electrical time bombs. Check tobe sure all wiring is properly secured and clearancefrom moving machinery is adequate.

Internal ShortsThe third and final short circuit type we will discussis the internal short, a short circuit that can occurdeep within the internal circuitry of the electrical appliance itself. This type of short circuit is the most

harmless of the three because it doesn’t usuallythreaten the safety of our boats. Internal shorts can,however, be expensive to correct because they oftenmean that expensive equipment will have to go intothe repair shop or worse, into the dumpster. Often ashort inside a piece of equipment will simply causethe equipment to stop functioning. At other timesthe fuse or circuit breaker will trip without the riskof burned wires or insulation (assuming the circuitprotection is rated properly).

ToolsMost of us will already have a good collection of ba-sic tools. However, besides our regular collection ofsockets, spanner wrenches, screwdrivers, pliers, andthe like we’ll need to acquire a few more specificitems. Once we start working with electricity and be-gin performing serious electrical troubleshootingprocedures and upgrades, we are going to need spe-cialized equipment that will allow us to work safelyand do a proper job.

Figure 1-9, a photo of my personal collection oftools, shows some of this equipment.

Technology has been good to us electricians in thelast several years, and significant improvements intools and equipment have been made, specifically inthe areas of multimeters and crimping tools (we takea closer look at these in chapters 3 and 4). As you gothrough this book, you’ll see these tools in use, withspecific instructions for every test procedure you’llever need on board your boat.

10


11


A

B

C

D E

F

G

H

IJ

K

Fig. 1-9. Some basic and not-so-basic electrical tools from my collection. Beginning at the lower left and movingclockwise are (A) wire stripper, (B) cable cutter, (C) ratcheting crimping tool, (D) inexpensive Snap-On induc-tive ammeters, (E) Fluke 36 high-amperage inductive multimeter (true RMS), (F) miscellaneous jumper leadsused for various tests, (G) the Ancor/Prova inductive ammeter with frequency scale, (H) AC probe pen, (I) ACLED socket (outlet) tester, (J) Snap-On ignition spark tester, (K) 12 V test light/probe.

Working with Wiring Diagrams

12

The Trouble with BoatsIn chapter 1 I mentioned that I first started work-ing with electricity in the automotive trade and itwasn’t until later that I became involved with boats.One of the first things that I learned while workingon cars was the value of a good wiring diagram.With a glance at a sheet of paper covered with linesand squiggles and a plethora of other arcane hiero-glyphics, I could tell immediately what went whereand how. When something went wrong, I could tellfrom a quick study of the diagram what the mostlikely cause of the problem might be and where togo to fix it. Naturally, when I switched to the marinefield and started working on boats, the first thing Idid was reach for the trusty wiring diagram.

Alas, there were no wiring diagrams, at least nonethat were comparable to those I had been accus-tomed to. Troubleshooting a defective electrical sys-tem, which had been so straightforward withautomobiles, became a study in frustration and con-fusion. Just locating components and determiningwhich wire did what became a job for InspectorSherlock and his trusty Watson, or in this case, In-spector Sherman and his trusty multimeter.

Until only recently, boatbuilders generally havedone a rather poor job of creating usable wiring dia-grams for their products. Some supply only partialdiagrams, while others don’t supply any at all or simplypass on to the buyer the one provided by the enginebuilder. On the other hand, some builders go to theopposite extreme and provide diagrams that aremasterpieces, but you have to be an electrical engi-neer to interpret them. They are far too complicatedto be very useful for the occasional boater/electricianand can even be confusing for the professional.

An electrician working on a car with a decentwiring diagram can usually go directly to an electri-cal problem and fix it with a minimum of fuss andtime. However, that same electrician working on a

boat is quite likely to spend half or even more of hisor her time just trying to figure out how the systemsare wired. Manufacturers and boatbuilders outdothemselves, it seems, in the creative way they locatecomponents in obscure lockers and hide wiring inunlikely places.

To further complicate the situation, many ma-rine components, such as radios, radar, and naviga-tion instruments, are installed by the distributor ordealer and not by the boatbuilder or manufacturer.If you’re buying a used boat, you can bet that thereare numerous components installed by the previousowner, who may or may not have known anythingabout electricity. You can also bet that even if yournew boat came with a comprehensive wiring dia-gram, none of these aftermarket add-ons are evernoted on it.

With the cost of a boatyard electrician well pastthe $100-an-hour mark in some areas, it’s easy to seewhy electrical repair bills can get so high. With everyjob done at the boatyard, a substantial portion of thebill goes toward paying the electrician to figure outthe wiring system. Thus, learning to do your ownelectrical work is one of the most cost-effective waysthat you, as a boatowner, can spend a few hours.Once you finish this book you’ll be able to makeyour own basic repairs and additions. You may evenpay for the book with your first job.

As a first step in becoming a competent marineelectrician you should draw up your own wiringdiagram for your boat, if you don’t already haveone. If you do have a wiring diagram, it’s verylikely that you can make significant improvementswith just a few revisions and additions, and it’s thepurpose of this chapter to show you how to dothis. Follow the advice given here and you’ll bewell on your way toward understanding whatwiring diagrams are telling you, and you’ll be ableto properly upgrade your diagram as you add newequipment to your boat.

Chapter 2


Wiring DiagramsA wiring diagram, sometimes referred to as a schematicdiagram, is a wonderful tool often compared to a roadmap. Suppose you were to find yourself in Salt LakeCity for the first time and you were trying to get yournew Ranger bassboat to Lake Mead to give her a spin.The first thing you would be likely to do is reach for aroad map. Salt Lake City would be clearly shown onthe map with graphic symbols that might tell you notonly its location but its relative size, elevation, and inspecial cases, things like its political and racial demo-graphics. Lake Mead would likewise be shown withgraphics that would contain a lot of information aboutthe lake such as its size, shape, pool elevation, and any-thing else the mapmaker thought was important. Thelines connecting the city to the lake would representroads, of course, but you could also tell by the natureof the lines what the roads would be like: paved or dirt,straight or twisty, single-lane, double-lane, divided,or interstate. You would also see intersections, junc-tions, detours, and areas of potential trouble and con-gestion. To see what the varioussymbols and graphics mean youwould look at the key or legend,which is usually provided on a cor-ner or on the back of a map.

The wiring diagram you’re go-ing to develop or improve for yourboat is just like that road map. Itwill provide us with the informa-tion to trace a route from start tofinish, in this case the electrical flowthrough the circuits on your boat.The trouble is, unlike road maps,which are reasonably consistent indesign and have that prominentkey to tell you what the symbolsmean, wiring diagrams come in avariety of designs and styles, andthere is seldom a key to reference.Fortunately, most of the basic elec-trical symbols are fairly standardand the others that you’ll need forour wiring diagram aren’t too hard

to figure out. Before we do anything else, let’s take alook at a few of the more common electrical symbolsthat you’re likely to encounter on any standard wiringdiagram.

Common SymbolsLike road maps, wiring diagrams use a variety ofsymbols to indicate different components within anelectrical circuit. Electrical engineers are trained torecognize several thousand of these symbols and tounderstand just what they mean. This gives wiringdiagrams a certain consistency. To the untrained eye,however, these symbols can be as cryptic as an an-cient Chinese manuscript.

Figure 2-1 illustrates some of the symbols mostfrequently used in marine wiring diagrams.

Elements of a Good Wiring DiagramA wiring diagram should be laid out just like a roadmap and will incorporate many of the features of a

13


Conductors,no connection

Switch (SPST)single-polesingle-throw

Dioderectifier

Fuse

Circuitbreaker

Switch (DPST)double-polesingle-throw

a.

b.

Conductors,connected

Battery, single cellor voltage source

Battery,multi-cell

Capacitor

Resistor

Variableresistor

Light bulb(lamp)

a.

b.

Switch (SPDT)single-poledouble-throw

Switch (PBNO)push-buttonnormally open

Ammeter

Voltmeter

Voltmeter

Motor

Earthground

Equipmentor ground

a.

b.

Fig. 2-1. Common wiring diagram symbols.

14


good map. Some of the most important elements of agood wiring diagram are as follows:

� Every wiring diagram for a small boat should be

simple enough to be easily read and understood,

even by those of us who don’t have an engineering

degree.

� The relative location of all electrical components

on the boat must be shown.

� Each component of each circuit must be shown

with all relevant specifications.

� The size and the type of the fuse or circuit breaker

used in each circuit must be clearly indicated.

� Each wire to and from each component in the boat

must be identified on the diagram by color and

number or label, depending on how this marking is

applied.

� The gauge of every wire in each circuit should be

shown.

Figure 2-2 shows an example of a diagram with allthe elements described above.

Figure 2-3 shows a far less descriptive diagram,which was the norm for years. (This one may look alot like the one that came with your boat.)

Component IdentificationIf you’re new to marine electrical systems, one of thefirst things you should do is learn to identify thewiring and the major components of a circuit. Get-ting a positive ID on such items as bilge blowers, bilgepumps, and cabin lights is easy because you can tellwhat they do just by looking at them, but what aboutthe other required components in the circuit? Whereare they, and how can you begin to determine whichwires feed what circuits as you look at the multitudeof choices behind your distribution panel?

Figure 2-4 shows the back of a typical master dis-tribution panel, with all the key components identi-fied. For a further explanation of what these

S D

ALARM (2)

(NOT

E F

COLOR CODES:B - BLACKBL - BLUEBR - BROWND - DARKG - GREENGY - GRAYLT - LIGHT

O - ORANGEP - PINKPU - PURPLER - REDT - TANW - WHITEY - YELLOW

SYMBOLS:

SWITCH DPST

SWITCH SPST

FUSE

CONNECTION

NO CONNECTION

DC GROUND

PLUG

NOTES: (1) START CIRCUIT NEUTRAL SAFETY AND EMERGENCY SHUTDOWN SWITCHES LOCATED AT SHIFTER.

(2) SOME EQUIPMENT MAY NOT BE INSTALLED ON ALL MODELS

(3) FUSEBLOCK POWER SUPPLIED BY ENGINE MOUNTED CIRCUIT BREAKER

(4) SOME ITEMS MAY HAVE SECONDARY OVERCURRENT PROTECTION AT THE UNIT.

FUEL VOLT TEMP OIL TACH (2)

TR

AIL

ER

SW

ITC

H

TR

IMS

WT

ICH

10A

10A

10A

5A

5A

10A

10A

15A

10 GA R-PU BATTERY B+ .10 GA BR-W TRIM SENDER14 GA Y-R START .14 GA PU IGNITION .10 GA B GROUND .16 GA GY-BA TACH SENDER16 GA LT-BL OIL SENDER .16 GA T TEMP SENDER16 GA T-BL ALARM .16 GA R-PU TR IM POWER16GA C-W T R I M / T R L RDOWN14 GA PU-W T R I M U P . 10 GA B;-W TRAILER UP .

BATTERYTILT/TURNMOTOR

ENGINEWIRING

HARNESS

16 GA BR

16 GA D-BL

16 GA BR

16 GA GA Y

16 GA G

16 GA D-8L

16 GA BL 16 GA GY-BL16

16 GA GYL

16 GA G

16 GA GAY

16 GA BR

16 GA D-BL

16 GA BR-W

ALLAROUNDLIGHT

NAVAGATIONLIGHT

HORN

BILGE PUMP

BLOWER

CABIN LIGHT

LIVE WELLPUMP (2)(4)

STEREO (4)

16 GAR

AN

TE

NN

A

Fig. 2-2. A good wiring diagram with all of my listed key elements incorporated.

15


components do, refer to the glossary at the back ofthis book.

Wire Identification and the ABYCColor CodeIdentifying the wires that connect the various compo-nents illustrated by a wiring diagram can sometimesbe a challenge when you first get started. The goodnews here, however, is that our friends at the ABYChave developed a standard color code for boat wiringthat brings order to this previously mind-bogglingtask. This color-coding scheme, which has beenaround for twenty-odd years, is finally catching on.

The ABYC color code assigns a specific color ofwire to each function in a properly wired marineelectrical system. Thus, an electrician who is work-ing on a boat wired to the ABYC standard and is con-fronted with a dark blue wire knows immediatelythat that wire is for the interior lights and nothingelse. He or she also knows that the purple wire is forthe ignition system, and that all those red and yellowwires are the DC-positive and -negative connectors.This standard makes it easy to identify a wire’s func-tion in the system on any boat, not just your own,even without the help of a wiring diagram.

Fig. 2-3

OPT. ACOUTLET

OPT. ACOUTLET

OPT. ACOUTLET

OPT. SHORE

OPT. ACOUTLET

MASTERSWITCH OPT. NO.2 BATTERY

SHORE POWERBREAKER SWITCH

Negative Bus Bars

Circuit Breakers/ Switches

Positive Bus Bars

Fig. 2-3. A typical, poor-quality diagram. This is all that came with a sailboat that I purchased in the early 1980s to describethe electrical installation. The problem is certainly not exclusive to sailboats!

Fig. 2-4. A switch panel with key components identified.

16


Fig. 2-5. ABYC-recommended color codes from their E-11 standard. (Courtesy ABYC)

17


Figure 2-5 at left lists the ABYC’s recommendedcolor codes and the circuits (or parts of circuits) theyserve, as found in Standards and Technical Informa-tion Reports, Standard E-11, tables 14 and 15. If yourboat is wired to the ABYC’s recommended standards,you can get a jump start in deciphering what you seebehind your distribution panel by using this table.

By now you may be saying to yourself, “Hey, thisis great—but wait, as I look behind my distributionpanel I see 20 red wires and 20 yellow ones [or blackones on an older boat] and several each of about adozen other colors. What do all these wires do andwhich one feeds which circuit?” All you know fromthe table above is that the yellow (or black) wires aresupposed to be DC-negative conductors, the red onesshould be DC-positive conductors, green ones areground wires, and light blue ones are for the instru-ments. But as you sort through this spaghetti, how doyou tell just exactly what each wire does? Your boatmay not use the ABYC-recommended colors in itswiring, or it may only use some of them. Also, as withmost changes, initial acceptance of the color-codingstandard when first introduced was neither univer-sal nor overwhelming. Most manufacturers have im-plemented the changes gradually as they updatedtheir assembly procedures and as stocks of existingwire were depleted. Also, it’s important to note thatthe ABYC standard allows for deviation from the rec-ommended color scheme as long as all wiring is iden-tified in some way. Many builders have adopted anumbering scheme that positively identifies any wirewith numbered labels affixed to the wire; a wiringdiagram for the boat then lists the numbers and iden-tifies them. The standard also allows for color sub-stitution as long as a wiring diagram is supplied toidentify the wires positively.

If you own one of these older boats or a new onethat doesn’t comply with the ABYC color-codingstandard, the only answer is to go through the entireelectrical system and write down the color and func-tion of each wire. This isn’t as hard as it sounds, andI show you how to do it at the end of this chapter.

Fortunately, compliance with the standard is nownearly universal, and the odds are that if you’re buy-ing a new boat, both the boatbuilder and the enginemanufacturer will have complied. This is good news,

of course, but even if your wiring system is in com-pliance with the ABYC recommendations and youhave a comprehensive wiring diagram, you stilldon’t know what all those multicolored wires inback of the distribution panel do. This brings us tocircuit identification, a procedure that’s a little dif-ferent than wire identification.

Circuit IdentificationCircuit identification will help you to determine thespecific function of each wire in back of your switchor circuit-breaker panel (which, for consistency, let’scall the distribution panel) or any wire on the boatfor that matter. There are several accepted methodsfor identifying circuits, but unless the manufacturerof your boat was unusually considerate, you’ll have tocome up with a system and install it yourself. Thetechnique is called “wire chasing” in electro-speak,and it simply involves following a specific wire fromone end to the other and placing some means ofidentification on the wire as you go.

First learn to concentrate on the circuit in ques-tion; forget about all those other wires for the timebeing. Fortunately, circuit identification is one of theeasiest ways to become familiar with the details ofyour system. Here are a few methods you can use.

Numbered LabelsOn the off chance the manufacturer of your boat wasunusually meticulous and provided circuit identifica-tion, this is the method they probably used to do it.Numbered circuit ID labels come in pads available inany electrical supply house. They are simply clear plas-tic peel-and-stick labels with white or black numbers

� A Note on Engine-maker Compliance and the ABYC Color CodeIt's important to note that the ABYC standards are recommendations only,and should not be confused with the National Electric Code (NEC), themandatory safety standards for land-based electrical installations devel-oped and published by the National Fire Protection Association (NFPA).Mercury Marine is one of the few engine manufacturers that actually fol-lows the ABYC-recommended color codes. But since all engine makersprovide comprehensive wiring diagrams with their products, they are stillcompliant with ABYC standards.

18


printed on them (black for the white and light-col-ored wires, and white for the black and dark-coloredwires). To use them, first identify the circuit youwant to label by the nameplate on the front of thedistribution panel adjacent to the switch or circuitbreaker. (It will probably say something generic like“accessories.”) There are usually five or six labels ofeach number in a set, so all you need do is place anumber on the first wire behind the switch panel,then trace the wire to the fixtures that it operates.Place labels at strategic places along the wire as yougo. Next, trace the yellow or black wire back to thecommon bus (which should be located somewherenear the distribution panel) and label it the sameway. Now write that circuit number down someplacehandy and move to the next circuit. If you alreadyhave a wiring diagram, you should also write the newcircuit number on the corresponding circuit on thediagram.

Now you know that the circuit on the switchpanel marked “accessories” is circuit number 32 andit feeds the light in the forepeak and the exhaust fanin the head. If either if these appliances should stopworking, all you need do is trace wire number 32 un-til you find the problem.

Named LabelsSeveral manufacturers make label sets that you canuse just like the numbered labels. They simply statejust what fixture or fixtures a specific circuit operates.Named labels have the advantage of not requiring akey to translate the number into a function, but theyalso have several disadvantages. For one thing, theyare not as neat and tidy as the numbered labels, andmost circuits will have more than one function, re-quiring more than one label. You can get around thislast objection by simply writing your own labels onwhite electrical tape with a permanent marker andwrapping it around the wire, but it still is a bit messy,especially on large or complex systems. The labelsalso tend to fall off if exposed to solvents or fumes.

Colored Heat-Shrink TubingA great way to identify circuits is to provide each onewith its individual color code applied with heat-shrink tubing. By using two colors for each circuit,

you can ID up to 25 separate circuits with only fiveseparate colors; if you use three colors for each circuit,the total number of circuits jumps to 125. The bigdrawback to this system is that each wire must bedisconnected at both ends before the heat-shrinkcan be applied, so it’s very labor-intensive when ap-plied to an existing system. However, it’s fine foradditions to existing systems and when a boat mustbe completely rewired.

Colored Tape and Wire TiesYou can, of course, apply the same color designationas described above using colored electrical tape,which is easy to apply without disconnecting any ofthe wires. The trouble with tape is that it isn’t aspermanent as heat-shrink and it’s liable to wash offif exposed to fuel, solvents, or lubricants (such asWD-40). You can do the same thing using coloredwire ties, which are a little bit messier but tend to bemore permanent.

There are many other methods for wire identifi-cation that are acceptable and are often used by bothboat builders and owners. The ABYC standard onlystates that some means of identifying the wires ineach circuit should be employed. All of the abovemethods are quite acceptable and are good alterna-tives for any work you may do, such as adding onnew equipment.

Whatever means of circuit identification you select—numbered or named labels, colored heat-shrink tubing or tape, or a new one that you think upfor yourself—of this you can be sure: knowing whatevery wire on our boat does, where it goes, and whereit comes from is going to make your boating life muchsimpler when problems crop up.

Substituting Wire ColorsBefore we leave this fascinating discussion of com-ponent identification, we need to cover one othersituation that might arise while you’re working onyour new ABYC-compliant wiring system. What ifyou need to replace the 14-gauge brown wire thatconnects your generator to the alternator, and theonly colors you have in your tool box are orangeand yellow? This brown wire is only 3 feet long, andthe electrical supply house which might or might

19


not have it in stock is 45 minutes away. What doyou do?

Often, one or more of the various colors forwiring to the ABYC recommendations may not bereadily available at the time you perform a repair,and substitution may be the only practical solution.It’s perfectly OK to use one of the other colors pro-vided you code both ends of the replacement wirewith the proper color and then make a prominentnote on the wiring diagram. The best code mediumin this case is colored heat-shrink tubing, but, ofcourse, brown heat-shrink is less likely to be availablethan brown wire. In this case you could make do witha written label wrapped around the wire and pro-tected with waterproof tape. When you substitutewire colors, circuit ID becomes doubly important.

Expanding the Basic CircuitExpanding the elements of the basic circuit to includethe components shown in figure 2-6, you end upwith something that looks very much as it might lookif it were wired on your boat, even though this mightbe hard to see in this compressed state. In this dia-gram, I am illustrating what the wiring for a bilgeblower circuit would look like if we backtracked tothe master switch panel on the boat.

Figure 2-7 on page 20 illustrates what the powersupply circuit to a master switch panel should looklike, with a circuit protector (fuse or breaker) andbattery master switch installed. I should point out,however, that many boats do not use a battery masterswitch, and many installations don’t have the fuse orbreaker installed either. The latest version of theABYC’s electrical standard E-11 states that “A batteryswitch shall be installed in the positive conductor orconductors from each battery or battery bank with aCCA rating greater than 800 amperes.”

You’ll have a lot more information on batteriesand battery banks in chapter 5. For the moment, suf-fice to say that many small runabouts with only onesmall battery could easily fall below this 800-ampthreshold, and would be exempt from the recommen-dation for a battery switch. I should also point out thateven though switches are not recommended for these

small batteries, 800 CCAs is more than enough currentto start a fire and cause serious burns in the event of ashort. Thus, a means of quickly disconnecting thesesmall batteries is no less important than it is for the bigguys, in my mind. All batteries, regardless of CCA rat-ing, should have a master shut-off switch.

Chasing CircuitsRemember that the distribution panel (or panels—sometimes there are more than one) on your boat isthe point at which most of the circuits on your boatcome together in close proximity, and the situation

Negative Bus Bars

Circuit Breakers/ Switches

Positive Bus Bars

Bilge Blower

Showing positiveand negativereturn wiresthrough switchpanel

Fig. 2-6. A bilge blower circuit highlighted on the switchpanel, with the key components identified. When looking atlarge clusters of wires in an arrangement like this, it’s impor-tant to focus on only the components and wires that are im-portant to you at the moment. To begin your search, start atthe wiring at the back of the switch or breaker labeled“blower” in this example and carefully tug on the wire to fol-low it through any bundling at the back of the panel. Onceyou’ve identified all the wiring behind the panel, locate thecomponent in question on your boat. A good wiring diagrammay indicate a relative component location on the boat, butdon’t count on it: usually you have to search on your own tofind all the components in a given circuit.

always looks a lot worse than it really is. Once youlearn what a basic circuit looks like and develop thehabit of ignoring everything but that one circuityou’re working on, all that spaghetti will start tomake sense, and everyday repairs will come easilyand quickly.

For example, suppose one Sunday morning youdecide to take the old Donzi for a run out to Block Is-land to buy the kids and some friends a pizza. It’s abeautiful sunny day with a flat-calm sea and not acloud in the sky. It’s the perfect day for a familycruise—the kind of day you bought your boat for.You back the trailer down the ramp like an expert,slide the old girl off the trailer with the panache oflong practice, lower the out-drives, and hit theblower switch to clear the engine compartment ofany gasoline fumes prior to starting the engines.Nothing happens. Nada, zip, zero.

Without the blower you can’t safely (or legally)start your engines. No engines, no Block Island. NoBlock Island, no pizza. You aren’t going to be a verypopular guy, and what has started out to be a perfectday on the water is rapidly deteriorating into a first-class disaster. What to do? Lucky for you, you boughtthis book and know exactly what to do.

The first thing you’ll do, of course, is to check thestate of the battery charge and all the terminals. Onceyou have determined that everything is as it shouldbe here, move to the distribution panel and check thefuse or the circuit breaker for the bilge blower. Nowmove to the switch on the panel identified (hope-fully) as the blower switch and trace the two wiresfrom there to the connection on the distributionpanel. Then trace the wires from the switch to theblower motor itself.

Aha! Look there—right where the blower leadsemerge from the engine compartment bulkhead. Seethat white powder on the terminal block? It’s copperoxide and it’s a sure sign of corrosion. Sure enough, aclose inspection shows a terminal that’s completelyengulfed in the stuff. First, make sure the blowerswitch is turned off. Then remove the terminal with ascrewdriver, then a quick scrape with your trustypocket knife takes care of the corrosion. Once the ter-minal is cleaned and reattached, the blower is as goodas new, and you’re soon blasting over the wavesthinking of nothing but pepperoni, mushrooms, andmozzarella cheese. The day is saved, and instead of aschmuck you’re a hero. Plus you probably savedyourself enough in repair bills to at least pay for thepizza.

Figure 2-6 on page 19 illustrates what you mustfocus on when confronted with an electrical problemof this magnitude. The highlighted areas of thisdrawing are the only things you should be thinkingabout as you try to troubleshoot a problem with thisbilge blower circuit. Looking at figure 2-8, you cansee what this might look like on a typical wiring dia-gram (the dotted line represents the proper circuit),with each element of the circuit identified. Trackdown and check out each of the basic elements de-scribed in chapter 1, and you’ll quickly locate thetrouble with any circuit.

Locating ComponentsA common trick for boatbuilders, especially on mid-to larger-sized boats, is to install remote junctionboxes for wiring. They really do this to simplify theelectrical system and to save money on wiring, but it

20


BatteryMasterSwitch

Panel BoardFeeder WireCircuitProtector

Fig. 2-7. A proper power supply circuit to the switch panelshowing the circuit protector (fuse or breaker) and the bat-tery master switch.

21


S D

ALARM (2)

(NOT

E F

COLOR CODES:B - BLACKBL - BLUEBR - BROWND - DARKG - GREENGY - GRAYLT - LIGHT

O - ORANGEP - PINKPU - PURPLER - REDT - TANW - WHITEY - YELLOW

SYMBOLS:

SWITCH DPST

SWITCH SPST

FUSE

CONNECTION

NO CONNECTION

DC GROUND

PLUG

NOTES: (1) START CIRCUIT NEUTRAL SAFETY AND EMERGENCY SHUTDOWN SWITCHES LOCATED AT SHIFTER.

(2) SOME EQUIPMENT MAY NOT BE INSTALLED ON ALL MODELS

(3) FUSEBLOCK POWER SUPPLIED BY ENGINE MOUNTED CIRCUIT BREAKER

(4) SOME ITEMS MAY HAVE SECONDARY OVERCURRENT PROTECTION AT THE UNIT.

FUEL VOLT TEMP OIL TACH (2)

TR

AIL

ER

SW

ITC

H

TR

IMS

WT

ICH

10A

10A

10A

5A

5A

10A

10A

15A

10 GA R-PU BATTERY B+ .10 GA BR-W TRIM SENDER14 GA Y-R START .14 GA PU IGNITION .10 GA B GROUND .16 GA GY-BA TACH SENDER16 GA LT-BL OIL SENDER .16 GA T TEMP SENDER16 GA T-BL ALARM .16 GA R-PU TR IM POWER16GA C-W T R I M / T R L RDOWN14 GA PU-W T R I M U P . 10 GA B;-W TRAILER UP .

BATTERYTILT/TURNMOTOR

ENGINEWIRING

HARNESS

16 GA BR

16 GA D-BL

16 GA BR

16 GA GA Y

16 GA G

16 GA D-8L

16 GA BL 16 GA GY-BL16

16 GA GYL

16 GA G

16 GA GAY

16 GA BR

16 GA D-BL

16 GA BR-W

ALLAROUNDLIGHT

NAVAGATIONLIGHT

HORN

BILGE PUMP

BLOWER

CABIN LIGHT

LIVE WELLPUMP (2)(4)

STEREO (4)

16 GAR

AN

TE

NN

A

Fig. 2-8. How the bilge blower circuit would look on a good-quality wiring diagram.

often seems like they do it just to confound us poorelectricians. The problem isn’t with the use of thejunction boxes—they usually make a lot of sense.The problem is where the boatbuilders choose to lo-cate them. I have found them inside lockers, underfloorboards, behind drawers and medicine cabinets,over headliners, and I even found one behind a hold-ing tank where I couldn’t get to it without a lot of un-pleasant pumping. These terminals are often locatedin spots so obscure that you would never find themwithout the help of some kind of wiring diagramshowing their exact location—even then, they cansometimes be hard to find.

Hidden junction boxes can often be the sourceof a loose or broken connection in a circuit and mustbe found before the faulty circuit can be put backinto service.

The first thing you do once you find one of theselost junction boxes is to note its location on thewiring diagram for the future reference of the next

poor slob who has to work on the boat. I don’t haveany way of telling how much time I have wasted overthe years emptying out lockers and pulling up floor-boards trying to find one of these elusive connectionpoints, but I know that it’s a lot.

Figure 2-9 shows one of these junctions, carefullyhidden.

Locating WiresAnother common problem you will encounter as abeginning marine electrician is the mysterious case ofthe vanishing wires. Often wires exit the distributionpanel only to disappear behind a cosmetic bulkheador cabinet. Worse yet, they vanish into a molded-inconduit on the inside of the hull, only to reappear atthe component itself. The wiring can travel the entirelength of the boat without leaving a single clue as towhat may be going on between the distribution paneland the light fixture, or whatever other component isin question. This is another case where a good wiring

diagram can make all the difference in the world be-cause it will show how the wiring for each circuit isrouted through the boat. A comprehensive diagramwill even indicate where any of those elusive hiddenjunction boxes may be located.

Drawing Your Own Wiring DiagramNow that you know how to chase wires and to iden-tify components and devices, it’s time to draw up aninclusive and detailed diagram of the electrical sys-tem on your boat. Drawing a new diagram is easierthan you think, although it’s time-consuming. If youhave a large boat with a complex system it’s best todivide the project up into several sessions of severalhours each. If you don’t like the way your drawing

comes out the first time, don’t be afraid to do it overuntil you get it just the way you want it. Even if youhave a good diagram already, it isn’t a bad idea tomake up a new one. There is no better way to learnfirsthand about all the little intricacies and idiosyn-crasies of your electrical system than to trace each cir-cuit and write it down in a diagram.

SubsystemsThe first step in drawing your new wiring diagram isto mentally divide the electrical system into subsys-tems. These might logically be the charging and start-ing subsystem, the ignition and engine subsystem,the console-navigation subsystem, the lighting sub-system, and the house or utilities subsystem. Anotherway to do the same thing is to divide your boat phys-ically with each division labeled as a subsystem sothat the head, galley, forepeak, engine compartment,and anything else that’s appropriate for your boat be-comes a subsystem. The actual division will dependon the size and the kind of boat you have, but you getthe idea. Next get three or four large (11- by 14-inchis ideal) sheets of graph paper for each of your sub-systems (you’ll be doing each one over several times)and a large clipboard or a piece of plywood to writeon. Write the name of each subsystem on a separatesheet of the paper.

The Rough DraftFor your first draft you’re going to make a separatediagram for each subsystem. You’ll put them back to-gether for the final if you like, but for now it’s a loteasier to keep the systems in order if you keep themseparate in your mind’s eye, hence the separate sheetsof paper. As a logical first step, let’s start with thecharging and starting circuit; it’s one of the simplestbut also one of the most important.

First draw a sketch of the battery symbol as it’sshown in figure 2-1 on page 13, for each of the bat-teries on your boat. Now label each battery with allthe pertinent information you have available. Thismight include the cold-cranking amps and the amp-hours, if you know these things (much more aboutbatteries will come later), but at a minimum it will be

22


Fig. 2-9. A wiring harness junction located inside a locker.Not only are these difficult to find at times, but many areuninsulated, as shown here. Don’t pile all your tools intothis one! A short circuit is sure to occur across the terminals.

the nominal voltage—either 6 or 12 volts—for each.The next step is to draw in the battery cables just asthey appear on your batteries. For now, just worryabout the cables that connect the batteries to eachother and ignore the others. Double-check to makesure you have the polarity right—that all the positiveand negative terminals are labeled correctly. Now addto your drawing any battery isolators, isolationswitches, or any other paraphernalia you find con-nected directly to the battery. If you find a mysteriouscomponent you can’t identify, just make a little draw-ing of what it looks like and keep going. You’ll haveplenty of time to come back and fill in the blanks whenyou figure out just what that mystery contraption is.

Once you have drawn the batteries and the di-rectly connected cables, move to your battery isola-tion switch and draw a rough sketch of it somewherenear the middle of your diagram. (If your drawingbecomes too messy or you run out of room, simplytrace the lines you want to keep onto a clean sheet ofpaper. Get used to the idea of redrawing yourwork—you’ll be doing it many times.) A typicalswitch has four positions; label them on your dia-gram just as they appear on your switch, probably“No. 1,” “No. 2,” “both,” and “off”. (Complex sys-tems might have two or more of these switches.)Now connect the switch to the battery on the dia-gram just as it’s connected on your boat, and don’tforget to include the fuses, using the fuse symbolshown in figure 2-1, that should be connected to thepositive battery leads somewhere between the batter-ies and the switch.

Now that you have the positive side of your bat-tery system drawn it’s time to fill in the negative side.Find where all the negative battery cables are con-nected at a common point on your boat. This couldbe on a separate stud, on a heavy-duty terminal strip,or on an engine or transmission bolt. Draw this onyour diagram roughly as you find it on your boat,once again sketching in any mysterious componentsthat you find attached but can’t identify.

The next step is to locate on your boat the startermotor, the alternator, and the voltage regulator. Ifyou can’t find a voltage regulator, you most likelyhave an alternator with an internal regulator. Draw

little pictures of these items on your diagram, makingsure that you provide terminals for all the wires yousee attached to each. Next draw a three-terminalswitch that will represent your starter key switch.These little drawings needn’t be fancy; just a littlerectangle identified with a label will be fine.

Now that you have the alternator, the starter, thestart switch, and perhaps the voltage regulator drawnon your diagram, follow each wire that’s connectedto each item on your boat and draw it on the diagramjust as you find it. Don’t forget to write down thecolor of the wire, the gauge, if you can tell what it is(sometimes the gauge is written on the wire; more onthis later), and the circuit ID number or code, if yourboat has one. Trace each wire for its entire length,and when you come to a switch, fuse, circuit breaker,or any other device that you may or may not be ableto identify, draw that in too. When you encounterwires that leave this particular subsystem and go toanother, such as the ones connected to the accessoryposition on your starter switch, show them going offthe page and label their destination (“to radio,” “toalarm system,” or whatever is appropriate). If youcan’t tell where one of these wires goes, just label itwith a question mark for now.

You may not believe this, but you now have a roughdraft of your wiring diagram for your starter andcharging subsystem. Once you redraw it, it should looksomething like the one in figure 2-2. If it still doesn’tlook like much, don’t worry as long as you can look atthe drawing and relate all your little sketches and sym-bols to actual components on your boat.

Now that you understand how the process works,you can work your way through each of the subsys-tems on your boat. If you have a large or an unusu-ally complex boat, this will take a lot of time, butkeep at it. Eventually you’ll have a complete, albeitcrude, drawing of each of your subsystems. Gothrough these drawings one at a time and make sureyou have at least a tentative understanding of whatyou have done. Convert any of your rough sketchesof components to the proper symbols as shown infigure 2-1 if you can, but the important thing is thatyou know what your figures represent. If you findone or two that are still confusing, just retrace the

23


wires on your boat (it will be much easier the secondtime around) until you understand what you havewritten down. It’s now time to put it all together in afinal drawing.

The Final DraftIf you have done a good job with your rough draft,the final draft is optional. A well-done rough drawingis often more than adequate for use as a workingwiring diagram and more than enough for mostworking electricians. Any professional electricianworking on your boat will love you forever for yourefforts in drawing up the rough draft just because youhave made his or her life so much easier. There is alsoan advantage to keeping all your subsystems on sep-arate sheets, because as you make additions andchanges to your boat you can redraw each subsystemas it becomes necessary.

If, however, you’re the fastidious type and wouldlike a more professional and finished look for your di-agram, there are several ways to accomplish this. Theeasiest approach is to buy an electrical engineer’sstencil at any well-equipped art supply store and useit to render your rough sketches into a finished draw-ing. These stencils come in a myriad of styles andhave hundreds of electrical symbols on them. Eitherthe stencil for basic DC systems or one designed for

automotive applications will do just fine. Once youhave the stencil, it’s a simple though time-consum-ing matter of converting your crude sketches into apolished drawing with all the proper symbols. Stillanother method, which most true professionals areusing today, is to use a computer graphics program toacomplish the same task. The only problem with thisapproach is that unless you’re using a sophisticatedprogram such as AutoCAD, which has a substantialsymbols library, you’ll find yourself having to createyour own symbols. These don’t have to be compli-cated, however; as long as they’re properly labeled,any unique shape will suffice.

If you want to carry the finished copy of your elec-trical diagram to a ridiculous extreme, you can takeyour roughs to an electrical engineering firm. If youpromise to leave a substantial portion of your mater-ial wealth with them, they will have your sketchesrendered into a computer-generated schematic thatwill be worthy of framing and hanging over your fire-place. They might even review your work and pointout your mistakes. Better yet, if you happen to knowa friendly electrical engineer or someone proficientwith electronic drafting, perhaps you can trade aweekend of chasing bluefish off Fire Island for a fin-ished set of drawings. After all, that would be fun, andisn’t having fun what powerboating is all about?

24


MultimetersA multimeter is a highly versatile measuring andtesting tool that will be essential for performing agreat many of the tests and procedures that we willbe covering in the rest of this book. It’s one of thefirst tools that you as an aspiring marine electricianwill need to buy, and it’s by far the most important.With your multimeter you’ll be able to make quickand accurate measurements of all elements of yourelectrical system, and you’ll rarely approach anyelectrical task without it in hand.

Back when I first started in electrical work, agood (and expensive) multimeter was already one ofthe most important tools in my toolbox. However,there are profound differences between the cumber-some multimeters of only a few years ago and thesleek digital marvels we have today. My first meterwas a 4-inch-thick, 6- by 8-inch black box, fes-tooned with knobs and terminals and a large whitedial with some six or eight scales printed on its face.In those days the better and more expensive a me-ter was, the larger it was, simply because a large ana-log scale is much more accurate and easier to readthan a small one. To use this beast I would select therange of the scale I wanted, set the function, zero orcalibrate the meter needle, connect the probes, andsay a short prayer that I had set the dials and con-nected the probes properly. Any mistakes, and themeter would make a little crackling sound, emit apuff of white smoke, and I would be holding a hand-ful of useless junk.

This is a bit of an exaggeration, of course, but thepoint is that the multimeters of just a few years agowere unwieldy, expensive, delicate, and hard to readand interpret. That expensive analog monster I usedin my early days as an electrician was not nearly asversatile and accurate as the most inexpensive digi-tal meter is today.

What a difference a few years makes! Huge

advances in multimeter technology and design havebrought us meters that are compact (the smallest isabout the same size as and only slightly thicker thana credit card), rugged, reliable, and so easy to readthat a novice can be using one with only a few min-utes of study. They are also cheaper than they usedto be: now a perfectly usable meter with somewhatlimited capabilities can be had for less than $20 atany Radio Shack, about two-thirds what an inex-pensive meter cost 20 years ago. Back when I boughtmy first multimeter, there were perhaps a dozen dif-ferent models from which to choose; today there arehundreds of different makes and models available tothe beginning electrician. In fact, there are so manydifferent multimeters on the market that selectingthe right one can be a bit daunting, and if you makethe wrong choice it can be an expensive mistake.Let’s take a little time to review the selection processso you get just the right one for you.

Selecting a MultimeterWithout a doubt, the most important decision you’llmake as you equip yourself for the electrical trou-bleshooting procedures we will visit in the forth-coming chapters is which multimeter to buy. Evenan inexpensive meter with limited capabilities willmake working on your electrical system much easierthan trying to do the job without one. In fact, manyof the tests we will be discussing are impossible with-out at least a basic multimeter. However, if youspend just a little more money and buy a meter witha few more advanced features, you can expand yourcapabilities considerably, allowing you to test formore things. But it’s just as easy to buy too muchmeter as it is to buy an inadequate one. The currentcrop of multimeters range from under $20 to overseveral thousand dollars in price. If you aren’t care-ful, you can spend a lot of money on fancy featuresthat you don’t need and will never use.

Selecting and Using a Multimeter

25

Chapter 3


Digital versus Analog MetersThe first decision you’ll have to make is between amultimeter with a digital display and one with ananalog display. There are still inexpensive (as well asexpensive) analog meters available for those few of uswho still prefer them. However, for general marinework a good digital meter is so far superior to theanalog models that the latter aren’t really worth con-sidering, regardless of any cost considerations.

The trouble with the inexpensive versions of theanalog meters is that they often have no internal cir-cuit protection, making it easy to destroy the meterif you connect it improperly. Further, many of thesemeters suffer from low impedance, or internal resis-tance, which reduces the sensitivity of the meter. Me-ter sensitivity is an important consideration for manyof the procedures outlined in this book.

Even with an expensive analog meter that’s con-nected correctly, it’s easy for a novice to make a mis-take in measurement because the analog dial isdifficult to read. These meters have adjustable scalesthat can be confusing to use and require the user tointerpolate values if the needle falls between two lineson the scale. Incorrect readings that are easy to makewith an analog meter are all but impossible to makewith a digital meter, even for a beginner.

There is a huge selection of digital multimetersavailable. The simple-to-follow specifications listedhere will help you to narrow down the field to exactlywhat you need.

Digital Features You NeedYou must make sure that the multimeter you se-lect has all the features you need for boat work. Beparticularly wary of some meters sold at the majorhome-supply stores, such as Home Depot, andresidential electrical supply houses. After a recenttour of several of these stores to see what multi-meters were available, I discovered that some ofthe meters they sell are designed just for homeuse. They are just fine for work with AC current athome, but they are limited in their DC measure-ment capability, a defect that renders them uselessfor onboard work. A typical multimeter suitablefor marine use will have a capacity of 600 to 1,000

amps in both the AC and DC modes, and it willhave resistance values up to 10,000 or 20,000ohms or even more.

Root-Mean-Square (RMS) MultimetersMost of the desirable features of your new multime-ter we will be discussing here apply to DC measure-ments, because that’s where you’ll be doing most ofyour work. There is one important feature, however,that applies only to alternating current, and that’s inthe way the multimeter reads AC voltage. Less-ex-pensive meters, called average-responding multime-ters, read AC voltage by averaging the peaks of thewave form (don’t worry, we discuss alternating cur-rent thoroughly in chapter 11), which can give erro-neous readings. Root-mean-square (RMS) meters usea formula that compensates for the valleys and peaksof the wave form (the root mean square of the maxi-mum amplitude of the wave) and gives a readingthat’s much closer to the actual usable voltage in thecircuit.

Average-responding meters will work just fine aslong as you’re measuring linear loads such as thosefound on incandescent lights, toaster ovens, and thelike. The problem comes when you try to measurecurrent on a non-linear load. In effect, this is any ACload that has some sort of solid-state control. Manyair conditioners and refrigeration systems fall intothis category. Depending upon the AC feed (shorepower, inverter, or generator), the error can be asmuch as 40 percent on the low side. This error has se-rious safety implications when you’re trying to deter-mine wire gauge and circuit-protection ratings. Thesimple solution, if you can afford it, is to buy theRMS meter if you’re going to be working around ACcurrent supplied by anything other than a shore-power connection.

If your boat is equipped with shore power andhas no inverter or generator, the less-expensive av-erage-responding meters will give adequate re-sults. (The difference between the AC powercreated by an inverter or a generator versus a shore-power connection will be discussed in chapter 11.)

Self-ScalingNo, the self-scaling feature doesn’t have anything to dowith cleaning fish (if they ever bring out a multimeter

26


that will do that, I will be first in line to buy one). Self-scaling (also called auto-ranging) simply means thatonce you select a function on your meter, the meterwill sense the magnitude of the function and set thescale accordingly. This important feature takes theguesswork out of selecting the correct voltage, resis-tance, or amperage to work with. For example, if youwanted to measure the value of a resistor with a me-ter that did not have self-scaling and you set the meterto the wrong scale, you would get a grossly incorrectreading. For certain functions, such as amperage andvoltage, if you set the scale incorrectly you might blowa fuse in the meter or even damage or destroy the me-ter. With self-scaling, the danger of selecting thewrong scale is greatly reduced, even though you muststill be careful selecting the function.

Diode CheckingThe diode-check function, as found on most of thebetter multimeters, is really only an ultrasensitiveand highly selective section of the resistance scale,but it’s a useful feature that adds virtually no costto the meter. Although it’s possible to check somediodes with a meter that does not have specificdiode-checking capability by setting the meter tothe lowest ohms scale, the reading that resultsshould never be counted on as accurate. To checka diode with a diode-checking meter, you test forcontinuity (see below) in one direction, then re-verse the probes and check again in the other di-rection. If the diode is working properly you’ll havecontinuity in one direction and not in the other.Diodes need a certain amount of current flowingthrough them to function, and the internal batter-ies of many meters without a diode-check functiondon’t provide enough current in the ohms scale toclose the diode. Often when a diode being checkedwith a meter using the regular ohms scale showsno continuity in both directions, the diode is finebut the meter just isn’t up to testing diodes. Theproblem is that you don’t have any way of tellingif the fault is with the diode or the meter. If you canonly afford one meter, make sure that it has diode-checking capability.

The diode scale will work with nearly any diode youmay encounter in marine work. The most common

diodes you’ll need to check are in your battery iso-lators, in your alternator, and on any solar panelsyou might be using to keep your batteries toppedup. We will talk more about diodes in a laterchapter.

Continuity AlarmBe sure to select a meter that has an audible alarmto indicate continuity on the ohms scale. Thisalarm usually consists of a high-pitched beep thatsignals the user that the meter is reading a resis-tance value lower than infinity. This simple featurereally comes in handy when you’re in a tight spotwhere you can barely connect two wires and can’tsee the face of your meter. Make sure that you canactually hear the signal. Some of the alarms usesuch a high pitch that those of us whose hearingisn’t perfect can’t detect it.

The alarm is used while checking for continuitythrough a circuit where the actual resistance in ohmsis of minor concern. Knowing for a fact that the cir-cuit you’re testing doesn’t have a break in it is all theinformation you’re after. An encouraging beep fromyour meter will give you that assurance.

Adequate AmperageOne essential difference among multimeters is intheir capability to read amperage on the DC scaleon a magnitude normally encountered in marineelectronics. Many expensive meters are capable ofreading amperage in tiny fractions of an amp. Someof these will read in milliamps (1 milliamp = 1/1,000of an amp) but will balk at reading anything over anamp. Most marine electrical gear, however, oper-ates at between half an amp (500 milliamps) andabout 8 amps, so it’s important that your meter beable to read in this range.

I consider the amperage-reading capability of amultimeter to be extremely high on the list of essen-tial features. Circuit breakers and fuses are both ratedby amps, and you need the capability of checkingthem. Selecting the correct wire gauge for a new pieceof equipment will involve an accurate measurementof both amps and volts. Excessive amperage in an un-dersized, improperly protected circuit is what burnsboats to the waterline.

27


For most of the electrical components on whichyou’ll be working, a meter that reads to 10 amps willdo the job. However, there are certain items onsome boats that will require a meter that readsmuch higher amperage. Anchor winches, startermotors, and alternators all require a meter thatmeasures in the hundreds of amps. When I amworking on any of these components I prefer the ca-pability of measuring amperage to values as high as600 amperes.

The less-expensive meters that only read amper-age in the milliamp range, usually up to about 500milliamps, are fine for electronic work, but they areuseless for onboard amperage readings. Slightlymore expensive meters will often read 10 or some-times as high as 20 amps, but they require that thecircuit be broken for connection of the meter (moreon that later).

Some meters that have a limited amperage scalecan read higher amperage using a shunt, a large, low-value resistor that bleeds a tiny amount of current offa high-amp circuit so that a low-amp meter can readit. Shunt meters are complicated to use and difficultto read, and so they aren’t really a consideration forus. However, you’re likely to find shunts perma-nently wired to the alternator circuit on boats thatuse amp gauges with high-amperage alternators.

Inductive PickupsIf you’ll be working a lot with high-amperage DC cir-cuits such as on a starter motor, electric windlass, oralternator, you’ll need a meter with an inductivepickup. These look just like a normal meter with ahuge crab-claw–like clamp on one end.

To measure voltage and resistance with an inductive-pickup meter, you use probes just like ona regular meter. The only difference is in the wayyou measure amperage. With a regular meter, youmust break the circuit on which you want to mea-sure the amperage, hook the probes up in series,and hope that the amperage doesn’t exceed the ca-pacity of the meter. If it does, there will likely besome fireworks (either a blown fuse or a blown me-ter). With the inductive meter, simply clamp thecrab claw around a wire, making sure the wire iscentered and oriented properly (if you get it back-

wards, you get a negative reading) and read the am-perage off the scale—no hassles disconnectingwires, and no fireworks.

A few of the better (more expensive) meters, suchas those made by Fluke, have an optional clamp thatplugs right into your existing meter, converting itto the inductive-pickup type. These are fine meters,but the adapters often cost more than the meter it-self. By the time you add up your total investment,you would be better off buying a separate meter witha built-in clamp. Keep it simple; to read big amps,get a meter designed to handle the task right out ofthe box.

In summary, for most basic circuit checks onyour boat, a meter with a 10- to 20-amp capabilitywill do the job. However, if you wish to check alter-nator output in amps, starter current, and anchor-windlass loads, you’ll need the higher-amperagecapabilities of some of the better meters. There aremany multimeters available, and the one you selectwill depend on your budget, your boat’s equipment,and the intensity of your desire to do it all.

The Multiple-Multimeter SolutionI have found that the best solution to this dilemma ofwhich multimeter to buy is to combine several rela-tively inexpensive instruments rather than to buy onemeter that does everything. A basic digital multime-ter with a 10- or 20-amp capability will be just finefor testing most of the lighting and small-motor cir-cuits on your boat. For measuring any circuits draw-ing over 20 amps, Snap-On makes an inexpensivepair of inductive-pickup analog amp gauges (Snap-On part number MT1009), which read to 100 ampsin DC and to 500 amps in AC. In this case the ana-log scale is fine because with high-amperage tests wedon’t need to measure tiny fractions of an amp; areading in whole amps is plenty. These gauges willserve your needs well for everything but shore-poweror AC generator work.

Figure 3-1 shows one of my inexpensive 20-amp multimeters and the MT1009 Snap-On gaugeset. This combination of instruments can bebought for under $100 and will measure currentup to 500 amps.

28


The ideal situation for general marine work wouldbe two meters in your toolbox: one medium-pricedgeneral-purpose meter with a diode-check featureand a 10- to 20-amp capacity, and one inductive-pickup meter with at least a 600-amp capacity. Mostworking marine electricians have several meters thatthey use regularly, and it’s not unusual for some gad-get hounds to own four or five different meters.

A Few Specific RecommendationsThere are a few inductive meters with which I ampersonally familiar and can recommend as goodchoices for your first meter.

Ancor 702070One excellent general-purpose meter is the latest Ancor-brand pocket meter (see figure 3-2, page 30)with built-in inductive pickup. This meter doesn’tquite reach my ideal of a 600-amp capability, but onmeasurements of up to 200 amps in both AC and DCit does a fine job. It also has the usual ability to mea-sure volts and resistance and the less-usual ability tomeasure frequency (we discuss frequency, or Hertz,in chapter 11). Frequency measurements are usefulfor checking the output of shore-power outlets,

generators, and inverters, to make sure they are run-ning properly.

The Ancor meter does not have a diode-testfunction, and in actual use I have found that it willnot effectively test some diodes commonly used in

29


� A Word about Inductive PickupsInduction is the phenomenon whereby an electrical current flowingthrough any material creates a magnetic field around the material. Forexample, a lightning bolt passing through the atmosphere can gener-ate a huge magnetic field around it, and every time Wile E. Coyote grabsthe wrong wire as he is trying to electrocute the Road Runner, it’s theinduction-induced magnetic field that makes his fur stand on end.Because of induction, any wire that has electrical current flowing throughit will have a magnetic field surrounding it, regardless of the insulationused and the strength of the current. The intensity of the magnetic fieldincreases in direct proportion to the current flowing through the wire.Thus, the higher the current, the stronger the magnetism.

Inductive-pickup meters measure this magnetic force and convertthe reading into amperes. Meters with an inductive pickup can save alot of time, and they are much easier and safer to use than those thatmeasure amperage with probes. Just clamp the meter around thewire from which you want to take a reading, and, if you have thething turned on and set properly, the meter does the rest.

Also, meters with an inductive pickup will have a small arrow em-bossed on the inside of the clamp jaws. This arrow should point to-ward the power source in the circuit, not toward the electrical load. (Ifyou get it backward, you’ll get a negative reading.) Finally, to ensurean accurate reading when using an inductive meter, it’s important tokeep the jaws as close as possible to 90 degrees in relation to theconductor you’re checking.

The inductive meters are a great choice for most of us, but they dohave their drawbacks. An inductive meter can measure the amperageon only a single wire at a time, so bundled wires or wires enclosed ininsulation can be difficult to measure on occasion. Also, on circuits draw-ing less than 1 amp of current, some inductive meters may not besensitive enough to get a reading. In this case a less-expensive con-ventional meter may be a better choice. This is a point worth checkingbefore spending several hundred dollars on a clamp-type meter if you’llbe working with many circuits with less than 1 amp of current. How-ever, most onboard electrical equipment will use 1 amp or more. Themost common exceptions are electronic equipment in standby modeand some small fluorescent lights.

Fig. 3-1. A 20-amp multimeter with Snap-On inductive me-ter set offers a fairly economical solution for measuring am-perage up to 500 amps. The combination can be purchasedfor under $100.

marine applications, such as those used in batteryisolators. It does work for testing most alternators,but it may not be adequate for many inboard or in-board-outboard starter-current tests. The Ancor(part number 702070) is available through majormarine retailers such as Defender Industries andWest Marine for about $300.

Fluke Model 336If you’re the type that simply has to have the best,Fluke Corporation makes what I consider to be someof the finest multimeters available anywhere. Thereare other fine meters, of course, but Fluke’s top-of-the-line Model 336 offers one additional feature thatwill be useful if your boat is equipped with extensiveAC circuitry such as a generator, inverter, or air-conditioning and refrigeration systems. This meterwill measure up to 600 amps DC and 600 amps AC,far beyond what most boaters need. It does not havea diode-test function, however, nor will it measureAC frequency.

Figure 3-3 shows a Fluke Model 336 true RMSclamp-type inductive meter. It’s available through allthe major marine supply houses in the United Statesfor about $275.

Both of these meters come with fairly easy-to-read instructions, but be warned that the meter com-panies in general assume that you know how toattach the meters to the circuit correctly for the mea-surement you’re making. Reading the sections thatfollow will assure that you do!

Using Your MultimeterThere are literally hundreds of checks and tests thatyou’ll be able to carry out with your new multime-ter. However, at least 90 percent of everything you’llever need to do will involve some form of the fol-lowing four basic procedures: voltage measurement,voltage drop, amperage measurement, and resistancemeasurement. These procedures are so importantthat we discuss each in detail. Measuring voltage isthe easiest, so let’s cover that one first.

Measuring VoltageTo test for voltage, first make sure that your meteris turned on and that the leads are inserted into thecorrect sockets (the leads that came with your newmeter probably have spike-like probes on the ends,

30


Fig. 3-3. Fluke Model 336 clamp-type meter. This is a trueRMS (root-mean-square) meter that can read up to 600 ACor DC amps. This is an excellent choice if you do a lot of ACwork. Its shortcoming is that its ohms scale is not as sensitiveas other meters I’ve used. This model sells for about $275.

Fig. 3-2. Ancor/Prova clamp-type meter. This unit retails foraround $300 and offers amperage reading capability up to200 amps and a frequency-checking function, useful forsome AC tests. Made by Prova, marketed in the UnitedStates by Ancor.

although a rare few might have alligator clips). Theblack lead goes into the socket that’s probablymarked “COM,” and the red one goes into the socketmarked “DCV” or something similar. If you do nothave a self-scaling meter, also double-check to makesure that your meter is set to the proper range (20volts for a 12-volt system). Now go to one of yourboat’s 12-volt batteries and touch the black probe tothe negative terminal and the red probe to the posi-tive terminal. You should be able to read the batteryvoltage on your meter’s digital readout. If your bat-

tery has a full charge, this reading will be between12.6 and 13.5 volts. A negative sign in front of thevoltage means that you have the probes connectedbackwards.

That’s all there is to a voltage check. Once youhave your meter set up properly, any time you touchthe red probe to a hot positive terminal or bare wireand the black probe to a negative terminal or wire (orto ground), your meter will tell you the voltage atthe point the red probe is touching. In other words,whenever your meter leads are connected to the cir-cuit in parallel, as is explained in chapter 1, withsome sort of load between them, you get a voltagereading.

Inexperienced meter users often make simple mis-takes and become puzzled when their new metershows no reading at all. This absence of a reading canbe dangerous because it can lead the novice to believethe circuit is turned off when it’s in fact still live or hot.

Figure 3-5 on page 32 illustrates a multimeterproperly connected to a 12-volt circuit to check for ad-equate voltage at a cabin light. The red meter lead isconnected to the positive terminal on the light, and theblack lead is connected to the negative connection.

Many beginners get confused when they try tocheck voltage at points throughout a circuit and can’tfigure out what to do with the black lead. This leadshould always be connected to the yellow (or blackon older boats) lead of the circuit you’re testing orto a good ground connection.

Figure 3-6 on page 33 shows this same circuitwith a meter hooked up in parallel to the switch ac-tivating the circuit. In effect, both meter leads areconnected to a positive feed with no load betweenthem. This hookup is incorrect and will not show avoltage reading under any circumstances.

Testing for Voltage DropVoltage drop, as we discovered in chapter 1, is thenatural and unavoidable loss in voltage as amperageworks to overcome resistance in a circuit. The drop isthe amount of source voltage loss caused by the in-herent resistance to electrical flow through the wiringin the circuit and any connections where wires andcircuit components are installed.

31


Fig. 3-4. Meter on a volts scale hooked in parallel across abattery. A fully charged battery would read between 12.6and 13.5 volts.

Virtually all circuits contain some resistance.Thus, there is always some voltage drop in every cir-cuit. This is true in AC circuits as well as in DC cir-cuits. However, because of the trade-off betweenvoltage and amperage (as voltage in a circuit goesup, the amperage required to do the same amountof work goes down), the drop in a 120-volt AC circuitis of little consequence. With low-voltage DC cir-cuits, however, voltage drop is a major concern andyou’ll need to know how to measure it.

So how much voltage drop is acceptable? Onceagain our friends at the ABYC offer some guidelines.Section E-11 of the Standards and Technical Infor-mation Reports talks about critical and noncriticalcircuits. Certain fixtures such as navigation lights,bilge pumps, and navigation equipment are requiredfor safety, and their efficient operation is critical.However, the brightness of a cabin light or the speedof a fan in the galley just isn’t that important. Thus,the standards allow only a 3 percent maximum volt-age drop for critical equipment and up to a maxi-mum of 10 percent voltage drop for noncritical

equipment. In a perfect world, and certainly in anyelectrical work you perform, it’s really best to shootfor 0 percent voltage drop as an ideal, but in the realworld some voltage drop will always be present, es-pecially in long wire runs.

There are several simple math problems that mayhelp you to get a feel for what the ABYC maximumvoltage drop figures mean.

Assume a 12-volt system. If a noncritical circuitis allowed a 10 percent maximum voltage drop, youneed to know what 10 percent of the system voltagefor your 12-volt circuit equals. In practice the actualnumbers will be slightly different. A fully charged 12-volt battery will have a voltage of between 12.6 and13.5 volts. The actual voltage would change the fol-lowing numbers slightly, but we will use the 12-voltfigure to simplify the math.

To find the allowable voltage drop, turn the per-centage into a decimal and multiply it by 12 (the sys-tem voltage in this example). The problem looks likethis: 0.10 x 12 = 1.2. The maximum allowable voltageloss would be 1.2 volts, so by subtracting 1.2 volts

from the original 12 volts, you endup with 10.8 volts as a minimum al-lowable voltage at any point in thecircuit. Applying this same math tothe 3 percent criteria, multiplying0.03 x 12 gives a maximum allowablevoltage drop of 0.36 volt, whichmeans that 11.64 volts would be theminimum allowed at the appliance.

Measuring Voltage Drop: Method 1So, now that you have an under-standing of the voltage drop that’s al-lowed in critical and noncriticalcircuits, how can you actually mea-sure it with your multimeter? Thereare two methods. The first method isprobably the simplest to understand,but it won’t always give the best re-sults when you’re trying to isolate theexact spot in the circuit that’s causinga problem.

32


Battery


CircuitProtector

Switch “On”

Fig. 3-5. Cabin light circuit diagram with a voltmeter connected to check volt-age going to one of the light fixtures.

Let’s assume you’re checking voltage drop at thelight fixture in the head. First make sure that all DCcircuits on board your boat except the one you’rechecking are turned off. Battery voltage must be keptas stable as possible for this test, and any circuits thatare turned on will drain the battery, if only slightly;this slight drain can alter your readings. Now checkthe voltage at your battery as described above. Ifyou’re checking voltage at the distribution panel,connect your meter with the red lead attached to thepositive bus at the back of the panel and the blacklead attached to the negative bus. Record your read-ing to at least two decimal places. Fractions of a voltcount here!

Next, go to the light socket and check the voltage.Again, the red test lead probe should be attached tothe positive side of the fixture and the black probe tothe negative side. You may have to disassemble thefixture to get access to the contacts for the light bulb.Put the red probe on one contact and the black tothe other and take a direct reading. Make sure the

circuit is on and the bulb is lit. If you’reworking with one of the more modern bay-onet bulb holders, connect the red probe tothe left-side bulb clamp and the black probeto the right side and take a direct reading.

If the reading you get is the same as thereading at the battery or distribution panel,great! No voltage drop is present. If thereading is lower than the source voltage, as it usually is, there is a voltage drop pre-sent. To measure it, subtract your readingfrom the source voltage. The difference be-tween the two readings is the voltage dropbetween the power source and the appliance.

Record the reading. To determine thepercentage of drop, subtract the light-socketreading from the source-voltage reading anddivide the result by the original source voltage.Shift your decimal point two places to the right,and you’ll have found the percentage of drop inthat particular circuit. Depending upon whichcategory the circuit falls into, the drop must beless than 3 percent or less than 10 percent. Ifyou get more than the 3 percent or 10 percentlimit, the circuit has excessive voltage drop,

which is probably caused by wiring that’s too small forthe length of the circuit or a loose or corroded connec-tion. You must now trace the exact fault.

The next voltage-drop test will isolate the dropbetween the positive conductor and the negative con-ductor of the circuit.

Figure 3-7 on page 34 shows voltage beingchecked at the back of a typical distribution panel.Figure 3-8 on page 34 shows the meter connectionsat your multimeter, and correct meter attachment ata variety of typical bulb holders.

Measuring Voltage Drop: Method 2The second method for checking voltage drop issometimes difficult for the beginner to understand.The meter will be connected in parallel, but youwon’t attach your lead probes to separate positive ornegative conductors. Instead, attach both yourprobes to the same conductor or between a terminalin the circuit and a terminal on the appliance you’re

33



CircuitProtector

Switch“On”

Battery

Fig. 3-6. Incorrect hookup of voltmeter across the switch of the samecabin light circuit. When the meter is connected in this manner, thesource voltage cannot be measured. The only reading you would gethere is the voltage drop through the switch.

testing. Sometimes you’ll be testing directly acrossswitches and relays or from one end of a wire to theother, even though I said earlier that you shouldn’tdo this.

Figures 3-9, 3-10, 3-11, and 3-12 illustrate thevarious meter-connection possibilities for this test.

Begin with the circuit you’re measuring turnedoff. The meter should be turned on, set to measure

DC voltage, and if your meter is not self-scaling itshould be set to the lowest voltage on the DC voltsscale (usually 2 volts). Once the meter is connected,turn the circuit on and take a reading on your me-ter. The reading is the voltage drop at that point inthe circuit. Record the reading.

Measure the voltage drop at each wire andconnection in the circuit, including the negativereturn, then add up the results. The total of allthese measurements must fall within either the 3percent or 10 percent limit. Any reading that’s alot higher than the others in the circuit indicates apoint in the circuit with excessive resistance orvoltage drop. Correct any problem by cleaning ortightening the connection, or by replacing theconnecting wire.

Measuring AmperageAs already discussed there are two methods used totest amperage. One method uses meter leads and re-quires the disconnection of the DC power lead forthe circuit you’re testing (I discuss AC in more de-tail in chapter 11); the other uses a clamp-type in-ductive meter.

Using Meter LeadsUnlike voltage checks, amperage checks with a basicmultimeter require that the meter be connected in

34


Fig. 3-8

Fig. 3-7. In checking source voltage at the back of a switchpanel, remember to always verify your power source first whentracing circuits.

Fig. 3-8. Meter lead connections on a meter and voltage checks for three light-socket types.

35


Solenoid

Starter Motor

CircuitProtector Switch “On”

BayonetLight

Fig. 3-9. Measuring the actual voltagedrop between the stud and the termi-nal. Remember, the circuit must beturned on to get any reading. The 0.2-V reading indicates either a looseor corroded connection that requiresrepair. Although less than 3% of 12V,0.2 V at any point in a circuit spellstrouble at that point.

Fig. 3-10. Checking the voltage drop atthe switch. Again, the circuit must be“on.” If the connections were clean andtight, the 0.2-V reading shown would in-dicate a fault (probably corrosion) insidethe switch.

Fig. 3-11. Checking the integrity of thestarter solenoid. Excessive voltage drophere necessitates removing the starterto replace the solenoid.

Fig. 3-12. The solid leads measure the voltage drop in the positive feed wire to the light. The dotted leads check the negativereturn. A high meter reading indicates undersized wiring.

Figs. 3-9, 3-10, 3-11, 3-12. Various hookups for checking voltage drop. In figure 3-12, the meter leads are shown as youwould trace through a circuit looking for voltage drop at various points in the circuit.

series with the circuit. (If you have probes on yourmeter leads, you’ll find this test much easier if yougo out and buy a set of leads with alligator clips onthe working end of the leads.) First make sure the cir-cuit is turned off and that your meter is turned onand set up properly. Double-check to make sure thatthe red lead is plugged into the socket for 10 or 20amps, if your meter has one. Now disconnect a wireat the point where you wish to measure the amperageand clip the black probe to the terminal that is closestto the battery. Clip the red probe to the remainingterminal. Figure 3-13 illustrates this basic hookup.

The meter’s leads must be in the appropriatesocket for the level of amperage being read. Meterswith the ability to measure both milliamps and wholeamps up to the 10- or 20-amp level may have sepa-rate sockets for the red test lead as shown in figure3-14. The black lead will remain in the “COM”socket. If your meter is self-scaling, you’ll have to se-lect between AC and DC only. If the meter is not self-scaling, you’ll have to select a scale appropriate foryour expected reading. Figure 3-15 shows some typ-ical current values for the equipment on your boat.

Using an Inductive PickupIf you have an inductive meter, it may have severalscales to select from. Generally these meters will havea high- and a low-amps scale in addition to the usualselection of AC or DC. As with the standard meter,simply select the scale for your expected readingbased on the chart in figure 3-15. Some inductivemeters require the DC amperage scale to be cali-brated before each use. In this case, with the meter setup and the jaws of the clamp closed, just rotate thecalibration knob until zero appears on the scale.

Now isolate a wire at the point in the circuitwhere you want to measure amperage. This might in-volve unbundling a bunch of wires, or in extremecases it might involve adding a short run of wire to acircuit. If you must add a piece of wire to get a placeto clamp your meter, make sure the wire is largeenough for the circuit and that the temporary termi-nals are tight; otherwise you might change the dy-namics of the circuit enough to get an inaccuratereading. Once you have a wire isolated, simply clamp

36


Battery

Load

Cabin Light

CircuitProtector

Switch “On”

Fig. 3-13. Basic ammeter series hookup. Remove the fuseand attach the meter leads as shown; all the circuit’s powersupply must then flow through the meter once the circuit isturned on. Here the meter measures a 2 A current draw bythe cabin light.

Fig. 3-14. A meter showing a 1- and 20-amp socket. The 1-amp socket would be used to measure milliamps.

the meter around the wire with the equipment on thecircuit turned on, make sure the meter is orientedproperly, and read the amperage off the scale.

Ammeter use will be illustrated in a variety oftests throughout this book, so if you’re still uncer-tain about how to use your meter, the photos anddiagrams that follow should set you straight.

Measuring Resistance and ContinuityAll circuits and the components within them havesome resistance to electrical flow. However, if anycurrent at all is flowing through a circuit, you have aclosed circuit and what is called continuity. When do-ing a continuity check, you won’t really care what theactual resistance might be. Any resistance readinglower than infinity will indicate continuity. You’llusually use a continuity check to look for an open orbroken circuit.

Suppose, for example, that light in the head wewere working on earlier were to suddenly stop work-ing. The first thing you would check is the conditionof the bulb. Then you would check to make sure thatthe switch was on and the circuit breaker or fuse wasin good order. Still no light? It’s time for a continu-ity check.

First set up your meter to read ohms. You’ll nowbe using it as an ohmmeter. The scale isn’t that im-portant, but it’s best to set non-self-scaling metersto the lowest scale. If your meter has a continuityalarm, touch the probes together and listen for thebeep. Also check for a zero reading on the face of themeter indicating zero ohms. If you don’t get a beepor if the meter doesn’t read zero, the internal batteryfor your meter is probably low and will need replac-ing. Next disconnect the wire for the light fixture atthe distribution panel and at the light itself and con-nect one probe to each end of the wire. It doesn’tmatter which probe goes on which end.

Like the amperage test above, the continuity testis usually much easier if you have a set of meter leadsthat use alligator clips in place of spike probes. It’salso unlikely that your leads are long enough toreach from the distribution panel to the light fix-ture so you’ll need a jumper wire. Any piece of wirethat is the correct size and length will do fine. Justadd an insulated alligator clip to each end, andyou’re in business.

Now clip one end of your jumper wire to the wireyou disconnected at the distribution panel and theother end to either meter lead. Clip the other meterlead to the wire you disconnected at the light fix-ture and listen for the beep. If you don’t hear a

37


Typical DC Amperage Draws for On-Board EquipmentEquipment Amperage Draw Load (range, depending on unit)

anchor light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1–3 Aanchor windlass . . . . . . . . . . . . . . . . . . . . . . . . .75–300 Aautopilot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1–30 Abilge blower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1–3 Abilge pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.5–5 Acabin fan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1–2 Acabin light (incandescent) . . . . . . . . . . . . . . . . . . . . .1–4 Afish-finder . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.1–1.0 Afluorescent light . . . . . . . . . . . . . . . . . . . . . . . . . .0.7–2 Afreshwater pump . . . . . . . . . . . . . . . . . . . . . . . . . . .4–5 Aknotmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.1–1.0 ALoran/GPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1–2 Amacerator pump . . . . . . . . . . . . . . . . . . . . . . . . .15–20 Amasthead light . . . . . . . . . . . . . . . . . . . . . . . . . . . .1–2 Aradar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4–8 Arefrigeration (DC) . . . . . . . . . . . . . . . . . . . . . . . . . .5–8 Arunning lights . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3–6 ASSB radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1–2 A

(transmit 25–30 A)stereo/tape deck/CD . . . . . . . . . . . . . . . . . . . . . . .1–2 AVHF radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.7–1.5 A

(transmit 5.0–6.0 A)washdown pump . . . . . . . . . . . . . . . . . . . . . . . . .2.5–5 Awiper motor (each) . . . . . . . . . . . . . . . . . . . . . . . .1.5–5 A

Fig. 3-15. A table showing typical current draws for power-boat equipment. Remember that these values are approxi-mate and your equipment may vary from these values.Always confirm the draw for your own equipment.

beep, you either have the meter connected improp-erly or you don’t have continuity. If you don’t havea continuity alarm, check for a reading on the me-ter. Any reading but OL (overload) is fine. Zeromeans no resistance at all. OL means infinite resis-tance and a break in the circuit.

A common mistake made by beginners (and morethan a few of us pros) is to pinch the probes of themeter leads onto the ends of the wire with bare fin-gers. If you try this and there is a lack of continuity inthe wire, the current from the meter can take a de-tour through your body and your meter will beep andshow continuity when none exists. Any time you’reusing your meter it’s best not to touch the probes,but when you’re checking continuity or resistance it’s

critical to keep your hands away from them.Whenever you’re using the ohms scale on your

meter, the wiring you’re working with must not belive. The switch for the circuit must be off. The ohmsscale and the diode-check function use a tiny amountof calibrated current from the meter’s internal bat-tery. Even a small amount of external current can dis-tort your reading or even damage the meter. Failureto turn off the circuit will trip your meter’s internalfuse or, in the case of some inexpensive meters with-out internal protection, you’ll burn the meter out.

Figure 3-16 shows an ohmmeter battery test be-ing performed and what your meter’s screen shouldindicate.

What Do the Numbers

on My Ohmmeter Tell Me?Proper interpretation of your multimeter’s ohmreadings is important; otherwise, misdiagnosis ofproblems can occur. Unlike the direct readings onthe volts and amps scales, resistance values are a bitmore cryptic for the newcomer to electrical testing.

If you’re using a digital meter, the letters OL onyour screen stand for overload, which replaces thesymbol for infinity familiar to analog instrumentusers and is shown in figure 3-17. OL means that theresistance being read by the meter is higher than itsability to read it and usually indicates a break in thecircuit, or an open circuit. If your meter is reading astring of zeros, perfect continuity is indicated with noperceptible resistance. Any numbers shown on yourmeter (including zeros) show the resistance in ohmsand indicate a complete circuit.

38


Fig. 3-16. Checking the ohmmeter battery by touching theleads together. Some meters also have a “BAT” indicator onthe face that indicates when power from the unit’s internalbattery is too low.

Fig. 3-17. OL (overload) shown on the face of a digital mul-timeter.

Specific resistance is not too important for gen-eral circuit checks. Specifications are never given, andgeneral assumptions really can’t be made consideringthe variety of equipment available. For example, ifyou checked for continuity through a circuit for yourstern light and you got a resistance reading, it wouldindicate that all is well through the circuit. The resis-tance you’re reading is in the light bulb filament.(Typically, bulbs of this type will show several hun-dred ohms of resistance.) But suppose you check thesame circuit and you see an OL reading on your me-ter. This indicates an open circuit, and most probablythe bulb is blown and needs replacement.

An ohm reading near zero would indicate a shortcircuit between the positive conductor and ground. Ifthis circuit has been blowing fuses or tripping the cir-cuit breaker, you’ll know you’re on to something—the first step in tracing a short circuit!

Figures 3-18, 3-19, and 3-20 show the three possi-ble meter readings, and what is happening in the cir-cuit to give these readings.

On some components, like ignition coils andspark-plug wires, resistance values are given in work-shop manuals so you have a specification to workwith. In these cases, use your ohmmeter to test forfaults within the components by matching readingsto the specifications. On non-self-scaling meters,you’ll have to select the appropriate ohms scales.

Even self-scaling (auto-ranging) models can be abit confusing. Some meters give a direct reading withthe decimal point placed exactly as it should be, butothers have a high or low scale and require some mi-nor interpretation to place the decimal. Read yourmultimeter’s instructions carefully to be certain youhave a clear understanding of how this scaling workson your meter.

Actual tests on ignition components as well asother ohmmeter tests where specific resistance valuesare important will be illustrated in chapter 7.

So, as we close out chapter 3, remember the tipsgiven here and carefully select the best multimeteryou can afford. Your meter is a long-term invest-ment, and, unlike today’s computer, it will never beobsolete. Volts, amps, and ohms haven’t changed onebit in over a century! However, some of the latest

developments in this area utilize software and PC up-loads from some of the newest high-end meters fortracking voltage, amperage, and resistance changesover time. Rest assured, I’ll be adding this capabilityto my arsenal of electrical test equipment in the not-too-distant future!

39


Figs. 3-18, 3-19, 3-20. Sequence diagram showing a circuitwith continuity and some resistance on a meter, the samecircuit showing a break or open and the “OL” reading on themeter, and the same circuit showing a short and a typicalmeter reading.

Fig. 3-20. Continuity and possible short circuit.

Fig. 3-19. Open circuit and no continuity.

Fig. 3-18. Continuity.

Wire and Circuit Protection Standardsand Repair Procedures

40

Order Out of ChaosIf you were to study the development of the Ameri-can pleasure-boating industry from the turn of thetwentieth century to the early 1970s, you would no-tice a curious phenomenon. While other developingindustries gradually evolved a more-or-less uniformset of standards that dictated the minimum safetyand performance parameters for their products, therecreational marine industry had none. For manyindustries, such as automobiles, aircraft, food, andhealth, the government dictated the standards. Inother less critical industries, and particularly inrecreational industries, the standards were imposedby the industry itself or by the marketplace.

Take golf, for example, which, overlooking thedifferences in accident rates, is remarkably similardemographically and statistically to pleasure boat-ing. Golfing gradually developed a set of rules andstandards for course construction and equipmentdesign that industries involved in the sport violatedat their peril: If a golf course is not laid out just right,nobody will play on it, and if a golf club isn’t builtjust so, no one will buy it.

Remarkably, no such basic standards ever devel-oped for the people and companies that built plea-sure boats. It’s true that industry leaders likeChris-Craft, Owens, Penn Yan, and many othersbuilt quality products to their own standards thatwere an excellent value for their customers. How-ever, some builders produced shamefully shoddyboats that were not only a poor value but dangerousas well. One New England manufacturer of openfishing boats, for example, built hundreds of boatswith particleboard decks and transoms that liter-ally melted once water penetrated the paint job. An-other company, in California, became famous forbuilding boats with fiberglass hulls that were so thinthat you could read a newspaper through them.

The U.S. Coast Guard has a long list of safety reg-ulations that apply to recreational boating, but fewof these standards applied to the construction of theboat. That bassboat with the particleboard decks, forexample, had a legal limit on the number of peopleit could carry and the horsepower of the outboardit could use, but not a word was ever said about theintegrity of the basic construction.

Finally, out of frustration with fly-by-night buildersand a growing accident and fatality rate that was giv-ing recreational boating an increasingly tarnished im-age, the industry banded together. Organizations likethe National Marine Manufacturers Association(NMMA) and the American Boat & Yacht Council(ABYC—for contact information see the sidebar onpage x)—were formed with the stated purpose ofbringing order out of chaos by establishing a bindingset of minimum standards for the construction ofpleasure boats. One of the remarkable results of theformation of organizations like these has been a steadydecrease in the number of fatal boating accidents.

ABYC Standards and RecommendationsThe ABYC standards and recommendations towhich I refer throughout this book do not just ap-ply to boatbuilders, however. They apply to you andto me and to everyone who works on boats. In fact,recent certification programs for marine techni-cians initiated by the ABYC drive home the pointthat the standards are as useful for repairing andmodifying boats in the field as they are for buildingboats in the factories. These standards are an in-valuable tool for weekend boaters who decide tomake their own repairs and perform some of theirown installations. Much of this chapter addressesthe points you should consider when selecting wire,

Chapter 4


circuit breakers, and fuses. We will even discuss a fewbasic electrical repairs you can make on your boat.

If you own a boat that’s more than a few years old,it may not comply with all of the standards outlinedin the ABYC’s Recommended Standards and TechnicalInformation Reports. This is not a cause for immedi-ate concern. These standards have evolved over theyears and have been revised as new materials andtechnology became available. The tables, charts, andrecommendations in this chapter and in the rest ofthis book reflect the recommendations of the ABYCat the time this book was written. Wire types and cir-cuit-protection ratings are not likely to change in theforeseeable future. On the other hand, there couldbe breakthroughs in insulation technology as newerand better materials are developed, and a technolog-ical advance might create a new circuit breaker thatwill be better than the ones we use today. If either ofthese events should transpire, rest assured that theABYC will take a close look and make appropriaterecommendations based on what they see.

Basic WiringThe ABYC electrical standards go into great detailon the minimum criteria for both DC and AC cir-cuits used on boats. Basic considerations include thelength of the wire, nominal voltage, amperage, rout-ing of the wire, insulation temperature rating, andthe chemical environment to which the insulation islikely to be exposed. One additional consideration isthe conductive material used in the wire.

Wire TypesElectrical wire comes in a variety of types and con-ductor materials, but by far the most common con-ductors are made of copper. Aluminum is used insome automotive applications, but aluminum con-ductors of any type, including terminal strips andstuds, are strictly prohibited in the ABYC electricalstandards. The soft aluminum used in wiring cor-rodes easily (unlike the hard aluminum used in boathulls), and it can become brittle and break when sub-jected to the constant vibration and flexing of a typi-cal boat underway. It also isn’t as good a conductor

as copper, and the added resistance means that it getshotter quicker than copper. Don’t ever use alu-minum wire on your boat, and if you find any al-ready installed, immediately remove it and replace itwith copper wire.

In addition, solid wire, especially the solid-copperRomex that’s used in house wiring, is never accept-able on boats. This precludes the use of many wiringtypes found in hardware stores or in home-supplyhouses. Solid-copper residential wiring breaks easilyunder vibration, and it was never intended to with-stand the exposure to moisture or oil and gas fumesfound on today’s boats.

According to the ABYC specifications, the onlyacceptable material that may be used for boat wiringis stranded copper. Although not specifically men-tioned in the standards, good-quality boat cable to-day is often tinned as well. This means that everystrand of copper in the wire is coated with a thin layerof tin (solder, actually) that impedes the formation ofcorrosion. Copper doesn’t corrode in the same wayas such materials as aluminum and steel, but formsa thin layer of oxidation that’s highly resistant toelectricity. The tinning slows and reduces the forma-tion of this oxide layer and greatly reduces the inci-dence of problems caused by corroded wires. It’s alsomuch easier to solder than untinned wire.

Tinned copper wire will pay off in the long run.Initially it may seem a bit expensive compared tostranded copper without tinning, but on a boat,where corrosion is a constant battle, the tinned wirewill hold up far longer than would untinned wire.The tinning does a great job of resisting corrosion atterminals as well as preventing oxidation from mi-grating up the wire under the insulation, a commonproblem with untinned wire.

Stranded copper wire is available in several types.The chart in figure 4-1 on page 42 is taken from sec-tion E-11 of the ABYC’s Recommended Standards andPractices and illustrates several additional points. No-tice that the American Wire Gauge (AWG) standardis used to designate wire size. You may encounterwires on your boat that carry the Society of Auto-motive Engineers (SAE) designation. Quality ma-rine-grade wire with an AWG-size is often larger in

41

Wire and Circuit Protection Standards and Repair Procedures

42


diameter than the equivalent SAE designation. Stickto AWG-rated wires, prefereably those marked “boatcable” on the insulation.

As the wire-gauge numbers get smaller, the wiregets progressively bigger in diameter, and the mini-mum circular cross-sectional area of the wire, indi-cated by circular mils (CM), gets larger. Next, thechart shows the minimum number of strands forboth Type 2 and Type 3 wire. The finer the strands,the more strands there are in a wire of a given sizeand the more flexible the wire will be. It’s easy toidentify the two wire types, because Type 3 wire has alot more strands than Type 2. For example, an AWG

10-gauge Type 2 wire will con-tain 19 strands of wire, whereasan AWG 10-gauge Type 3 wirewill have 105 strands. Type 3wire will also have a slightlylower resistance for a givengauge than a Type 2 wire.

Wire SizeOnce you have determinedthe type of wire to use on yourproject (and in nearly all casesthis will be Type 3 tinned cop-per wire), you must decidewhich size. Important consid-erations here are the length ofthe wire, the voltage (usually12 volts, but if your boat isover 35 feet long you mighthave a 24-volt system), andthe amperage the circuit is ex-pected to carry (sometimescalled ampacity). This infor-mation is usually supplied bymanufacturers of the equipmentyou intend to install on the cir-cuit. If it isn’t contained in theinstruction manual or printed onthe side of the equipment itself,you may have to perform thefollowing test to determine whatthese values are.

To test for amperage, connect the equipment youwant to test to your boat’s battery (or any 12-voltbattery) with a set of automotive jumper cables.Hook the positive lead to the battery first and thenegative lead next. Be careful not to let the clampsat the other end of the cables touch and arc. Next, setup your multimeter to measure DC amps.

When you’re uncertain of the amount of current apiece of equipment will require, it’s best to performthis check with your meter’s 10- or 20-amp setup.An over reading on the wrong scale (with the meter’sleads in the incorrect sockets) will blow the meter’s

Fig. 4-1. Table XII from the ABYC electrical standards, section E-11, comparing wiretypes and stranding. (© ABYC)

43


internal fuse. Make sure that the jumper leads areconnected to the DC positive and negative terminalson the piece of equipment in question. Clip the leadsin series with the load and take the amperage read-ing once the equipment is running. With an induc-tive clamp meter, simply get the equipment running,clamp onto either of the leads of the jumper cables,and take a reading.

Figure 4-2 shows the hookup for making this ba-sic test. For a look at the typical amperage for com-mon items of equipment you might find on your

boat, refer to figure 3-15 on page 37.Once you have established the amperage for the

equipment you’re testing, selecting the correct size ofwire to use is simply a matter of working the numbersfound in figures 4-3 and 4-4 on pages 44 and 45.

Let’s try out figure 4-3. You’ve decided thatyou’re dealing with a critical circuit and will use the 3percent maximum voltage drop value. Yours is a 12-volt boat, and you know that the pump in questiondraws 5 amps and that 20 feet of wire separates itfrom the panel board supplying the pump. A two-

way run would mean a total conductorlength of 40 feet. Find the 40-foot columnon the chart and correlate it with the 5-amp row in the 12-volt section. Youshould find a 10-gauge wire size recom-mendation.

Keep in mind that these two charts are de-signed for sizing wires based on the ABYCacceptable voltage drops described earlier.Don’t confuse the 3 percent and 10 percentspecifications. And most important, re-member that the length of the wire is the to-tal of the positive and negative sides of thecircuit. For example, if a component is 12feet from your distribution panel, the lengthof the run will be 24 feet. The column thatmost closely matches that on either of thesetables is labeled 25 feet. When a numberfalls between any two values, always roundup to the next highest number.

Wire InsulationQuality wire has a rather lengthy storywritten right on the insulation. The writ-ing on the wire can help you decide thewire’s suitability for certain applications:the maximum voltage for the wire and in-sulation; resistance of the insulation to oil,moisture, and fuels; and temperature rat-ings of the insulation; are all explained incryptic notation. Again, our friends at theABYC come

(continued on page 46)

Fig. 4-2. Battery jumper cables being used to determine amperage drawfor a new electrical installation. In this case, I’m checking the actual drawfor a new bilge blower.


Fig. 4-3. The ABYC’s Table X from section E-11, showing conductor sizes for a 3 percent drop in voltage. (© ABYC)

44

45


Fig. 4-4. Table XI from section E-11, showing conductor sizes for a 10 percent drop in voltage. (© ABYC)

46


(continued from page 43) through with severaltables to help decipher these secret codes. FromABYC section E-11 we see temperature-rating codesfor flexible cords in figure 4-5, and insulation char-acteristics and temperature ratings for typical wiringconductors in figure 4-6.

Another table, shown in figure 4-7 on page 48,shows the allowable amperage for various sizes ofwires used inside and outside engine-room spaces.Notice that the amperage decreases inside enginerooms where expected temperatures are greater thanoutside temperatures. Use this table to determinethe size of conductors for low-voltage DC systemsonly; AC wiring uses different criteria. The infor-mation on this chart must be compared to the infor-mation in the charts shown in figures 4-3 and 4-4.Always use the largest wire gauge indicated by thetwo charts for a given amperage based on the lengthof the wire run.

All wire used in DC circuitry should have a mini-mum rating of 50 volts stamped on the insulation.Most quality wire will have the AWG gauge embossedon the insulation as well. In general, wire sold as marine grade at the major supply houses will have a105°C rating for the insulation, but it pays to check.

Fuses and Circuit BreakersDepending upon when your boat was built and whobuilt it, you may have any combination of circuitbreakers or fuses of different types used as circuit-protection devices. All such devices used on pleasureboats work on one of three basic principles, two ofwhich depend on heat generated by resistance and athird that works on current-induced magnetism.Since fuses are easier than circuit breakers to under-stand, let’s take them first.

Fig. 4-5. Table VIII from section E-11, showing insulation markings and temperature ratings for insulation on flexible cordsas used on board. (© ABYC)

SO, SOW

ST, STW

SJT, SJTW

SJTO,SJTOW

STO, STOW,SEO, SEOW

SJO, SJOW

47


FusesIf you were ever foolish enough to connect the posi-tive and negative terminals of any 12-volt batterywith a length of wire with no intervening load to slowthe flow of electrons, the wire would immediately be-come red-hot and melt. This is how an unfused shortcircuit can quickly destroy a boat, and it’s how a fuseworks. If you interpose a short piece of smaller-gaugewire into this ultrasimple circuit, the smaller wire willself-destruct and stop the flow of electrons beforethe heat builds up enough to damage the larger wire.

You have, in effect, built yourself a fuse in the form ofthe smaller wire.

You might recall that in chapter 1 I noted that aby-product of resistance is heat. Well, a fuse is de-signed with an element that will carry a certainamount of current and then heat up to a point whereit melts, opening the circuit it’s designed to protect.The trick is to select a fuse that will allow sufficientamperage to flow freely through the circuit to runall the equipment on the circuit but will self-destructjust before the current reaches the point where it can

Fig. 4-6. Table IX from section E-11, showing insulation markings for typical wiring conductors found on board (exclusive offlexible cables). (© ABYC)

NOTE: Some of the listed types are not commonly available in stranded construction for sizessmaller than 8 AWG.

THW

TW

HWN

XHHW

MTW

AWM

UL 1426

damage anything. Fuses are simple devices, but toavoid problems with them there are some importantthings you should know.

Fuse Types and RatingsPopular fuse types shown in figure 4-8 include thecylindrical glass bus-type fuse designated as AGC, thenewer and increasingly popular blade-type fuse des-ignated as ATO, and a heavy-duty slow-blow fusedesignated MDL, or type T. There are many fuse des-ignations other than AGC, ATO, and MDL, but these

three are the most common and will do for ourpurposes.

The most important specification to look forwhen selecting a fuse is the amperage. When selectinga fuse for a circuit, base the size of the fuse on the cur-rent-carrying capability of the smallest wire in the cir-cuit. For example, if you select a 14-gauge AWG wireto get power from your distribution panel to a newdepth-sounder but the leads built into the sounderare only 16 AWG, the fuse must be rated for the 16AWG leads, even if they are only a few inches long.

48


Fig. 4-7. Table IV from section E-11, showing the allowable amperage of conductors for DC systems under 50 volts. (© ABYC)

NOTE: Cross reference with voltage drop tables in figures 4-3 and 4-4.

AGC and MDL FusesAGC fuses (often generically called bus fuses) are thepopular 1.25-inch glass-barrel fuses with tinned-cop-per end caps that have been around since the begin-ning of time. They are by far the most common typeof fuse used to protect individual pieces of equip-ment and circuits on boats today, and are the typemost often supplied with a piece of equipment whenyou buy it. Many bilge pumps, just to name one item,will have an AGC fuse in an in-line fuse holder wiredright into the positive lead of the pump. At least onemanufacturer (PAR) voids the warranty on thepump if this fuse is tampered with.

As you examine an AGC fuse, you may noticethat it has a voltage rating embossed on the metalend cap. Usually this will be a fairly high number like250 volts. Since you’re using these fuses for DC cir-cuits, this rating is completely irrelevant and can bedisregarded. If you blow a 10-volt fuse, for example,it’s perfectly OK to replace it with a 250-volt fuse, orvice versa. However, you would never replace a 10-amp fuse with anything other than another 10-ampfuse. We aren’t quite done yet, though. Some mo-tors and inverters require what is called a slow-blowfuse.

Motors and certain other devices require as muchas five or six times more amperage to get started asthey will use when they are up and running. Inverters

that supply AC loads to motorized equipment likeelectric drills will experience a surge of current when-ever the AC motor starts up because AC output isproportional to DC input. Obviously, if you tried toprotect any of these circuits with a regular AGC fuse,you would stay pretty busy changing fuses. A slow-blow (MDL) fuse allows a substantial amount of ex-tra current to flow for a specified length of timebefore it blows and opens the circuit, and is just thething for this situation.

Never make assumptions about the amperage ofan AGC or MDL fuse based on a visual inspectionof the element. Manufacturers use different materi-als for these elements with varying sizes and current-handling capabilities. Two fuses with elements thatappear to be the same size could have entirely differ-ent ratings. You need to read the amperage specifi-cation embossed into the end caps of the fuse itselfto be sure.

ATO FusesAn increasingly popular fuse being used by many ofthe large production boatbuilders is the ATO type,commonly referred to as a blade-type fuse. ATOfuses work in exactly the same way as the barrel-type AGC fuses mentioned above (the heat fromexcessive amperage melts the element and opensthe circuit), but they offer several advantages overAGC fuses. They are color coded, for one thing,and the colors match the amperage ratings, asshown in the table in figure 4-9 on page 50. WithAGC fuses you must remove the fuse to read theamperage; however, ATO fuses have the amperageembossed on the end of the fuse where it’s alwaysvisible, even when the fuse is installed. ATO fuseshave transparent plastic cases that allow you to seethe entire element, so there is never a questionabout whether it’s burned out or not. ATO fusesare also slightly easier to remove and replace thanare AGC fuses.

A disadvantage to ATO fuses is that many of themuse aluminum elements and blades. Using these fusesflies in the face of the ABYC directive for not usingaluminum wiring or connections on boats. I haveseen aluminum ATO fuses literally rot from corro-sion when they were exposed to salt spray. Always use

49


ATO Fuse

Bus Fuse

Fig. 4-8. Bus-type glass fuse, slow-blow cylindrical fuse,ATO blade-type fuse.

ATO in-line-blade fuse holders with rubber covers asshown in figure 4-10.

If you find any aluminum fuses or fuse holdersof any type on your boat, you should immediately re-

move them and replace them with tinned copper orbrass fuses and holders. If there is a question of whatmaterial an ATC fuse is made from, simply scrapeone of the fuse blades with your pocketknife. Alu-minum easily flakes away and reveals a shiny silvercoloration right through the blade. Tinned copperor brass will show a yellow or pink coloration as thetin coating gets scraped away.

Circuit BreakersFuses are an inexpensive and effective way to protectmost circuits from too much amperage, and they arepractically fool-proof if you pay attention and matchthe fuse to the circuit you want to protect. They dohave several important disadvantages, though. Forone thing, once they blow they are useless and mustbe replaced. This isn’t an economic problem becauseboth AGC and ATO fuses cost only a few centsapiece, but it can be a nuisance if you blow a fuse andfind that you don’t have a replacement. If this shouldhappen with a critical piece of navigation equipmentwhen you’re caught offshore in a storm, it could evenbe dangerous. Another danger is that many of usfaced with not having the correct size of replacementfuse will be tempted to use a fuse of a higher amper-age or, even worse, to jump the holder with a piece ofwire. (Actually, a chewing-gum wrapper is the fusejumper’s tool of choice.)

Another, less dangerous drawback to fuses is thatthey tend to be awkward to remove so that deacti-vating a circuit is sometimes inconvenient. This is es-pecially true when the boatbuilder has located thefuse holder in the back of some obscure locker, asoften happens. Here again, those among us who areeasily led astray might be tempted to work on a cir-cuit while it’s live instead of taking the trouble of re-moving the fuse. The answer to all these problems isto have a reusable fuse that incorporates a switch sothe circuit can be easily shut down, and this is justwhat a circuit breaker does.

Circuit breakers are available in only a limitedrange of sizes, the most common being 5, 10, 15, 20,25, 30, 40, and 50 amps. AGC, MDL, and ATO fuses,however, are available in increments of 1-amp, andeven fractions of an amp. This means that nearly all

50


ATO Fuses, Color and Amperage RatingAmp Rating . . . . . . . . . . . . . . . . . . . . . . . .Color

1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Black2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Gray3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Violet4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Pink5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Tan71⁄2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Brown

10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Red11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Blue12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Yellow13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Clear14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Green15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Orange

Fig. 4-9. ATO fuses, color versus amperage rating.

Fig. 4-10. In-line-blade fuse holder with rubber waterproofcap attached.

circuits on a boat need a combination of circuitbreakers and fuses. In most cases a circuit breaker willbe used to protect the circuit, and fuses will be used toprotect each piece of equipment on the circuit. A typ-ical lighting circuit, for example, might have five sep-arate 25-watt light fixtures wired in parallel, with a15-amp circuit breaker protecting the circuit and aseparate 3-amp fuse protecting each of the five lights.If a problem were to develop causing a current surgeat any one of the light fixtures, the fuse for that fixturewould blow, leaving the others still working. A deadshort in the main circuit, however, would trip the cir-cuit breaker and extinguish all the lights.

Ampere-Interrupting CapacityThe amperage rating of a circuit breaker is calculatedas a percentage of the current-carrying capability ofthe smallest wire in the circuit. There is an additionalrating, known as the ampere-interrupting capacity(AIC), that is a peak rating taking extreme situationssuch as catastrophic short-circuits and other surgesinto account. As a user, you need not worry aboutthe AIC rating, as all the reputable producers of ma-rine circuit breakers take these values into account.

Trip-Free BreakersABYC specifications state that all circuit breakersused in pleasure craft be of the trip-free type, definedas “a resettable overcurrent-protection device, de-signed so that the means of resetting cannot over-ride the overcurrent protection mechanism.” This isan elaborate way of saying that they don’t want youto be able to override the breaker by holding it closedonce it has tripped. With trip-free breakers, the prob-lem that caused the breaker to trip in the first placemust be located and repaired before the circuit canbe reactivated.

Types of Circuit BreakersThere are two kinds of circuit breakers commonlyused on today’s boats. Bimetallic breakers sense re-sistance-generated heat, and magnetic breakers sensethe magnetism induced by current flow. Let’s lookat them one at a time.

Bimetallic Circuit BreakersBimetallic circuit breakers use two dissimilar metals,such as copper and stainless steel, fused together intoa thin strip. In a normal state this metal strip con-nects the circuit inside the breaker. As current flowsthrough the breaker, heat is generated, and since thetwo metals have different rates of thermal expansion,one metal expands more than the other, bending thestrip. When the bending reaches a preselected criticalpoint, the contacts inside the breaker separate andopen the circuit.

Magnetic Circuit BreakersWe already know, from our reading in chapter 3, thatany conductor with current flowing through it willbe surrounded by a magnetic field. Our second typeof circuit breaker senses this magnetism, and whenthe magnetism reaches a critical magnitude, the cir-cuit breaker trips and opens the circuit.

Either of these two types of circuit breaker worksjust fine in most marine circuit-breaker panels, andit’s perfectly OK to mix them. In fact, since they bothfunction in exactly the same manner with no signifi-cant external differences, it isn’t important that youknow which type you have. Just be certain that what-ever breaker you select is designed for marine use,and you’ll be all set.

Removing Circuit BreakersA big problem with many of the circuit breakers I’veseen lately is in their labeling. Circuit breakers essen-tially all look alike, and the only way to be certain oftheir ratings is to read the label affixed to them. Theproblem is, some of these labels are located on the sideof the breaker, requiring removal of the breaker fromthe switch panel to be certain of the amperage rating.These labels are typically glued-on paper labels that af-ter a few years in the marine environment dry up andfall off or become very hard if not impossible to read.

Fortunately, removing a circuit breaker from itsholder is a straightforward procedure. First be sure toturn off the master switch feeding the distributionpanel to avoid arcing any wiring as you remove thebreaker. Next, back out the one or two screws adja-cent to the switch handle on the face of the panel and

51


slide the breaker out from the back. Figure 4-11shows the screws on the face of the panel holdingthe breaker in place, and figure 4-12 shows thebreaker, with the specification label showing theunit’s ratings, removed.

Ignition ProtectionElectrical ignition-protection regulations for gaso-line-powered recreational watercraft go beyond theABYC’s voluntary standards and are enforced by theUnited States Coast Guard. ABYC section E-11 defines ignition protection in these official words:“Ignition Protection—The design and construc-tion of a device such that under design operatingconditions

� it will not ignite a flammable hydrocarbon mixture

surrounding the device when an ignition source

causes an internal explosion, or

� it is incapable of releasing sufficient electrical or

thermal energy to ignite a hydrocarbon mixture,

or

� the source of ignition is hermetically sealed.”

What this means to me and you is that on gasoline-powered craft we can’t have electrical stuffbelow decks that will ignite fuel fumes and blow upour boats. To this end, two important classificationsneed to be considered: the Society of Automotive En-gineers (SAE) designation J 1171 and the Underwrit-ers Laboratory (UL) designation UL 1500. Thesespecifications state that the equipment to which theyapply has been tested and approved for operation inexplosive atmospheres. Approved equipment willhave the fact that it meets the ignition-protectionstandards written right on the specification plate. Ig-nition-protected circuit breakers will have the state-ment “ign. protected” on the case. Figure 4-13 showsthis labeling on the back of a circuit breaker. Makesure the components you use meet these standards.

These ignition-protection regulations apply to allareas below decks except for accommodation spacesand well-ventilated areas specified in section A-1.6

52


Fig. 4-11. Screws mounting a circuit breaker in place on atypical panelboard. Turn counterclockwise to remove. Also,make sure the main switch to the panel is turned off beforemoving breakers out of place.

Fig. 4-12. Circuit breaker removed, showing paper label. Af-ter a few years, you can count on these labels being unread-able and even coming unglued and disappearing altogether.

of the ABYC standards. There are exceptions to therules for diesel-fueled boats, but on countlessoccasions I have seen jerricans of gasoline storedin diesel engine rooms. This circumvents the in-tent of the regulations, and one foolish move bythe owner of these boats could cause a disaster. Animproperly stored LPG (liquid propane gas) tankis also a time bomb.

Testing Fuses and Circuit BreakersOne of the very first things you should check when acircuit of any type becomes inoperative is the condi-tion of the fuses and circuit breakers, so it’s impor-tant that you know how to verify that they areworking properly. You might be saying to yourself,“Hey, my boat has all glass bus-type fuses. All I needto do is look at a fuse and I can tell if it’s blown ornot.” This is not necessarily true. Often these AGC

fuses will fail under the end caps where the break inthe element is out of sight. When some brands of cir-cuit breakers trip, the reset lever remains in the “on”position and they give no visual clues as to their con-dition; this is especially true of the trip-free breakersrequired on boats. Fortunately it’s easy to test circuitbreakers and fuses using your multimeter.

Testing FusesFirst, be sure the boat’s battery master switch isturned on. Now set your meter to the appropriateDC voltage and attach the black probe to the DC neg-ative bus on the back of your distribution panel orto any good ground. Touch the probe of your redlead to the positive side of the fuse holder and take areading of your battery voltage. If you don’t get areading, you have a problem in the feed to the fusefrom the positive bus bar. If you do get a reading ofbattery voltage, move your red probe to the terminalat the other end of the fuse and see if you get the samereading on your meter. If the reading is the same asthe battery voltage, the fuse is working. If you don’tget a reading, the fuse is blown and needs to be re-placed. If you get a reading but it’s lower than thebattery voltage, you have a voltage drop that’s proba-bly caused by a corroded fuse holder. Remove thefuse and clean it and the holder. Replace the fuse andmeasure again. The reading should be the same onboth sides of the fuse.

Testing Circuit BreakersTo check for electrical continuity through a circuitbreaker, first switch the breaker on and make surethat the terminals are clean and tight. With one me-ter lead attached to a known good ground, take areading on the positive side of the breaker the sameway you did for a fuse. If you get an identical read-ing at the adjacent terminal on the breaker, thebreaker is working fine and any problems you may behaving with the circuit have nothing to do with thecircuit protection. If you do not get an identical read-ing on both sides of the breaker, it’s faulty and willrequire replacement. Make sure to match the ratingof the new breaker with the old one. Figures 4-14aand 4-14b on page 54 show this test.

53


Fig. 4-13. “Ign. protected” label on a protected breaker. Thisis the only breaker type that should be used in an engineroom or compartment where CNG or LPG are stored.

Levels of Circuit ProtectionFuses and circuit breakers are intendedto protect the wiring and componentsin the circuit from damage due to ex-cess current flowing through any partof the circuit at any time. The ABYChas come up with standards designedto provide the most practical solutionsto the problem of protecting circuits.However, even the most experiencedelectricians and boatbuilders some-times have trouble interpreting thesestandards.

The 100–150 Percent RuleThe 100–150 percent rule contains thestandards for the rating of fuses andcircuit breakers for different types ofcircuits under differing circumstances.Some circuits must be protected with afuse or circuit breaker that’s no morethan 100 percent of the total amper-age-handling limits of all the compo-nents on a circuit, and other circuitsmay have a fuse or circuit breakerrated as high as 150 percent of the totalamperage. One such division of stan-dards is between motor circuits andnonmotor circuits.

Motor CircuitsMotor circuits fall into a unique cate-gory. Starter-motor circuits on boatsare the only circuits that are exemptfrom the requirement for circuit pro-tection. The protection ratings forother DC motors fall into a gray area.In a perfect world, these motors wouldhave a circuit breaker built in, as inmost AC motors you may be familiarwith. (The little red reset button onthe side of the motor is actually a cir-cuit breaker.) However, most of theDC motors you’ll run into on boardyour boat do not have this type of

54


Figs. 4-14a, b. Meter test sequence for a circuit breaker. With one meter leadattached to a known good ground, check the feed side of the breaker for 12volts. With the breaker turned on, you should have 12 volts at the adjacentterminal on the breaker. If not, the breaker is faulty and must be replaced.

A

B

protection. So, why are motors different from any-thing else electrical found on board?

The answer to this question lies in the two majordifferences between motor circuits and other circuits.First, as already mentioned, motors will draw a con-siderable amount of additional current when theyfirst start up. Once the motor is running, the currenttapers off to a more reasonable and considerablylower level. This start-up current must be accountedfor, but a more serious possibility is a locked-rotorcondition that occurs when the motor is gettingpower but the armature is prevented from turning.This can be caused by corrosion in the motor hous-ing or bearings, or it can happen when a bilge-pumpmotor gets a piece of debris jammed in the pickupor impeller of the pump. When this happens, theflow of electrons increases dramatically.

The ABYC standards provide that the circuit pro-tection preclude a fire hazard if the motor circuit isenergized for seven hours under any conditions ofoverload, including locked rotor. The best way tomake sure you’re complying with this rule is to care-fully follow the installation recommendations pro-vided by the manufacturer. If you don’t have theprinted recommendations for the motor, call thecompany and ask for them. The only alternative isto test amperage drawn by the motor while it’s in alocked-rotor condition, and this is not a very practi-cal solution for the average boater.

Nonmotor CircuitsThe ABYC standards address circuit protection fornonmotor loads more clearly than they do protectionfor motor circuits. Basically, the rating of the fuse orcircuit breaker used on a nonmotor circuit must notexceed 150 percent of the maximum amperage of thesmallest conductor feeding the appliance. Odds aregood that when you determine the current of an ap-pliance, you’ll discover that you can’t buy a fuse orbreaker that falls at exactly the 150 percent value. Thekey words here are must not exceed. I generally workin the range of fuses and breakers that are between115 to 150 percent of the total amperage-handlingcapabilities of the circuit I am trying to protect andcan always find a match.

Distribution PanelsDistribution panels and switchboards fall into aslightly different category than regular on-boardequipment. The protection ratings for distributionpanels that supply multiple branch circuits are designed to protect not only the panel but also theprimary-feed conductor to the board. This may be animportant consideration if your boat’s original dis-tribution panel has blank sockets where more equip-ment could be added.

In general, in order to save money and weight,boatbuilders try to use the smallest wire sizes thatthey can get away with. If your boat came throughwith, let’s say, three blank holes in the distributionpanel where additional circuit breakers or fuses couldbe installed, you could have a problem. The boat-builder may have rated the wire going from the bat-tery to the panel for the loads he installed withoutany consideration for reserve capacity. As soon asyou add anything to the panel, you risk exceeding thecapacity of the feed wire.

The ABYC recommendations for dealing with thissituation are clear: “A trip-free circuit breaker or a fuseshall be installed at the source of power for panel-boards and switchboards, and shall not exceed 100percent of the load capacity of that panel, or 100 per-cent of the current-carrying capacity of the feeders.”There is an exception to this rule that will apply tomany newer boats: the fuse or circuit breaker for thewire that connects the battery to the distribution panelmay be rated at up to 150 percent of the capacity of thewire if the panel is equipped with a submain circuitbreaker rated at no more than 100 percent of the loadon the panel. Figures 4-15 and 4-16 on page 56 showthese possibilities and the allowable ratings.

Acceptable Locations for Fuses and Circuit BreakersThe next consideration you’ll need to make if you’readding electrical equipment to your boat is where tolocate the fuse or circuit breaker. Not all fuses andbreakers are mounted on the main distributionpanel, so some rules for placement of these devicesare needed.

55


56


Battery

+±

Switch Feeder

Panelboard

MainBreaker

MainBreaker

BranchBreaker

BranchBreakerBranchBreaker

Sub-mainBreaker

MAIN AND BRANCH CIRCUIT PROTECTION

Main Circuit Protection

See E-9.11.3.1Exception 2

MainBreaker

Feeders

Protection at Source of power

Distribution panel panelboard or switchboard

Source of power (battery)

Fig. 4-15. With this installation (submain breaker installed) the main circuit protector can be rated up to 150 percent of thefeeder wire ampacity. (© ABYC)

Fig. 4-16. Without a submain breaker (this panel has none), the feeder protection should be rated at no more than 100 per-cent of the feeder ampacity. (© ABYC)

E-11.7.1.2.1

The 7–40–72 RuleThe 7–40–72 rule of the ABYC’s standard E-11 is en-titled Overcurrent Protection and states: “Ungroundedconductors (positive power feed conductor) shall beprovided with overcurrent protection within a dis-tance of 7 inches (175 mm) of the point at which theconductor is connected to the source of power mea-sured along the conductor.” That means that the fuseor circuit breaker must be located no more than 7inches from the battery. There are some exceptionsto the 7–40–72 rule, as follows:

� Starter motor circuits are exempted from

circuit-protection requirements, and as already

stated, these are the only circuits on board that are

exempted.

� If a wire is connected directly to a battery terminal

and is contained throughout its entire length in a

sheath or enclosure (such as a conduit, junction

box, control box, or enclosed panel), the fuse or

circuit breaker should be placed as close as practi-

cal to the battery but no farther than 72 inches

(1.83 m) away. A common question that arises

over this exception is just what constitutes a sheath.

The black corrugated-plastic tubing used by most

production boatbuilders fills the bill for sheathing

and is a good, inexpensive choice.

� A wire not connected directly to the battery termi-

nal can be protected with a fuse or a circuit breaker

mounted as far as 40 inches (1.02 m) from the

point of connection as long as the wire is contained

in a sheath. For example, a large stud on the

starter-motor solenoid is commonly used to con-

nect various components on the engine. Wires so

connected can have fuses or circuit breakers lo-

cated as far away as 40 inches from the stud as long

as the wire is in a sheath—hence the 7–40–72 rule.

� Battery chargers (covered in chapter 6) add a de-

gree of complexity to the basic rule. Built-in battery

chargers, engine-driven alternators, and even solar

panels are all considered battery chargers, and the

rules go like this: “Each ungrounded (DC positive)

conductor connected to a battery charger, alterna-

tor, or other charging source shall be provided with

overcurrent protection within a distance of 7

inches (175 mm) of the point of connection to the

DC electrical system or to the battery.” This means

that if the charger is connected to the battery and

sheathed or enclosed, the fuse or circuit breaker

can be as far as 72 inches away (1.83 m) from the

battery. If the wire is sheathed, the 40-inch rule ap-

plies as long as the wire is not connected directly

to the battery.

� One additional exception that applies to many

newer powerboats is that no fuse or circuit breaker

is required on self-limiting alternators. This applies

to most alternators with internal voltage regula-

tors as long as the connection is not at the battery,

the conductor is in a sheath, and the wire is no

more than 40 inches long. The protection rating

must be based on the maximum rated output of

the alternator. Figures 4-17, 4-18, and 4-19 on page

58 illustrate the various allowable protection loca-

tions and the exceptions.

The above recommendations are intended tominimize the chance of an electrical fire on yourboat. But following these recommendations won’t doanything to protect the equipment itself. That’s whymany electrical appliances will also have a built-infuse. However, just because the device has a fuse builtin doesn’t mean you can wire it into your boat with-out supplying an additional fuse or circuit breakeras close to the battery as you can get it.

Wire Routing and SupportThe wire routing and support standards of the ABYCare intended to keep electrical wires from gettingburned, chafed, or soaked by bilge water. It’s impor-tant to think dynamically when installing any newwiring or repairing old wiring. Conditions changedramatically when your boat is underway in a roughsea with engine parts spinning away and exhaust atfull temperature. Improperly routed wires and bun-dles of wire collected into harnesses can be damagedby spinning pulleys and shafts; harnesses without alittle slack to allow for flexing of the engine mountscan be pulled apart; and the insulation on wires and

57


cables near a hot exhaust manifold can melt awayfrom the heat.

The rules for routing wires are simple, and com-mon sense will go a long way toward keeping thingsright.

� Harnesses, unless they run through a conduit or

built-in channel, need to be supported at least every

18 inches (45.7 cm).

� AC and DC conductors should never be bundled

together unless separated by sheathing.

� Grommets must be used when running wires

through cutouts in bulkheads and fiberglass pan-

els. Some acceptable types are illustrated in figure

4-20.

� Wires must be kept as high above the bilge as pos-

sible, and those wires that must live there (such as

the bilge pump wiring) should have waterproof

58


72" max

7" or 40" max

Overcurrent protection device (fuse or circuit breaker)

Conductors to various loads as needed (no length restriction)Starter

Battery

Cranking motor conductors (no length restrictions)

SINGLE BATTERY (See E-9.11)

7" or 40" max

Conductors to various loads as needed (no length restriction)

Starter


NO BATTERY SWITCH (See E-9.11)

Battery 72" max

72" max

Overcurrent protection device (fuse or circuit breaker)

DUAL BATTERY (See E-9.11)

Conductors to various loads as needed (no length restriction)


7" or 40" max

Fig. 4-19. Circuit protection in a dual battery installation.(© ABYC)

Fig. 4-17. Figure 15 from section E-11 on battery supply circuits, showing the location of overcurrent protection. (© ABYC)

Fig. 4-18. Battery supply circuits with no battery masterswitch installed. (© ABYC)

(See E-11.12.1.2) (See E-11.12.1.2)

(See E-11.12.1.2)

connections. Sealing heat-shrink tubing works well

in these cases. (See the circuit-repair section of this

chapter.) All wiring should be routed at least 2

inches (50.8 mm) from wet-exhaust-system com-

ponents and 9 inches (22.9 cm) from dry-exhaust

components.

Methods of securing wire can be as simple as us-ing nylon wire ties with screw holes for attachment.The recommended method of securing wires run-ning above or near moving machinery is to use theplastic-dipped or rubber-insulated metal fastenerscommonly found on standard engine installations.Figure 4-21 on page 60 shows a variety of acceptablewire-securing devices.

Connecting the Dots: Making Wiring and Connection RepairsIn making repairs to existing wiring or building anew circuit for the latest electrical appliance you’vepurchased, proper techniques and components canmake all the difference in the world when it comesto preventing problems later. Take the time to do thejob right and do it once.

Soldering TerminalsOver the years there has been some controversy anddiscussion among electricians regarding solderingversus crimp-type connectors used in electricalwiring on boats. For years I labored over each con-

59


Electrical Tape Wrap Grommet

PVC Pipe Silicone AdhesiveFig. 4-20. Acceptable methods of providing abrasion protection through bulkheads.

nection, carefully soldering each lead. I consideredcrimp-on terminals to be the easy way out and infe-rior to soldered terminals. Well, times have changedand so has my view of the proper way to attach ter-minals to the ends of wires. In fact, I no longer usesolder for any of my connections. Crimp technologyhas improved significantly so that if the crimps areapplied correctly, you won’t have any problems withthem at all. Premier boatbuilders are using crimpconnections exclusively with no problems, and I’mnow convinced that crimping connectors is more

practical than soldering them. It’s certainly a lot moretime-effective.

Once again, our friends at the ABYC have pro-vided some guidance. In their view, solder must notbe used as the sole means of connecting terminals towire. The connection must first be mechanically fas-tened (crimped) and then soldered. They do makean exception, however, relating to battery terminals:Battery terminals may use only solder as long as thecable enters the terminal at a minimum distance of1.5 times the diameter of the conductor (the batterycable itself). This is shown in figure 4-22.

The reasoning behind the ABYC’s crimp-plus-sol-der recommendation for connections may not beclear to the novice electrician. Excessive current cangenerate enough heat in a poor-quality connection tomelt the solder, allowing the terminal to come un-done. I recommend that you stick to crimping, fol-lowing the guidelines given here.

First select the correct terminal. Figure 4-23 showsthe preferred types, all “captive” by definition. “Cap-tive” means that if the screw or nut holding them inplace comes loose, they won’t fall off the shank of thescrew or stud. The figure also shows some types thatshould never be used. Don’t ever wrap the bared endof a wire (without a properly attached terminal)around a screw and tighten it in place. With strandedwire (the only type you should be using) it’s quiteeasy to have some of the strands squeeze out, and theycan end up touching an adjacent terminal, causing ashort circuit.

60


Fig. 4 -22

X

Fig. 4-21

Fig. 4-22. The rule for soldering battery cable ends.

Fig. 4-21. Tie-wraps and other acceptable clamps for securingwiring harnesses.

When selecting terminals, refer to the color codesand match the terminal color to the appropriate wiregauge. The colors are as follows:

Red 18–16 gaugeBlue 16–14 gaugeYellow 12–10 gaugeBurgundy 8 gauge

Never crimp a wire into a larger terminal that’snot the correct size. Either the connection will nothold or you’ll lose some of the strands in the wire,creating an increase in resistance.

Crimping tools have changed over the last fewyears. Today’s ratcheting crimping tools do a finejob and take away the big question, did I squeeze thepliers hard enough? These crimpers are easy to use;all you do is squeeze the handles until the ratchetsnaps, and you can be sure the connection has beensqueezed hard enough.

One disadvantage to these new crimpers is thatmanufacturers have designed them to use only theirown terminals. Thus, you can only be certain of the

integrity of the crimp if you use terminals designed tomatch the crimper. This is not a huge problem if youbuy your supplies at the same place you bought thecrimper, but be aware that the crimper you buy maynot be compatible with all brands of terminals. Fig-ure 4-24 shows my crimper, made by Ancor.

61


Unapproved wire connector

Approved wire connectors

Fig. 4-23. Preferred types of connectors, and types that are not allowed.

Fig. 4-24. Ancor ratcheting crimper. By using this type ofcrimper, you can be assured that all your connections will becrimped properly as long as you use the tool correctly.

For wire stripping, I use the end-type strippershown in figure 4-25. This stripper is adjustable sothat the exact amount of insulation can be removedfrom multiple pieces of wire, and the risk of cuttinginto the wire strands is minimized.

Both the crimper and the wire stripper are avail-able through West Marine and all the major marinesupply stores. At about $140 for the pair, this combi-nation is a really good investment and will make your

work much easier. Figure 4-26 shows the stripper inuse, and figure 4-27 shows the crimper in use.

About 1⁄4 inch (6 mm) of insulation should bestripped off the wire before it’s inserted into the ter-minal ferrule. The stripper mentioned above allowsyou to set the amount of insulation to be removed inmillimeters. The correct match of wire and connectoris illustrated in figure 4-28. The ends of the wire justbarely protrude from the ferrule of the terminal.

62


Fig. 4-27. Ratcheting crimper in use. Fig. 4-28. The correct amount of wire protrusion throughthe barrel of the connector.

Fig. 4-25. End stripper. I love these tools because you can ad-just the amount of insulation to remove for a really goodmatch to the crimp connector. One drawback is that theyonly work on wire up to 10 AWG.

Fig. 4-26. End stripper in use.

Make sure the crimper is in proper orientationwith the terminal. For all but the butt-type connec-tor, the handles of the crimping tool must be in thesame plane as the ring or blade of the terminal, asshown in figure 4-29. For butt connectors, this really

doesn’t matter, but be sure both crimps align in thesame plane. Always test your crimps by pulling onthe wire hard enough to be sure they’ll hold.

The newest variety of crimp terminals comes withheat-shrink casings preinstalled. After you crimp theterminal to the wire, heat the terminal with a heatgun, and the insulation will shrink tight around theterminal and seal it against moisture. This is a supe-rior method of applying a terminal to a wire, butthese terminals cost approximately a dollar each atthis time.

When splicing a group of wires in a harness, it’s agood idea to stagger the butt connectors so you don’tend up with a bunch of them in one spot. Figure 4-30illustrates what can happen. A better approach isshown in figure 4-31.

At some point you may find yourself having to re-pair or replace a gang plug. There are many types ofthese plugs available, and it’s usually best to replacethe entire plug assembly rather than to replace a sin-gle connector within the assembly. Replacing only apart of the plug rarely works and the watertight in-tegrity of the plug is almost always ruined. Duplexand triplex assemblies are available at the major sup-ply houses, and repairing these may also require re-placing both the male and female ends of the plug.

63


Fig. 4-29

g

Fig. 4 -31

Fig. 4-31. Staggered butt connectors at a harness repair point. Using this approach to harness repair will give a much neater job.

Fig. 4-29. Orientation of the plier jaws with the connector tomake a proper crimp.

Fig. 4-30. A “bunch” of butt connectors at a harness repair point. Taped and wrapped as it should be, this would look like asnake trying to swallow a rat!

Finally, whenever you join two wires with buttconnectors, I strongly recommend that you seal themwith a length of heat-shrink tubing to make a water-tight connection. These terminals are famous fortrapping water and corroding. Figure 4-32 shows abutt connector that has been crimped and sealed withheat-shrink. Heat-shrink tubing is now available with

a sealer that’s perfect for making waterproof connec-tions anywhere on board.

Another new addition to the electrician’s arsenalis the dual-gauge butt connector. These stepped con-nectors provide a solution to the age-old problem ofconnecting a smaller wire to a larger one. Figure 4-33 shows one of these new connectors.

64


Fig. 4-32. Butt connection with waterproof heat-shrink tub-ing. This is the highly recommended method for joining twowires together, especially in the area of the bilge.

Fig. 4-33. “Stepped”-type butt connector. These are the onlyway to go when you need to join two wires of differentgauges.

65

Of all the modern inventions that make life as weknow it possible and, more important, make it pos-sible for us to spend our weekends and holidayswhizzing around various bodies of water in ourpowerboats, the 12-volt battery has to be one of themost important. Without that little plastic box fullof acid and lead sitting in the bilge and the flow ofelectrons within it in a direct current path, our boatsand boating wouldn’t even vaguely resemble thesport we love and enjoy. All but the smallest dinghiesand skiffs with hand-crank motors rely on batteriesfor everything from starting the motors to keepingthe beer cold. Without that battery, you and I wouldbe rowing, and as much as I admire healthful exer-cise, that idea lacks pragmatic appeal.

Oars worked just fine for great-granddaddy, but Ienjoy flipping switches. With a flip of the first switchthe out-drives lower into the water; with a flip of an-other switch the exhaust fans clear the bilge of fumes.Flipping the next switch turns on the VHF for the lat-est weather report. Finally, with a twist of the starterswitches the engines rumble to life and I am away fora day on the water. None of this would happen with-out the boat’s batteries, so let’s take a close look atthis most extraordinary and complicated contrivance.

How Batteries Work: The BasicsIn direct defiance of the wishes of one of my editors,I have decided to avoid a long dissertation on thechemistry that boils between the plates of your boat’sbatteries. For one thing, battery chemistry is a com-plicated subject that would take many pages to prop-erly discuss. And for another thing, it’s not what thisbook is about. I want you to know how the electricalsystem on your boat works and what to do when itdoesn’t. The internal chemistry of the battery just isn’t that important. However, for you technophileswho do want to delve deeper into the chemical mys-teries of the modern voltaic storage battery, I would

refer you to your public library and the EncyclopediaBritannica where you’ll find an exhaustive (and ex-hausting) article on the subject.

Basic ChemistryUnfortunately, I am not going to be able to avoidchemistry altogether, and there are a few underly-ing principles with which you should be familiar.For our purposes it’s enough to know that the sev-eral types of storage batteries you might find on yourboat all work on the same system. Batteries are di-vided into cells with plates of two dissimilar metalssurrounded by an electrolyte. An electrolyte can beany electrically conductive material (electrolytes arean important component in popular energy drinkslike Gatorade), and when any two metals are sus-pended in it they will produce an electrical voltagebetween them. (Voltage, you’ll remember, is the po-tential to produce electrical current, and thus, is theonly electrical value that’s static.) The magnitude ofthe voltage will always be different for different com-binations of metals and electrolytes.

The electrolyte used in your boat’s batteries (aswell as in your car batteries) is sulfuric acid, and thedissimilar metals are lead dioxide in the positiveplate (or cathode) and sponge lead (a porous form ofpure lead) in the negative plate (or anode). Thus, allsuch batteries are called “lead-acid” batteries.

As a lead-acid battery is discharged, the acid elec-trolyte is chemically converted to water (this ex-plains why batteries can freeze and why the specificgravity changes, all of which we will cover later), andthe plate material is converted to lead sulfate. Torecharge a battery, you pass through it a 12-voltcharge that converts the three active materials backinto their original state. The actual chemical formulafor this process when set in 10-point type is some 4inches long, which is why I decided not to go into itany deeper than we have just done.

Batteries and Battery SystemsChapter 5


66


The only other ingredients in your boat’s batter-ies are the grid, an inert (plastic) frame on which thesolid active ingredients are suspended in the elec-trolyte, and the case. Lead dioxide, sponge lead, andlead sulfate are all very soft and fragile. The gridgives the plates the support they need to stand up tovibration and shock. The case, of course, containsthe entire contraption and insulates one cell fromthe next.

The voltage from a single cell in a fully chargedlead-acid battery will always be approximately 2.1 volts (called the galvanic potential), regardless ofthe size of the battery. A lead-acid cell the size ofyour house is going to produce the same voltage asone the size of a peanut. Thus, when six of thesecells are strapped together in series (positive to neg-ative and negative to positive), you have a standard12-volt battery.

Recent engineering innovations have allowedmanufacturers to produce plates that are slightlythinner than their predecessors but just as electricallycapable. And due to advances in material technology,the new plates are much stronger than the old ones.Figure 5-1 shows the construction of a typical 12-voltbattery with cell dividers and internal plates.

Types of Lead-Acid BatteriesThere have been enormous advances in battery tech-nology in the past few years, and the result is a largeand growing assortment of batteries that you can useon your boat. The days of the massive black case withgooey sealer and exposed lead cell-connecting bars arefading into history. Many of the heavy-duty commer-cial batteries are still constructed in the traditionalmanner, but even here things are changing fast. We now have low-maintenance, no-maintenance, cranking, deep-cycle, gel-cell, AGM (absorbed glassmat), standard automotive, and even special golf-cartbatteries.

Which is just the right choice for you and for yourboat? Well, that depends on what you’re going to dowith the battery once you buy it. Many boats todaywill have at least two types of batteries on board, andsome will have more than that.

To start, we can eliminate the standard automo-tive battery from all but incidental marine applica-tions. These batteries might look just like their marinecounterparts, but they are very different. Automotivebatteries, even the so-called heavy-duty ones, arelightly constructed with thin plates hung on fragilegrids; even the cases are thin plastic. This is becauseyour automobile just doesn’t need a big, heavy bat-tery. Your boat, however, does need a big, heavy bat-tery, and car batteries wouldn’t last very long in themarine environment. Marine batteries must stand upto the vibration and deep states of discharge com-mon on boats, and they must be able to withstand lev-els of neglect and abuse to which you would neversubject your car battery.

The difference between batteries is not only in thephysical construction but in the ratios of lead perox-ide and other materials such as antimony and a cal-cium alloy used in constructing the battery’s plates,and in the amount of material used in the plates.These variations affect the number of times a batterycan be cycled (the number of times a battery can bedischarged and then recharged) and still come backto useful life.

The construction of a battery also affects howlong it can remain discharged before the lead sul-fate hardens to the extent that recharging can’t re-verse the chemical reaction. When this happens, the

Fig. 5-1. A typical 12-volt battery.

67

Batteries and Battery Systems

battery is said to be sulfated and must be replaced.These chemical and construction variations in bat-tery types also explain why some batteries have atendency to produce more hydrogen (a processcalled gassing) than others.

Engineers have been able to reduce gassing to al-most nothing by adding antimony into the plate ma-terial. Less gassing means less water loss, and hencethe evolution to the sealed batteries which are be-coming the norm today. We now enjoy modern gel-cell or absorbed-glass-mat (AGM) technologies thatkeep the sulfuric acid in either a gelled state or ab-sorbed in a mat material, much like conventionaldry-cell batteries.

The first basic choice you’ll have to make as youtry to pick out a battery for your boat is between theold-technology wet-cell batteries, the new gel-cellbatteries, and the even newer absorbed-glass-mat(AGM) batteries, so let’s take a close look at each ofthese three.

Wet-Cell BatteriesWet-cell battery technology has been around sincethe days of the first electric-start automobiles. Thisis the type of battery with the removable cell caps(generally, but not always) with which we are all fa-miliar, because it’s the type still found under thehood of the family car. Wet-cells have the lead platessuspended in liquid electrolyte, and the durability ofthe individual batteries depends on the robust con-struction of the case and grids as well as the amountof material in the plates.

Even today, wet-cell batteries offer some impor-tant advantages over gel-cell and AGM batteries, thenew kids on the block. They are usually the cheapestto buy initially and, as we will see below, they are byfar the cheapest to use over the long haul—provided,of course, that you don’t neglect regular mainte-nance. They also stand up well to abuse such as over-and undercharging.

The disadvantages of wet-cells are that they re-quire more elaborate ventilated battery compart-ments. They will not hold a charge as long as thenewer gel-cells and AGMs, which means that theycan’t be left unattended for as long. They must be

kept upright at all times, and they require regulartopping-up with distilled water.

Gel-Cell BatteriesGel-cell batteries work on the same principles as wet-cells, and the materials are basically the same. The bigdifferences are that the electrolyte is rendered into apaste about the consistency of grape jelly, and theplates (which have a slightly different composition,to reduce gassing) are suspended in this goo. Sincethere is no liquid to top up, there is no need for thefamiliar caps, and the cells are, for all practical pur-poses, sealed.

There are several important advantages to gel-cellbatteries. You don’t have to worry about spilling theelectrolyte by tipping the case over, for one thing. Infact, gel-cells work just fine on their sides or evenupside down. They hold a charge much better thanwet-cells and can be left unattended for longer peri-ods of time—and, of course, you don’t have to worryabout topping-up the electrolyte.

The disadvantages of gel-cells, besides the cost(which we will go into below), are that they cannot beovercharged without suffering permanent and oftenterminal damage. Also, because the electrolyte can’tcirculate between the plates the way it can in a wet-cell battery, gel-cell plates must be kept thin enoughto accept a charge in a reasonable length of time.

Generally, over the last few years, gel-cells have de-veloped quite a bad reputation for not living up to theclaims made for them by manufacturers. Moreover,gel-cells have charging needs that differ from both theAGM (which we will discuss next) and wet-cell bat-teries. Traditional constant-rate ferro-resonant bat-tery chargers, which are found on all older boats andon new high-production boats (Sea Ray and Bayliner,to name two), have destroyed many gel-cell batteries.Gel-cell batteries must be charged using a three-stagesmart charger (covered in chapter 6) with the voltageset for gelled electrolyte.

Absorbed-Glass-Mat BatteriesAbsorbed-glass-mat batteries are also of the no-maintenance type. They have a sealed case, just liketheir gel-cell cousins: you couldn’t add water to these

68


batteries if you wanted to. The primary difference be-tween AGM batteries and gel-cells is in the way theelectrolyte is supported. AGMs have a fiberglass matbetween the cells that further supports the electrolyte.There are other important differences, though. Testshave shown that AGMs are less sensitive to chargerates than gel-cells, perhaps making them a betterchoice if you own an older boat with a constant-ratecharger. (More on chargers in the next chapter.)

No-Maintenance BatteriesBeware of batteries sold by some chain stores suchas Sears and Wal-Mart that purport to be no-maintenance batteries and lack a filler cap just likegel-cells and AGMs. These are often wet-cell auto-mobile batteries that have an internal reservoir ofelectrolyte that’s gradually used up as the battery isrecharged. Once this reservoir is gone, the batteriesare junk. These might be fine for your car, but theyhave no more business on your boat than any otherautomobile battery. A few may even be marketed asmarine batteries, so be extra careful when buyingfrom discount stores. The best policy is to buy yourbatteries from a reputable supplier who specializesin batteries for boats.

Battery LifeBut what about charging cycles? How many timeson average can the different types of batteries be dis-charged and recharged before they need to be re-placed? This is a difficult question, because thenumber of charging cycles that you can expect outof a battery depends upon the rate and depth of dis-charge, the recharging method, and the quality of thebattery construction. Also, batteries of the samenominal size will often have different amp-hour ca-pacities, and the real concern is cost per amp-hour.The Typical Battery Charging Cycles table aboverepresents the average number of times top-qualitybatteries of each type can be discharged andrecharged. Cheap substitutes will provide a muchlower average number of cycles.

Cost ComparisonsConventional wet-cell batteries are the least expen-sive of the three types we have discussed, no matter

which way the cost is measured. The question is, if Ibuy the new gel-cell or AGM batteries, what am I get-ting for my extra battery dollars? Are the AGM andgel-cell batteries worth the extra money? The answeris that there is no answer—at least not one that fits allcircumstances. The type of battery that’s best for youdepends on your needs and the use to which you putyour boat. Here are some cost comparisons.

Comparing charging cycles to typical cost per bat-tery gives you a feel for the true cost of these batter-ies over the long haul. Using a group 27 battery (acommon size) for comparison gives a cost-per-cyclebased on the average number of cycles in each typeused above.

The table below compares typical group 27 deep-cycle battery prices taken from the 2006 West Marinecatalog, and the average true cost per cycle.

Using a cost-per-amp-hour calculation, we canuse the advertised total amp-hour capacities for thethree group 27 deep-cycle batteries West Marine listsin the same 2006 catalog to arrive at cost over life ofthe battery (see table on the next page).

Typical Battery Charging Cycles

Battery Type . . . . . . . . . . . . . . . . . . . . .Cycles

Conventional wet-cell . . .800–4,500 cycles (2,650 avg.)Gel-cell . . . . . . . . . . . . .800–2,000 cycles (1,400 avg.)AGM . . . . . . . . . . . . .1,000–5,000 cycles (3,000 avg.)

Note: The above averages are based on manufacturer’s claims underideal conditions. Actual averages will be considerably lower in theless-than-ideal conditions found on your boat.

Deep-Cycle BatteriesCost Per CycleBattery Type . . . . . . . . . . . . . . . . . . . . . . .Cost

Wet-cell . . . . . . . . . . . . . . . . . . . . .$100, 3.8¢ per cycleGel-cell . . . . . . . . . . . . . . . . . . . . . .$213, 15¢ per cycleAGM . . . . . . . . . . . . . . . . . . . . . . . . .$200, 7¢ per cycle

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Please keep in mind that these costs are based oncharge-cycle numbers that are quite high. In actualuse, your cost per amp-hour will probably be muchhigher. However, on average the findings here are asgood for comparison of battery types as any othermethod.

Although they will require more maintenancethan other types, conventional wet-cell batteries arestill the least expensive of the three types to buy andown over the long haul. AGM batteries offer all theadvantages of the gel-cells plus a less-finicky chargecycle. Therefore, in almost all applications, AGMs area better choice than gel-cells, but as of this printingyou’ll still pay a substantial premium for AGMs overwet-cell batteries. AGMs are a particularly goodchoice for installations where acid spills are a consid-eration, as with personal watercraft (Jet Skis) andother sport boats, and they are excellent for use onboats that will be left unattended for months at a time.

Which Battery Is Right for You?All but the smallest open boats should have at leasttwo batteries. The starting battery is for starting theengine and needs a lot of cranking capacity to spina heavy-duty starter motor. The house battery is usedto run equipment such as cabin lights, stereos, re-frigerators, and electronic equipment that isn’t con-nected to the engine. The starting battery should be

a heavy-duty marine cranking battery, and the housebattery should be a deep-cycle marine battery. Oneof my boats, a 15-foot dory I use for bay fishing, hasa single deep-cycle battery that I use to operate myfish-finder and running lights at night. The engineis a pull-start outboard, so I don’t need a crankingbattery. If I had an electric-start engine on this boat,I would consider an additional cranking battery,even for a boat this small. I hate paddling; it justtakes too long against a 2-knot tide.

My other powerboat, a 25-foot V8-poweredwalk-around, is set up with a group 27 cranking bat-tery and a group 27 deep-cycle marine battery.

Deep-Cycle versus Cranking BatteriesThe difference between cranking and deep-cycle bat-teries is simple. Cranking batteries are designed toprovide a burst of cranking power for a short periodof time. Once the engine is running, the engine’s al-ternator will kick in and quickly recharge the bat-tery, replacing the power used to start the engine.Cranking batteries are not designed to be dischargeddeeply over and over again. You would be lucky toget one season of boating out of a cranking batteryused as a deep-cycle house battery.

Deep-cycle batteries, on the other hand, are builtwith heavy and comparatively thick plates and havemuch more lead in them than cranking batteries.You can actually tell the difference between the twoby lifting them. They are designed to be dischargedup to 50 percent of capacity and recharged over andover again without sustaining any permanent dam-age. Because of the heavier and thicker plates usedin deep-cycle batteries, they take much longer toreach full charge than cranking batteries. Therefore,they aren’t a good choice for a starting battery, par-ticularly where an engine will be started frequentlyand run for short periods of time.

Deep-cycle batteries are perfect for use as thehouse battery in cruisers that will be anchored awayfrom shore power for overnight trips or for fishingboats that will be anchored for long periods with thefish-finder, radio, and beer cooler running.

Deep-cycle batteries are designed to take abuse,but even these can’t be completely discharged andrecharged continually without failing. Thirty percent

Deep-Cycle BatteriesCost Over Life of the BatteryBattery Type . . . . . . . . . . . . . . . .Cost Formula

Wet-cell . . . . . . .90 amp-hours ÷ 2 (50 percent discharge)= 45 amp-hours x 2,650 cycles

= 0.0017¢ per amp-hourGel-cell . . . . . . .86 amp-hours ÷ 2 (50 percent discharge)

= 43 amp-hours x 1,400 cycles= 0.0027¢ per amp-hour

AGM . . . . . . . . .92 amp-hours ÷ 2 (50 percent discharge)= 46 amp-hours x 3,000 cycles

= 0.0014¢ per amp-hour

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of full capacity is generally considered a maximumlevel to which these batteries can be safely discharged.Fifty percent maximum discharge, however, providesa major increase in the life of the battery.

Combination BatteriesWithin the last few years I have seen what could bethe answer to the battery prayers of many ownerswhose boats are not clear candidates for either purecranking batteries or pure deep-cycle batteries. Pre-viously owners of these borderline boats were forcedto choose between two imperfect options. We nowhave batteries advertised as combination cranking/deep-cycle units that are a perfect solution for theweekend powerboater who occasionally spends thenight camping or fishing at anchor and spends therest of the time at the dock plugged into shore power.

Combination batteries offer a compromise inperformance. They won’t be as capable of sustainingrepeated deep discharging and recharging as a truedeep-cycle battery, but they will be fine for occasionaldeep-cycle use and more than adequate for startingyour engine. As with any battery, a combination unitmust be sized to fit your specific needs and the needsof your boat.

Some Specific RecommendationsLet’s sum up all this various information and makea few specific recommendations for the right batteryto put into your boat.

� Small, open boats with manual-start engines, min-

imal electrical gear, and possibly an electric trolling

motor need one or two deep-cycle batteries

matched to amperage needs.

� Personal watercraft need a single AGM or gel-cell

battery large enough to meet engine-cranking re-

quirements.

� Outboard center-console boats need dual combi-

nation batteries, with one for starting and one to

run the electronic systems.

� Water-ski boats need a cranking battery or a com-

bination unit of a size dependent upon the size of

the engine and amperage requirements.

� Weekend cruisers need either one cranking bat-

tery for the engine and a separate deep-cycle bat-

tery for the systems, or two combination units,

depending on amperage requirements and amp-

hour loads.

� Long-range cruisers need cranking batteries large

enough to meet engine requirements and enough

deep-cycle capacity to meet total daily amperage

requirements.

When you’re choosing a battery for your boat andyou find that you can’t decide between units of twopower ratings, always go with the larger of the two.There is seldom any trouble with a battery that’sslightly too big, provided that it fits into your bat-tery box, but one that’s too small can open up aworld of problems. When you really need your bat-tery, you won’t need a dead one, so always err on theside of too big rather than too small.

Batteries for CruisersIf you’re a cruiser and spend days away from thedock, you need to get serious about batteries. Yourneeds are completely different from the day-trippingwater-skier or fisherman. First, you should do anelectrical-load survey on your boat and calculate theextent of your electricity needs while unplugged fromshore power. This survey will help determine how biga battery you need and establish how many amp-hours you’ll need in it. You need a dedicated start-ing battery and a separate house battery to run theequipment you’ll be using while the engine is notrunning.

To do the survey, make a list of all the electricalequipment you have on your boat. List everythingfrom the fish-finder to the light in the refrigerator.Now refer to the average power ratings found in fig-ure 3-15 on page 37 and honestly estimate your av-erage daily use of each item on your list. Multiplythe amp-hours by the number of hours (or fractionof hours) for each item to get the amp-hours usedeach day by each piece of equipment. Next, add upthe amp-hour-per-day figures, and the total willgive you a pretty good idea of your total daily amp-hour consumption. Now double your daily amp-

71


hour figure, remembering that youdon’t want to discharge the batteries tobelow a 50 percent charge, and you havean accurate amperage rating for yourhouse battery. Purchase your batteriesaccordingly, and remember, when itcomes to deep-cycle batteries, cold-cranking amps is an irrelevant number.You need to be concerned only with theamp-hour capacity, sometimes knownas the 20-hour rating.

The 20-Hour RatingThe 20-hour rating of a battery specifies theamount of amperage it can supply for 20hours at 80°F (27.7°C). Figure 5-2 showsthe correlation between typical battery sizeby group number, amp-hour rating, andcold-cranking amps. Never assume amper-age capacity based on size or group cate-gory of a battery. Always check the actualbattery specifications with the seller. Youmight just find that a bargain battery mightnot be such a bargain after all.

Marine-Cranking Amps versusCold-Cranking AmpsMost medium-sized boats need a cranking batterywith enough cold-cranking amperage (CCA) to getthe engine going, but it isn’t that simple any more. Anew classification has been added to the mix, andsome vendors are now rating the batteries they sellin marine-cranking amps (MCA) in place of cold-cranking amps.

As defined by the ABYC, the two definitions are

“Battery cold-cranking performance rating—The dis-charged load, in amperes, that a battery at 0°F( 18°C) can deliver for 30 seconds and maintain avoltage of 1.2 volts per cell or higher.

“Cranking performance (also referred to as marine-cranking amps at 32°F or MCA at 32°F)—The dis-charge load, in amperes, that a new, fully chargedbattery at 32°F (0°C) can continuously deliver for 30seconds and maintain a terminal voltage equal to orhigher than 1.20 volts per cell.”

Notice the 32° variation in the two ratings. Thismeans that if two batteries with the same amper-age—one using the MCA rating and the other usingthe CCA rating—are being considered, the one us-ing the CCA rating will be the more powerful battery.Battery potential decreases with temperature. So, abattery that can put out an equal amount of amper-age cranking at temperatures 32° colder than thecompetition is theoretically a more powerful battery.

What does all this mean? Simple: Be careful! Doyour homework and know what you’re buying beforeyou pay your money. Manufacturers constantly playgames with these numbers. If you’re getting your bat-teries at the local Sears or KMart, don’t expect thefloor people to know any more than you do aboutbattery ratings.

Typical CCA ratings for starting gasoline enginesare shown in the following table.

Diesel engines, depending upon the type ofstarter motor and actual engine displacement, can

Fig. 5 - 2

7"10.5"

9"

12" 7"

9"

9"21"

10"

2 x 10.5" = 21" 7"

11"

21" 11"

10"

24 27

4 - D

6VGolf

6VGolf

8 - D

Battery Amp-hours CCA24 85 500–70027 100 550–8004-D 150–180 10008-D 200–225 1175GOLF 200–225 1500–1600

Fig. 5-2. Common battery group sizes, amp-hour ratings, and dimensions.

72


theoretically require twice as much amperage capac-ity as the figures above! When in doubt, consult theengine builder for the exact specification.

Again, if you have a cruiser with a lot of aux-iliary equipment, you’ll need a battery bank comprisedof deep-cycle batteries. Use the amp-hour-per-day for-mula above to calculate the total amp- hour capacity.

Battery SafetySafety considerations around lead-acid batteries areoften not taken seriously. During my career, I’ve seentwo batteries explode, covering workers with acid.In one instance we were able to flush away the acid sothat the worker escaped injury. What was his mis-take? He left a 1⁄2-inch wrench on top of a battery, andit had come in contact with both the positive andnegative terminals.

In the other instance, the victim was permanentlyscarred. His error? He disconnected a battery chargerfrom a battery without first turning off the charger.The resulting spark ignited the hydrogen gas that hadbuilt up around the battery.

In a third, less-dangerous instance, a battery sim-ply exploded and coated the main saloon of a friend’sliveaboard cruiser with battery acid—curtains, carpets,furniture, everything. I’m not sure what caused thatone, but I think he was attempting to charge a batterywith low electrolyte. Fortunately, no one was on boardat the time of the explosion so there were no injuries.

Battery acid is dangerous. Battery safety rules aresimple but must be followed.

� Thoroughly ventilate the area around batteries.

Highly explosive hydrogen gas, which can be ig-

nited with the smallest spark or cigarette ash, is be-

ing produced when charging a battery.

� Don’t put tools on top of a battery when working

in the area. Metal tools can cause a short between

the two terminals and will literally weld themselves

to the battery. The least you can expect is a spec-

tacular spark that could easily cause an explosion

or serious burns. Also, wearing jewelry when work-

ing around batteries is risky, for the same obvious

reasons.

� When connecting or disconnecting battery termi-

nals, always disconnect the negative terminal first

and hook it up last. This sequence minimizes the

chance that a spark can jump the gap between the

battery post and the cable-end terminal as you

hook it up.

� Don’t smoke. If you must smoke, don’t do it

around batteries.

� Batteries are heavy. Use the carrying handles pro-

vided on good marine batteries and get help if you

need it. If your battery doesn’t have carrying han-

dles, borrow a special battery-carrying strap, as

shown in figure 5-3, and use it.

� Don’t overfill wet-cell batteries. The excess elec-

trolyte will boil out as the battery charges, leaving

an acid film all over the battery and everything in

the surrounding area. Figure 5-4 shows the proper

level to which each cell should be filled. When the

level is correct and you look down into the cell, you

should see a fish-eye staring back at you.

� Never attempt to recharge a frozen battery; it will

probably explode. A frozen battery must be com-

pletely thawed before any attempt is made to re-

store it. Odds are that it’s dead anyway.

� Never attempt to charge a battery that has elec-

trolyte levels that are below the top of the battery

plates. On sealed batteries with a charge-indicating

“eye,” various colors are used to indicate the state of

charge. Depending on the manufacturer, one of the

colors will indicate electrolyte loss. This battery

Battery CCA Ratingsfor Gasoline EnginesEngine Size . . . . . . . . . . . . . . . . . .CCA Rating

Four-cylinder engine . . . . . . . . . . . . . . . . . . . . .450 CCASix-cylinder engine . . . . . . . . . . . . . . . . . . . . . .550 CCASmall V8 (350-cubic-inch, 5.7-liter) . . . . . . . . . .650 CCALarge V8 (454-cubic-inch, 7.4-liter) . . . . . . . . . .700 CCA

73


should not be charged, but replaced. Sealed batter-

ies should have a sticker on the top explaining the

color codes.

� Keep batteries in a properly designed box secured

to prevent battery movement in rough seas. Make

sure that all cable connections are tight and perma-

nent. No alligator clips or twisted-on connections

are allowed.

� Keep batteries clean and free from corrosion and

any moisture or oily film on the battery top. This is

not only a safety consideration but also a great way

to increase the life of your batteries.

� Know which battery terminal is positive and which

is negative. This is important for the connect-and-

disconnect procedures described above. It will also

prevent damage to polarity-sensitive equipment like

GPS and radar.

� Battery terminals should be marked with a plus (+)

or minus ( ) sign, or the positive terminal may be

marked with red paint. With a post-type battery,

the positive terminal is always slightly larger in

diameter than the negative. Don’t believe the cable

colors. Lots of people replace cables with whatever

color cable is available at the time they needed a

new one. Be absolutely certain you know which is

the positive and which is the ground (negative)

cable.

Remember, battery electrolyte is sulfuric acid. Itwill burn through shirts, pants, shoes, wood, mostmetals, and your skin. Anything exposed to batteryelectrolyte should be thoroughly flushed and imme-diately rinsed in fresh water. Even then, your favoritejeans or T-shirt will probably end up with a souvenirset of holes after the first wash.

Battery LocationA major part of battery safety is directly related tothe way batteries are installed in your boat. Ourfriends at the ABYC have addressed this issue insection E-10 of the Recommended Standards.They list three acceptable possibilities for batteryinstallation.

Cell opening with cap removed,showing correct fill level

Electrolyte

Cell plates

Fig. 5-3. Battery carrying strap in use. This type of strap as-

sembly will only work for smaller group 24 and 27 batteries.

Larger batteries all have carrying handles attached, and

should be handled by two people.

Fig. 5-4. Correct battery cell fill level.

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1. Covering the positive battery terminal with aboot or nonconductive shield

2. Installing the battery in a covered battery box

3. Installing the battery in a compartment spe-cially designed only for the battery or batteries

In addition, there are a few other rules in thestandards with which you should be familiar.

� The battery should not be located near fuel-

system components such as lines, filter canisters,

or tanks.

� Battery-box covers must be ventilated, and the

area around the box must be vented to out-

side air.

� All battery boxes and cases must be constructed of

nonconductive, noncorroding materials.

� Batteries must be secured so that the fasteners can-

not come in contact with battery electrolyte.

� Everything within 12 inches of the battery must be

covered or in some way protected so that it’s com-

pletely nonconductive. This is to prevent any acci-

dental short circuit between the item and the

battery terminal.

An easy way to satisfy these standards is to installall batteries in a commercially made plastic batterybox such as the one shown in figure 5-5. Pre-madebattery boxes in a variety of sizes are available at anymarine supply store. Just remember to secure the boxwith the straps provided, and make sure that the bat-tery is well ventilated to outside air.

Battery Maintenance and TestingThere are several situations that can cause prema-ture battery failure, but the most common by far isowner neglect. The second most common cause of abattery cashing in its chips before its time is the mal-function of the charging system. However, I classifyeven this as owner neglect, because the conscientiousskipper should monitor this charging system closelyenough to catch a malfunction long before it can per-manently damage the battery. Other common causes

of premature battery burial are using the wrong typeof battery for a given application, such as a deep-cycle battery where a cranking battery is needed andvice versa; and using batteries that are too small forthe task at hand. (The information on selecting bat-teries at the beginning of this chapter should havecorrected any problems you may have had in thoseareas.) And then there are the boatowners who chuckout perfectly good batteries they have convincedthemselves are bad.

I’ve seen more batteries unnecessarily replacedthan any other systems component I can think of. Itseems that many otherwise sane people blame the bat-tery for everything from an autopilot that doesn’t workproperly to warm beer. They will throw away a healthybattery without a thought to the more probable causesof their troubles. Just because your engine is crankingover slowly or your cabin lights are getting dim doesn’tmean you need a new battery. With the retail price of asmall marine battery bouncing around $100, I thinkit’s worth checking the old one to make sure if you re-ally need to replace it before you discard it.

As battery technology and construction meth-ods have improved over the years, maintenance hasgotten a lot easier. The biggest problems we used tohave were keeping the terminals clean and toppingup the cells with distilled water. These tasks are stillnecessary with the new versions of wet-cell batteries,but the new technologies have greatly reduced theconstant need to add water.

Fig. 5-5. Typical plastic battery box.

75


Battery case construction has reached new highsalso. Posts and case tops seem to remain sealed muchlonger than before, so electrolyte leakage and the re-sultant corrosion are not as important as they were.I’m still going to insist that you regularly check elec-trolyte levels and terminal integrity, though. A faultycharging system can literally boil the electrolyte outof the cells, damaging the battery and creating dan-gerous hydrogen gas, and it can do this in a veryshort period of time!

As you’ll remember from the basics covered ear-lier in this book, loose or corroded connectionscause excessive resistance, and that causes heat.When a high current is drawn from a battery, suchas when you start your engine, a loose corrodedconnection can generate enough heat to actuallymelt the plastic casing of the battery around the ter-minal stud. This opens the door for an electrolyteleak at the terminal that further compounds yourproblems.

The following maintenance checklist will go along way toward keeping battery problems at bay,and I recommend doing at least the visual part ofthese checks once every week, especially if you’rehooked up to a shore-power charger.

� Keep the tops of your batteries clean and dry. Use

a little warm water on a rag to wipe away any ac-

cumulated dirt and grime. A mixture of baking

soda and warm water is excellent for cleaning dirty

or corroded batteries. Don’t overdo the

baking soda, though. If it leaks through the caps

or vent holes into a cell, it will neutralize the acid in

the cell and destroy it.

� Check cables and connections for integrity and

tightness. At any sign of corrosion, remove the ca-

bles and use a wire brush or dedicated terminal-

cleaner brush to clean the post and the cable

connector. Terminal cleaning is shown in figures5-6 and 5-7. Don’t cheat and think that you have

done anything constructive by cleaning the exte-

rior of the cable-end terminal and post. The elec-

trical contact is made on the inside of the

terminal—that’s what counts. If your battery has

stud-type terminals, as many marine batteries do,

the cleaning tool will have to be helped a little

with coarse sandpaper or with a wire brush or

pocketknife. The socket on the terminal tool just

isn’t deep enough to clean the entire length of a

studded terminal.

� Top up the battery with distilled water. If you

can’t get distilled water, at least use low-mineral

tap water. There is a considerable variation in the

mineral content of tap water from one municipal-

ity to the next. Some tap water with low mineral

Figs. 5-6, 5-7. Steps to cleaning the battery post and clamp, using a battery service brush. Use these tools until you see shinysurfaces on both the post and inside the clamp. Figure 5-6 shows the terminal being cleaned; figure 5-7 shows the battery postbeing cleaned.

76


content (soft water) is fine for batteries; some is

terrible. The best bet is to check with a local battery

shop and ask about their experience with the local

water.

� Keep tabs on both your engine’s alternator and your

boat’s 110-volt battery charger, if you have one.

Overcharging or undercharging is damaging to any

battery. Overcharging will boil the electrolyte and

rattle the lead off the plates. Undercharging will al-

low the lead sulfate to permanently harden, reduc-

ing the surface area of the plates. A sulfated battery

will not develop full power and will eventually have

to be replaced.

Battery InstallationsThere are a number of ways to hook up and com-bine batteries. For the small, open boat, the choicesare fairly simple and easy to understand. But, if yourboat is a medium-sized cruiser with twin engines andboth a bank of starting batteries (for starting the en-gines) and a bank of house batteries (for supplyingyour needs while away from the dock), the batterysystems can get fairly complex. I will only attempt topresent the most common systems here.

First, refresh your memory on series and parallelwiring hookups as we discussed back in chapter 1.These two methods of connecting battery cells andbatteries are the primary methods builders use toalter system voltage and amp-hour capacity. Also,you need to know a little more about battery charac-teristics. To create a 12-volt lead-acid battery, man-ufacturers connect a series of six cells, which eachproduce a little more than 2 volts, to attain the 12volts in batteries used by most boats. Larger boatsmight use 24-volt systems, and some boats even usea combination 12- and 24-volt system, but these arejust 12-volt batteries connected in series to get thehigher voltage.

When battery cells are connected in series, thevoltage is multiplied. Thus, multiplying the numberof cells in a lead-acid battery by two gives the finalsystem voltage. If we hook these cells or batteries upin parallel, the voltage stays the same, but the am-perage of the system is multiplied. Thus, if you have

two 6-volt batteries with 25 amps each, wired in se-ries, you’ll end up with a 12-volt bank having 25amps of current available. If you wire these same twobatteries in parallel, you’ll have a 6-volt system with50 amps of current available.

The majority of recreational boats today oper-ate on 12-volt battery systems, so we’ll stick withthose. Figure 5-8 shows two pairs of 12-volt batter-ies. One pair is connected in series, the other in par-allel, and the resulting amperage and voltage of eacharrangement is shown. This is very important. I’veseen more than one boater trying to connect bat-teries in the spring, and they just can’t rememberhow they were attached when they took them out.

Here’s a quick tip to prevent this confusion: Sim-ply mark the cables when you remove your batteriesin the fall so you’ll remember how they go whenyou’re ready for your spring launch. Remember thatconnecting 24 volts to a 12-volt system can be a veryinteresting but very expensive mistake. The parallelhookup is not what you’ll find on your boat, as a bat-

SeriesBatteries

ParallelBatteries

Fig. 5-8. Two 12-volt battery pairs, one in series, one in par-allel. Remember that series connections combine the voltagesof the batteries connected; parallel connections combine theavailable amperage but do not change the voltage.

77


tery switch will usually separate the batteries (unless,of course, you’re building a large battery bank frommultiple batteries). I am just trying to illustrate whathappens to amperage and voltage in these circuits.

Battery-System ComponentsBesides the batteries, other components found in anybattery system are as follows: Every system will havecabling connecting the batteries to each other and tothe distribution panel and starter. There will be amaster control switch of some type to separate andisolate the individual batteries. In some cases a diode-type battery isolator is used to prevent batteries dis-charging into each other. And in some of the newerinstallations, a device called a battery combiner will beused to do the same thing. Naturally, all of these cir-cuit components must be rated for the amperage theyare expected to carry. Let’s go through this list andtake a look at each component.

Battery CablesIn the latest version of the ABYC battery standard, E-10, a major wording change has altered the re-quirements for cabling attached to battery terminals.It now states: “10.8.3. Battery cables and other con-ductors size 6 AWG (13.3 mm2) and larger shall notbe connected to the battery with wing nuts. 10.8.4.Multiple conductors connected to a battery shall beinstalled with the highest ampacity conductor ter-minal closest to the battery, followed by successivelysmaller ampacity conductor terminals. 10.8.4.1. Amaximum of four conductor terminals shall be per-mitted to be installed on a single battery stud. 10.8.5.Flat washers, if used, shall only be installed immedi-ately under the split lock washer and nut of the at-tachment stud.” This whole matter of the wing-nutattachment has been a bit contentious for years.These wing nuts do have a tendency to loosen andthis will cause the terminal connector to heat up ex-cessively due to the inherent resistance that is cre-ated. This represents a fire hazard on board!

Battery cables are the extremely heavy wires thatconnect your batteries to each other and to your dis-tribution panel and starter motor. They might also beused to connect other high-amperage equipment

such as generators, anchor winches, and large invert-ers. The battery cables are by far the largest wiresyou’ll find in your boat. They are also among themost important and the most neglected. Mostmedium-sized and larger boats will use a variety ofsizes of cables in the battery system. A mediumcruiser, for example, might have AWG 00 cables thediameter of your thumb between the individual bat-teries and AWG 2 cables connecting the batteries tothe boat’s systems. (In general, conductors largerthan AWG 8 are called cables instead of wires, and thewire-end fittings are called lugs instead of terminals.)

Battery cables, as with any other wiring on boardyour boat, must be large enough to carry the currentthat the equipment connected to them will need. Thesize of battery cables is based on the maximum am-perage that the starter motor and other high-demandequipment needs. Manufacturers generally do a goodjob of providing information on cable sizes in theirworkshop manuals.

The table below shows minimum AWG cablesizes required for various installations. When usingthis chart to select cable sizes, the positive and nega-tive cables must be the same size. Typically, the gaugeof the wire will be embossed on the insulation foreasy identification.

Battery Selector SwitchesWe have already established the need of larger boats,those much bigger than an open runabout, for a

Battery Cable Recommendations

AWG Gauge andCable Length . . . . . . . . . . . . . .Metric Equivalent

Up to 31⁄2 feet (1.1 m) . . . . . . . . . . . . . . . . . .4 (25 mm2)31⁄2–6 feet (1.1–1.8 m) . . . . . . . . . . . . . . . .2 (35 mm2)6–71⁄2 feet (1.8–2.3 m) . . . . . . . . . . . . . . . .1 (50 mm2)71⁄2–91⁄2 feet (2.3–2.9 m) . . . . . . . . . . . . . . .0 (50 mm2)91⁄2–12 feet (2.9–3.7 m) . . . . . . . . . . . . . .00 (70 mm2)12–15 feet (3.7–4.6 m) . . . . . . . . . . . . . .000 (95 mm2)15–19 feet (4.6–5.8 m) . . . . . . . . . . . .0000 (120 mm2)

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combination of cranking batteries to start the engineand deep-cycle batteries to run the boat’s systems.The longevity of these batteries will be greatly de-creased if they are used for the wrong application, soyou need a means to select which battery is in use atthe appropriate time. The very best way to do this iswith a battery selector switch with the familiar “off,”“No. 1,” “No. 2,” and “both” switch positions.

These switches should be installed on any boatwith an electric system, even if you have only a singlebattery. Of course, a single-battery installation doesn’tneed the four-position switch. A simple two-positionon-off switch will do fine. The ABYC recommenda-tions exclude boats using batteries smaller than 800CCA from the requirement for a battery isolationswitch, so if you buy one of these smaller boats, you’llprobably have to install the switch yourself. Fortu-nately, it’s an easy and straightforward job.

A recent experience I had brought home the im-portance of being able to quickly shut down anyboat’s electrical system in case of emergency. I wasmotoring across the bay when I noticed a small boatwith smoke billowing out from under the port-sidedeck into the cockpit. I immediately altered course toinvestigate and found a fellow who was, along withhis entire family, in a complete panic. The fire hadbeen started by a severe short circuit, and the boathad no means of shutting off the electrical system.Current from the battery was feeding the fire, makingit impossible to extinguish as long as the battery re-mained connected. There was no master switch ofany kind. It was an all-too-typical situation of a singlebattery installed on a small outboard-powered boat. Ijumped aboard the runabout and cut the positivebattery cable with a cable cutter I keep on board forworking with heavy shark leaders. The boat did havea working fire extinguisher aboard, and once the bat-tery was disconnected we were able to extinguish theblaze in time to save the boat. Even so, I’m not sureif this fellow’s family will ever again go boating withhim on any kind of boat.

This little melodrama points out how importantit is to be able to disconnect the battery power whenthere is an electrical fire. It’s imperative to disconnectthe power before you attempt to put out the fire. Aslong as there is battery current available, your at-

tempts to stop the fire will be futile. A $40 switchcould have saved this fellow hundreds of dollars indamage and made his family feel a whole lot better.

Some Typical Selector SwitchesLet’s look at some typical battery selector switches andlearn how to deal with them. My purpose here is notto attempt to show you every possible arrangement ofbatteries and selector switches, but to give you a goodunderstanding of the key elements in some of themost popular circuits. Modification of these basic sys-tems into more complex designs should not be toodifficult once you understand the basic circuits.

The Guest Co., a major supplier of battery switchesand components (now part of Marino), has some ex-cellent diagrams available that could be quite helpfulif you do decide to undertake a major system upgradeon your boat. Some examples of these diagrams followin this chapter.

Battery selector switches have a continuous andan intermittent (sometimes called momentary) ratingfor amperage. The continuous rating is the amperagethe switch can sustain while the switch is in normaluse. The intermittent rating is the much higher am-perage that a switch can sustain over a short period oftime, usually measured in seconds. It’s important toknow what these ratings are when you purchaseswitches for replacement of existing switches or foradditions to your system. You can’t tell much by sim-ply looking at the switch.

The battery switch you select must be capable ofhandling the extreme intermittent current associatedwith engine cranking and the maximum continuouscurrent of the electrical loads in your system. Ratingnumbers look something like 230 amps continuousand 345 amps intermittent. Heavy-duty switches of-ten have ratings of 360 amps continuous and 600amps intermittent. Be certain that the switch you pur-chase is intended specifically for battery switching.

Battery switches available today have an impor-tant feature known as make before break. Whenswitching from one battery to another, the contactinside the switch connects the battery you’re selectingbefore it disconnects the battery you’re deselecting.Without this feature your alternator could be de-stroyed in an instant. An alternator cannot stand

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even a momentary disconnect from the battery it ischarging without damage. Therefore, never shut yourbattery switch off with your engine running. An alternator is essentially a dumb device. Without theload of a battery on it while it’s running, it will auto-matically surge to its full output, burning out thediodes inside it.

Maintaining battery switches is not somethingmany people think of, but the most common causefor failure of these switches is loose connections onthe back of the switch. These loose connectionscause resistance, which in turn causes heat. Withstarter-motor current trying to get through the looseconnection, that heat is often enough to actuallymelt the plastic housing around the cable studs. Thiseffectively loosens the stud in the case and destroysthe switch. The answer here is to occasionally checkthe tightness of the connections at the back of theswitch. In fact, some switch manufacturers even rec-ommend using a specialized torque wrench to en-sure proper tightness!

Battery IsolatorsThe next commonly found component in multiplebattery systems is the battery isolator. By using theseisolators correctly, we can eliminate the problem ofbatteries discharging into each other. Isolators useheavy-duty diodes, which only allow electrical flow inone direction, to separate batteries, preventing onefrom discharging into the other.

It’s important to separate batteries for several rea-sons. First, one of the characteristics of batteries is thata fully charged battery will try to recharge its weakerbrother in a system. So, if you have a two-battery sys-tem and one battery is discharged with the batteryswitch left on “both,” the first battery will dischargeinto the second one until they reach the same volt-age. The ideal system will prevent this, but it involvesinstalling a battery isolator.

Battery isolators use a group of diodes, which areelectrical check valves that allow electricity to flowin only one direction. Isolators are installed betweenthe batteries on a system to prevent a charged bat-tery from trying to recharge a discharged battery towhich it’s connected. Isolators are an excellent addi-

tion to any low-end multiple battery installation. Figure 5-9 shows a typical 70-amp, two-batteryisolator.

Isolators need a little care, just like the other partsof your battery system. Isolators are rated to carry amaximum amount of amperage, so you need to se-lect the correct unit for your boat’s system. Standard

StarterMotorSolenoid

Parallel Batteries

IsolatorAlternator

BatterySwitch

Fig. 5-9. Typical battery isolator.

Fig. 5-10. Typical two-battery installation with isolator in-stalled.

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ratings are 70, 130, and 160 amps. The rating you useshould be, at a minimum, equal to your engine alternator’s maximum output capacity. Check themanual for your boat’s engine to get this specification.Isolators are also configured to be used with eithertwo- or three-battery systems, so make sure you havethe correct one for your system before you install it.

Figure 5-10 shows a typical two-battery systemwith an isolator installed. The current flowing throughthe circuit shows the isolator effectively separatingthe two batteries so that one cannot discharge intothe other.

Isolators have several faults that you need to beaware of before you buy one. First, the diodes used inthem are electrically expensive. The big diodes havean inherent voltage drop of around 0.7 volt or almost6 percent of the system voltage; this means that charg-ing times will be just that much longer. The second

problem with isolators is heat. All diodes produceheat—it’s where that 0.7 volt goes—and isolators aremounted on a substantial heat sink to dissipate thatheat. This means that the isolator needs to be wellventilated, or heat buildup in the heat sink will de-stroy the diodes. The third problem is that on someisolators the heat sink is a part of the circuit and theentire thing is hot when the battery is being charged.This type of isolator must be mounted where there isno chance of any conductive material coming in con-tact with it, because otherwise an unfused direct shortcircuit can result. In spite of these faults, an isolatormay be your best bet as an inexpensive way to keepyour batteries from discharging into each other.

Testing Battery IsolatorsTesting battery isolators to determine if they arefunctional is a straightforward matter. First markand disconnect the cables connected to the isolator.

2

3 4

1

Fig. 5-11. The four steps to test a battery isolator.

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Set your multimeter to the diode-check functionand test for continuity in one direction through eachdiode and no continuity in the opposite direction.Figure 5-11 shows the four steps required to test atypical isolator connected to one alternator and twobatteries.

If you discover that you have continuity in bothdirections for any of the diodes in the isolator, orno continuity in either direction on any of thediodes, the isolator must be replaced. Repairs are notpractical in the field. Also, alternators described asone-wire alternators won’t work with battery isola-tors without internal modifications to the alterna-tor that must be done in a professional shop.One-wire alternators have been widely used by bothMerCruiser and OMC.

Figures 5-12, 5-13, and 5-14 show three typicalmultiple battery installations using the componentsdescribed above. Figure 5-12 shows a typical single-engine, two-battery setup with a master switch and

SolenoidStarter Motor

Parallel Batteries

BatterySwitch

Alternator

Ground Stud on Engine

Parallel Batteries

Isolator

AlternatorEngine #1

AlternatorEngine #2

Fig. 5 - 14 Parallel Batteries

Isolator

AlternatorEngine #1

AlternatorEngine #2

ON

OFF

BatterySwitch

BatterySwitch

ON

OFF

Fig. 5-12. Single-engine, two-battery circuit with batteryswitch installed. Remember that battery switches must bematched to the maximum expected amperage they need tohandle.

Fig. 5-13. Similar arrangement, with the addition of an isolator.

Fig. 5-14. Twin-engine installation with two batteryswitches and an isolator.

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no battery isolator. Figure 5-13 shows a similararrangement with the isolator. Figure 5-14 shows atwin-engine installation with dual battery switchesand an isolator.

Battery CombinersRelative newcomers to battery interconnectivity aredevices known as battery combiners. These devices,available from all major marine equipment vendors,offer significant advantages over diode-type batteryisolators. Unlike conventional isolators, combinersdon’t suffer from the inherent voltage drop causedby diodes, which results in more precise batterycharging control. These new combiners incorporatevoltage-sensing circuitry that automatically connectsor disconnects multiple batteries (combined) basedon whether they are charging or discharging. You canthink of these combiners as electronic devices withsome built-in intelligence. Diode isolators do nothave such intelligence, which requires you to makesome compromises, especially when you are combin-ing different kinds of batteries, such as a cranking bat-tery and a deep-cycle battery. Cranking batteriesrecharge much more quickly than deep-cycle batter-ies. In the old days, this meant that when combiningbatteries, cranking batteries were typically over-charged while deep-cycle batteries continued tocharge. The Blue Sea unit shown in figure 5-15a over-

comes that problem by just turning off the charge tothe cranking battery in the circuit once the batteryreaches a prescribed voltage level. Additionally, thenew combiners allow temporary isolation of houseloads from the engine circuit during engine crankingto protect sensitive electronics. So there is no more“blinking out” of electronic gear during engine start-ing, when the whole system used to experience somuch voltage drop that many electronic devicescouldn’t function normally.

Testing Your BatteriesEven with proper maintenance, all batteries wear outeventually. The trick is to know when replacement is re-ally required. In my 35 years of experience dealing withstorage batteries, I’d say that they are the most frequentlymisdiagnosed component in any electrical system. Peo-ple assume that because their engine is turning overmore slowly than usual, the battery is at fault and it needsreplacement. More often than not, the battery is not theculprit, but rather a loose or poor connection, or perhapsa fault with the charging system. Before you can makeany real determination of the condition of your batteryor begin any other serious testing, you must first testyour battery. You need to recharge your battery first,then check the battery’s load-handling capability.

Figs. 5-15a, b. The Blue Sea System battery combiner.

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Hydrometer TestSo, what are these tests and what do they mean? Let’sstart with the hydrometer test. Hydrometers are usedto measure the specific gravity, the ratio of one liquiddensity against another. You’re likely to encountertwo and possibly three types of hydrometers used tocheck battery electrolyte condition, antifreezestrength, and diesel-fuel quality. These hydrometersare all different and cannot be interchanged, and theyare designed and calibrated against a standard for theliquid you’re checking.

A battery hydrometer is used to check the stateof charge for each cell of a wet-cell battery. This testcan only be performed on batteries that have remov-able cell caps—not gel-cells, AGMs, or sealed no-maintenance batteries.

Do you remember when I explained how a bat-tery works? I described a chemical reaction where theacid is absorbed into the battery plates, leaving onlywater. The hydrometer measures the change of theelectrolyte from acid to water and tells us the per-cent of charge of each cell in the battery. Knowing thepercent of charge does not tell you whether or notyou need a new battery. If all the cells are equally low,something is either discharging the battery or youhave a charging-system problem. The only other pos-sibility is that there are one or two bad cells, and thebattery has discharged the good cells into the badcells, equalizing the hydrometer readings.

You’re looking for a different reading betweencells. If all the cells are equally low, recharge the bat-tery and recheck the specific gravity for any varia-tion between cells. One low cell after rechargingindicates a battery on its way out.

Three very important points must be made re-garding specific-gravity testing:

1. Don’t attempt the test immediately afteradding water to a cell.

2. Don’t test immediately after charging.

3. Do test only after the electrolyte mixes and thebattery stabilizes.

This stabilization may take an hour or so, or youcan bring down what is known as the static charge byputting a load on the battery for about 15 secondsafter the recharge to stabilize the battery. It’s still bet-

ter to wait a while, but loading the battery will give aquick stabilization. Remember that the variation be-tween cells is more important than the actual maxi-mum specific gravity reading.

Most quality hydrometers have a built-in ther-mometer, and it’s not there to tell you it’s time to goto the beach. Specific gravity is calibrated at 80°F.To compensate for readings above or below this tem-perature, add or subtract 4 points for each 10° yourreading is below or above 80°. This compensationcan make the difference between condemning yourbattery or hanging onto it for another season. Maxi-mum specific gravity readings for electrolyte from acharged battery will range from 1.260 to 1.280, ascompared to pure water with a specific gravity of1.000.

At a hydrometer reading of 1.260, the electrolyte

Fig. 5-16. Temperature-compensated hydrometer in use.

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is 0.260 times as heavy as water because of the sul-furic acid in the solution. As the battery discharges,the acid leaves the water and goes into the plates inthe cell, and the specific gravity moves closer to1.000. A specific gravity reading that shows a 50-point difference between any two cells after re-charge and stabilization indicates that your batteryneeds replacement.

Figure 5-16 shows a hydrometer in use. Experi-ment a little if you’re going to use this method ofchecking your batteries.

Always wear safety goggles when working aroundbatteries. Hold the hydrometer in an upright posi-tion and draw in just enough electrolyte to float thebulb—no more or less. Too much electrolyte in thehydrometer tops out the bulb and gives you a falsehigh reading. When not enough electrolyte is drawninto the hydrometer, the bulb float indicates a badcell that’s really good. Carefully squeeze the elec-trolyte back into each cell as you check and recordeach cell’s reading. When you have taken a readingfrom each cell, wipe away any electrolyte drips fromthe battery top and throw out the rag.

Open-Circuit Voltage TestThe newer sealed batteries cannot be checked with ahydrometer, but you can still test the specific gravityon these batteries. You can’t compare individual cellswithin a sealed battery, because you don’t have a wayto get into them. However, this test is still a good wayto evaluate the overall state of charge of a sealed bat-tery. If you have a digital voltmeter built into yourboat’s instrumentation, you can continually moni-tor the state of charge.

This test is called the open-circuit voltage test. Ifyou don’t have a built-in meter, you can use yourmultimeter and take a reading right at the batteryterminals.

Figure 5-17 shows the voltmeter connected to abattery for an open-circuit voltage test. Be sure all ac-cessories are turned off when performing this test;otherwise you’ll get a low reading.

There is a direct relationship between specificgravity and a battery’s open-circuit voltage. You needa digital voltmeter for this test, as the accuracy

required is difficult to read on an analog unit. As withthe hydrometer test, the battery must be stable. Aheavy load or a recharge just before doing this test willgive you a totally inaccurate reading. Let the batterysit for an hour or so before the test, and your multi-meter will give you a meaningful reading. Use a digi-tal voltmeter hooked up as shown in figure 5-17, andcompare the reading to the table at right; this will giveyou a good indication of your battery’s state of charge.

Load TestThe load test tells you whether the battery hasenough amperage to back up the open-circuit voltage

Open-Circuit Voltage versus State of Charge/Specific GravityOpen-Circuit State of SpecificVoltage . . . . . . . .Charge (%) . . . . . . . . .Gravity

11.7 . . . . . . . . . . . . . . . . .0 . . . . . . . . . . . . . . . . .1.12012.0 . . . . . . . . . . . . . . . . .25 . . . . . . . . . . . . . . . .1.15512.2 . . . . . . . . . . . . . . . . .50 . . . . . . . . . . . . . . . .1.19012.3 . . . . . . . . . . . . . . . . .75 . . . . . . . . . . . . . . . .1.22512.6 or more . . . . . . . . . .100 . . . . . . . . . .1.260–1.280

Battery

Fig. 5-17. Voltmeter connected for an open-circuit voltagetest. This test will give you an indication of the battery’s stateof charge, but can’t tell you which cell within the battery isthe culprit.

85


reading you took above. Open-circuit voltage read-ings can be misleading and give you a false sense ofsecurity due to a phenomenon known as the surfacecharge. A battery in poor condition may give you areading as high as 12.5 volts or more if it has been sit-ting idle for a few hours. However, as soon as youtry to crank your engine with this battery, you’ll hearthat disheartening “click-click-click” sound that tellsyou there’s a battery problem. Load testing will giveyou some real answers about how your battery willperform when the chips are down.

An easy way to load-test your battery requires nospecial tools and is quite conclusive. Make sure allbattery-cable connections are clean and tight. Next,disable your engine’s ignition system, or, if you havea diesel engine, activate the fuel shutoff so the en-gine won’t start during the test. To disable the igni-tion system on a gasoline engine, follow theworkshop manual for the engine. On engines builtfrom about 1992, you should be able to disconnecteither a plug at the coil or distributor to disable theignition system. Do not try to disable the ignition byremoving the center high-tension lead on the coil;not only is this dangerous, but it could damage theignition system. (More on this in chapter 7.) Oncethe ignition or diesel engine shutoff has been dealtwith, hook up your voltmeter across the batteryyou’re testing, just as you did with the open-circuit voltage test. With the meter set to the DC voltsscale, crank the engine over for no more than about15 seconds. Carefully observe the meter’s lowest

reading in volts during the cranking. If it drops below9.6 volts, perform a three-minute charge test todetermine if the battery is worth saving. With elec-tronically fuel-injected engines, the minimum crank-ing voltage allowed is 10.5 volts.

Three-Minute Charge TestBegin the three-minute charge test by disconnectingthe battery’s ground cable to take the battery out ofthe boat’s circuitry. This will prevent any voltagespiking of precious electronic equipment you haveon board. Next, connect your multimeter set to mea-sure voltage across the battery terminals. Connect abattery charger with a quick-charge capability to thebattery. The charger should have 40 to 50 amps ofoutput, so it’s not your typical trickle-charger. Turnthe charger on to about 40 amps and maintain thischarge rate for three minutes while you observe yourvoltmeter. The battery is serviceable if the voltagereads less than 15.5 volts during the three minutes.Recharge the battery and redo the load test to be sureeverything is OK. If the battery reaches more than15.5 volts during this three-minute period, it’s timeto replace the battery.

After going through this series of tests, you’llknow for sure whether you need a new battery or not.It may sound like a lot of effort, but really, these testscan be performed in less than half an hour. I don’tknow about you, but I’d rather spend half an hourthan $75 to $400 for a new battery.

In the last chapter we went into some detail on thevarious types of marine batteries and how to main-tain and install them. However, the most crucialconcern of battery performance isn’t installation ormaintenance, although these two procedures arecertainly important enough, but in the method andextent to which they are recharged once they havebeen depleted to acceptable levels. A battery that’sregularly overcharged is going to shed material fromits plates and boil away its electrolyte, dooming itto a tragically short and ineffective life. A batterythat’s regularly undercharged is going to have itsplates choked with impenetrable and indestructiblelead sulfate and is likewise doomed to a prematuretrip to the local recycling station.

The three types of batteries we have discussed sofar—wet-cells, gel-cells, and AGMs—respond tocharging in different ways, but they are all very par-ticular about how they get their electrons reener-gized. Batteries must be recharged just so, and if youdon’t do it right, you as a boatowner are going to bemaking a lot more trips to the battery store than youneed to make. There are better things than new bat-teries on which to spend your boating dollars, so thischapter is dedicated to seeing that you get the max-imum life and performance out of your batteries byrecharging them properly.

There are many acceptable ways to recharge boatbatteries. Auxiliary generators, wind-driven genera-tors, solar panels, and water-driven generators are allused on boats in varying circumstances. However,the vast majority of us weekend powerboaters withsmall to medium-sized powerboats rely almost en-tirely on the engine-driven alternator and shore-powered battery chargers to keep our boat’s batteriesup to snuff. Thus, I am going to concentrate on thesetwo methods of recharging and leave the othersalone. I will, however, close this chapter by touchingon solar-powered means of keeping batteries toppedup and ready to go boating.

Alternator BasicsMany books that cover the subject of alternators gointo all types of alternator internal testing proce-dures and into details of how alternators actuallywork. I’m not going to do that in this book for justthe same reasons I didn’t go into great detail on bat-tery chemistry. It’s way too complicated to be cov-ered quickly, and it frankly isn’t very practicalinformation for the average boatowner. You want toknow how to tell if your alternator is working, and ifit isn’t, you need to know how to fix it. Everythingelse is excess baggage, so we are going to avoid it.

You should, however, be familiar with the basicunderlying principles of alternator operation—justenough to understand what is going on as your pre-cious batteries are being recharged. Before I gomuch further, here are some terms you need toknow that define components common to all alter-nator systems.

� Stator windings. These are the windings that

produce current inside the alternator. The stator is

the stationary part of the alternator inside which

the rotor rotates, which makes these two terms

easy to remember.

� Rotor. The rotor is the magnetized coil that spins

inside the stator windings. The coil on the rotor is

known as the field windings. (This is easy to re-

member because field is just a shortened form of

magnetic field.) The rotor provides the magnet-

ism that induces alternating current in the stator.

� Diode. A diode is an electronic check valve that

allows electrical current to flow in one direction

and blocks it from flowing in the other. Diodes

are mounted inside the alternator as part of a

bridge rectifier circuit.

� Bridge rectifier. This is the internal circuitry

that uses silicon diodes to convert alternating

Battery-Charging Systems

86

Chapter 6


current created in the stator windings to direct

current usable for recharging your batteries.

� Voltage regulator. This critical device adjusts

the current in the field windings to match your al-

ternator’s output and the needs of your batteries.

The voltage regulator also controls the output of

the alternator so that it doesn’t overcharge your

batteries.

Alternators work on the principle of induction(discussed in the Word about Inductive Pickupssidebar in chapter 3) whereby a magnet placed adja-cent to a wire will induce electrical current in thewire. Each stator winding in your alternator has avery long wire wound in a coil, and the rotor is apowerful electromagnet. By spinning the rotor insidethe stator, electrical current is induced in the stator,and by varying the amount of magnetism in the rotor(the primary function of the voltage regulator) theamount of electrical current produced by the statorcan be precisely controlled. Remember, all conduc-tors with electrical current flowing through them aresurrounded by a magnetic field. We can induce elec-tron flow in nearby conductors by rapid movementof this field in proximity to the conductors (thisworks in reverse as well, by moving a conductorrapidly in close proximity to a stationary magnet).

If the stator windings in your alternator (there areusually three) all had the same polarity (the positiveand negative terminals arranged the same way), youwouldn’t have an alternator, you would have a gen-erator producing direct current. However, alternatorshave their stator windings arranged in fingers so thatas the rotor rotates past the stator windings, the posi-tive and negative poles are constantly and rapidly re-versing, thus inducing alternating current. Becauseyour battery needs to be charged with direct current,this alternating current is passed through a bridge rec-tifier where it’s converted to usable direct current.

Why, you may well ask, do we go to all this trou-ble to generate alternating current, and then convertit back to direct current, when an old-fashioned gen-erator would develop direct current without all thecomplicated circuitry of the bridge rectifier? The an-swer is efficiency. An alternator can be built much

lighter than a generator, and it will produce muchhigher currents than a generator of the same size. It’sironic, but true: it’s easier and better to produce alter-nating current and convert it to direct current than itis to produce direct current straight from a generator.

Engine-Driven Marine AlternatorsThere are four broad categories of engine-drivencharging systems commonly found on boats today.The chances are better than good that your boat’scharging system will fall into one of the followinggroups.

1. Outboard engine with remote rectifier andno voltage regulator

2. Outboard engine with remote rectifier andvoltage regulator

3. Inboard or stern drive with remote voltageregulator

4. Inboard or stern drive with integral voltageregulator

Alternator ProblemsMost problems with alternators are best correctedby removing the alternator from the boat and takingit to an alternator shop, which has the special equip-ment needed to make delicate repairs. Some manu-facturers have factory exchange programs that allowyou to exchange your unit for an identical factory-rebuilt replacement—for a fee, of course. It’s a simplematter to pop the old alternator out, exchange it atthe dealer’s, then pop the new one back in. This ex-change is sometimes available no matter what con-dition your old alternator is in—a real blessing whenyou experience an engine fire or after your alterna-tor gets doused with salt water. Many offshore boatscarry a spare rebuilt alternator that can be substitutedfor a defective unit if it should give up the fight whilefishing the Gulf Stream or on a long weekend in theBahamas.

This swap-and-replace procedure presupposesthat you’re able to diagnose when and why the alter-nator in your system is acting up.

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Marine versus Automotive AlternatorsBefore one of your dockmate electrical “experts”(there’s one in every marina) tells you otherwise,remember that there is a big difference betweenmarine and automotive alternators. The brushesare sealed on ignition-protected marine alternatorsused on gasoline engines; this prevents dangeroussparks that could cause an explosion. (If you wantto see the difference, just open the hood of the fam-ily car in the dark while it’s running. You’re likelyto see sparks arcing inside the ventilation ports ofthe alternator.) Other differences between alterna-tors for cars and those forboats are that marine alter-nators are of heavier con-struction, may have a higheroutput, and have fewer cor-rosive parts than those forcars do. Don’t let anyonetalk you into substituting.This is an area mandated bythe USCG on gasoline-pow-ered vessels.

Those ventilation portsmentioned above also testifyto an alternator’s need forcooling air. That thing on thepulley that looks like a fan is,in fact, a fan. Often these fanshave blades that are set towork in one direction only,and the direction of enginerotation must be considered.If you have a twin-engineboat, the engines may rotatein opposite directions tocompensate for torque. Thealternators on twin-engineboats may not be inter-changeable without switch-ing the pulleys and fans.Straight fan blades on an al-ternator usually indicate thatthe unit will cool rotating ineither direction. If the blades

are offset, look for an arrow stamped on one of theblades that will show the direction of rotation, andalways check the manufacturer’s literature for exactinstallation instructions.

Alternator Electrical ConnectionsThe best bet for identifying the wires connected toyour alternator is to use your engine’s workshopmanual and wiring diagram. If, after testing your al-ternator, you discover that it must be removed foroverhaul or replacement, carefully mark all the wireswith tape. Also mark the terminal identification on

Early Prestolite StyleFits OMC

B +Output

B -Ground

Aux NotUsed

VoltageReg.

Green orYellow Field

RedIgnition

+

BlackGround

B -

Late Motorola/Prestolite Style Fits

MerCruiser & OMC

B +Output

AC Tap TachometerTerminal (Not Used)

(Exc) Purple orBlack Ignition +

(Sense) Red B+Battery + Sense

D +IndicatorLight (NotUsed)

Late Mando Style FitsMerCruiser and Others

B +BatteryOutput

P AC TAPTachometerTerminal

L2IndicatorLight

(EXC) Purple or BlackWire Ignition Terminal

S Red WireBattery + Sense

AlternatorThis plate has specification informationprinted on it that lists all of the detailsand specifications that are important toknow before installing this product. Thisplate has specification informationprinted on it that lists all of the detailsand specifications that are important toknow before installing this product

Late Motorola/PrestoliteStyle Fits U.S. Marine

B +BatteryOutput

AC TAP TachometerTerminal

D +Indicator

Light (EXC)Ignition

Purpleor BlackIgnition +

Delco Style fitsMercruiser & OMC

Red B +Battery + Sense

B +Output

B -Ground

Volvo/Paris Rhone FitsVolvo Penta

B +Output

Battery -Ground

D + or 61Indicator

Light

W TachometerTerminal

B +BatteryOutput

Delco Self Exciting StyleFits MerCruiser & OMC

B -Ground

Fig. 6-1. Seven common alternator backs, showing wiring connections.

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the back of the alternator to ensure that the wires goback where they should. Incorrectly reconnectingthese wires will render the new alternator inoperativeor burn it out. In the seven diagrams on page 88 infigure 6-1, alternators used by MerCruiser, OMC,Volvo Penta, and US Marine are shown with the ter-minals identified. You’ll need your engine’s servicemanual to match the wiring harness to these diagrams.

Charging-System SymptomsRegardless of the charging system used on your boat,the following symptoms usually indicate a problem:

1. Constant undercharging of the battery, indi-cated by poor battery performance.

2. Constant overcharging of the battery, indi-cated by having to add water, electrolyte accu-mulation on the top of the battery, or arotten-egg odor in the area of the battery.

3. Abnormally high or low voltage or amperagereadings from any meters installed in yoursystem when the engine is running.

4. A noisy alternator.

5. A constant whirring noise from radios or asudden reduction in signal strength with Lo-ran-C receivers.

Simple ChecksWhen you experience one of the above symptoms orwhen you otherwise suspect you have a charging-sys-tem problem, several preliminary checks should bemade before you assume the worst and replace youralternator.

Belt Tension and ReplacementFirst, check the belt that drives the alternator to seeif it’s too loose. Alternator drive belts, as shown infigure 6-2, should have no more than about 1⁄2 inchof deflection for each foot of span between pulleys.If the belt is loose, inspect it for excessive wear. Anyfraying of the belt’s edge, or cracks or grooving inthe belt, indicates that it’s time for a replacement.

When replacing an alternator belt, exactly matchthe new belt to the old one. Belt profile is just as im-portant as the length of the belt. There are differ-

ences in the V on various belts, as well as the actualbelt width at the outer edge. These dimensions mustbe correct so that the belt makes a tight fit into thepulley V to minimize slipping and to ensure longbelt life. Figure 6-3 on page 90 shows the correct pat-tern for a properly sized belt.

Make sure all the pulleys used by the alternatorbelt are aligned in the same plane. Any misalignmentwill rapidly wear away the belt and scatter blackresidue from the deteriorating belt all over the en-gine. Misalignment must be corrected to ensure longbelt life. Align the pulleys by shimming the alternatormounts until all are in perfect alignment.

Fig. 6-2. Checking belt deflection. This belt is adjusted justabout right!

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To replace an alternator belt, loosen the bolts in-dicated by the arrows in figure 6-4. Pivot the alterna-tor toward the engine, remove the old belt, and slidethe new one in place. Adjust to the correct tension—not tighter. Belts that are overtightened will wear outthe bearings that support the pulleys, such as those onthe alternator and water pump. Adjust the belt to thecorrect tension as determined by measuring the de-flection of the belt, then retighten the bolts. Recheckthe belt tension after about 10 hours of engine oper-ation, as the belt will have a tendency to wear andloosen. This is normal, but must be attended to.Newer boats are now coming through with “serpen-tine” belts (figure 6-5), familiar to the automotiveworld for several years now, and these promise to lastmuch longer than the conventional V-belt. In addi-tion, all of the systems using these belts have a self-ad-justing mechanism built into the pulley system.

With these belt-drive systems, it is extremely im-portant that all the belt-driven pulleys are in perfectfore-and-aft alignment. Any spacer shims used to ad-just the fore-and-aft position (such as an alternatormount pivot bolt) must be reinstalled after any com-ponent in the system is removed and replaced. Mis-aligned pulleys will cause the belt to “walk” off themonce the engine is running.

Fig. 6-4. Alternator mounting and adjustment bolts, typicallocations.

Fig. 6-3. Proper belt profile in the pulley.

Fig. 6-5. Serpentine belt.

AlternatorMounting Bolt

Alternator AdjustingMounting Bolt

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Engine-Mounted Circuit BreakersWhile you’re at it, check all the circuit breakers lo-cated on your engine. Each of these will have a littlered button with a number like 10, 25, 30, 40, 50, etc.stamped on the end. Figure 6-6 shows a typical circuit-breaker installation. One or more of these cir-cuit breakers might be associated with your chargingsystem and might have to be reset. Just rememberthat when a circuit breaker of any type is tripped,there is always a reason for it, and further testing willdetermine the cause. Check the entire system for cor-roded battery terminals, loose connections on thealternator, and perhaps a corroded plug on the har-ness that connects the engine wiring to the rest ofthe boat’s systems.

Engine GroundMake certain that the alternator is well grounded tothe engine. The alternator is sometimes groundedwith a short jumper lead from the alternator body tothe engine. It will be connected to a terminal marked

“GND” on the back of the alternator. Other times thealternator is grounded by an internal connection, somake sure all the mounting bolts are free from cor-rosion and tight. Also make sure that the engine’sground strap is secure.

The alternator is only grounded as well as the en-gine to which it’s bolted. Clean and tighten theground strap and mounting bolts as required, butdisconnect the battery first. If you short out any ofthe terminals with your wrench, you may createmore damage.

Testing the Charging CystemIf, after making all the preliminary checks listedabove, your problem still exists, it’s time for some in-depth investigation. Start at the heart of your charg-ing system, the battery. If the battery has failed, thebest charging system in the world isn’t going to fixit. So, the first step in checking out your charging sys-tem is to test the battery, as described in the last chap-ter. If the battery is up to snuff, you can test further tomake sure your charging system is OK.

For any of the tests described here, the batteriesshould not be fully charged, because any chargingsystem with a voltage regulator senses the batterycharge and adjusts the charge rate to the chargeneeded. Since a charged battery doesn’t need anymore charge, the voltage regulator will tell the alter-nator not to put out any current; it’s just not needed.All these tests require current from the alternator,and by discharging the battery a bit you ensure thatthere will be some.

To discharge the batteries, disable the ignitionsystem or diesel-injection system and crank the en-gine for 10 or 15 seconds several times. Allow sev-eral minutes between intervals for the starter to cooloff so you don’t damage the starter motor.

Never disconnect or reverse any battery cables oralternator leads with the engine running; damage tothe alternator diodes will occur instantly. When thebattery is disconnected, the voltage regulator seesthat the battery voltage has disappeared and tells thealternator to get to work. The alternator respondswith full output that can instantly shoot up to sev-eral hundred amps, and those internal diodes will

Fig. 6-6. Engine-mounted circuit breaker.

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explode just like so many kernels of popcorn in a hotpan. Exactly the same thing happens when the batterycables are accidentally reversed. If you aren’t planningon serving fried diodes for lunch, be very careful whenconnecting or disconnecting your battery cables.

Three Step Voltage TestNow you’re ready to hook up your multimeter anddo the three-step voltage test. This simple test is ef-fective on systems that have built-in voltage regula-tors not serviceable by the owner.

Turn off all the accessories on your boat, set yourmultimeter to read voltage, and connect the probesacross the battery terminals—red to positive (first)and black to negative. Make sure the battery masterswitch is turned to the battery on which you’re work-ing. Read and record the battery voltage. It shouldbe around 12.5 volts if you adequately discharged thebattery from full charge. This reading is called the ref-erence voltage—write it down somewhere handy.

Next, start your engine and run it up to a nor-mal mid-range operating rpm with all accessoriesturned off. Take and record your voltage at the bat-tery. This is the no-load voltage—and it should beno more than 2 to 2.5 volts higher than the refer-ence voltage. Write down the no-load voltage next tothe reference voltage.

With the engine running at the same rpm youused to check the no-load voltage, turn on all yourDC electrical accessories. Read your voltage at thebattery. This is the loaded voltage, and it should be atleast 0.5 volt above the reference voltage. Write itdown with the others.

If the no-load voltage is no more than 2.5 voltshigher than the reference voltage and the loaded volt-age is at least 0.5 volt more than the reference voltage,your alternator and regulator are operating correctly.

If the no-load voltage is above the 2- to 2.5-voltlimit, the battery is being overcharged and the voltageregulator is either defective or has a poor ground. Onalternators with internal regulators, remove the alter-nator and get it overhauled. If your engine has an ex-ternal regulator, use your ohmmeter to check forcontinuity between the regulator’s ground terminal(marked GND) and a good ground on your engine.

If the voltage readings are below the limits de-

scribed here, you’ll need to make one more check toensure that the alternator is getting field currentwhen the boat’s ignition key is turned on. Use thediagrams in figure 6-1 on page 88 to identify the ter-minal on the back of the alternator marked by eitheran F, EXC, or IGN. This terminal, which is suppliedignition voltage (hence the possible “IGN” marking)is where the excitation (supply of voltage) is sentthrough to the field (F) windings wound around thealternator’s rotor.

With your boat’s ignition key turned on, thereshould be a voltage reading very close to the referencevoltage at this terminal. If not, use your workshop man-ual to determine if the wire has a fuse in it, as it should.Replace the fuse if it’s blown and recheck for voltage.

If you still have no voltage reading, you couldhave a faulty ignition switch or bad wiring. Furtherinvestigation will be needed, but the charging sys-tem problem you were originally checking out is in

Fig. 6-7. Checking for field-excitation voltage at the alterna-tor. Remember, the ignition key must be switched on whenmaking this test. You should get a reading of approximately12 volts. The meter red lead is connected to the F terminaland the black lead to a good ground, in this case, the GNDterminal on this particular alternator. The key switch isn’ton yet, but a reading of about 12 volts will show on the me-ter if all is well.

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all probability not with the alternator but with thiswire. If you read battery voltage at the alternator,there is an internal problem with either the alternatoror possibly the regulator. Either way, these unitsmust be removed and sent to the specialty shop men-tioned earlier.

Figure 6-7 shows the field excitation voltage beingchecked. Remember, the boat’s ignition key must be inthe “on” position when checking for field voltage.

Charging Amperage TestVoltage is not your only concern when you’re check-ing alternator output. It’s possible that your alterna-tor amperage has diminished from its rating.Reduced amperage can be caused by a fault in the sta-tor windings inside the alternator (a rare occurrence)or by a fault in one or more of the alternator’s recti-fier diodes. Unless your boat is equipped with an am-meter (and most are not), you’ll need to test thecharging amperage with your multimeter. The in-ductive multimeter, such as the one I discussed inchapter 3, is the easiest to use for this test.

Clamp the inductive pickup of the meter over thelargest wire coming from the back of your alternator(the one on the terminal marked “B+”) and take an

amperage reading with the engine running at about50 percent of normal rpm and with all your DC ac-cessories turned on. As the alternator tries to keepup with this load, the ammeter should read verynearly the full output. If it doesn’t read full alterna-tor output, don’t be alarmed, as the reading will varydepending upon the number and extent of the loadsyou turned on. If you’re checking this system be-cause your battery has gone dead, and the readingyou get is much below about 35 to 40 percent of thealternator’s rated output, there may be a problem,and further testing is called for. Figure 6-8 shows theamperage test.

Two additional tests, the ripple-voltage test andthe draw test, are needed to confirm if an alternatorproblem exists or not. You can do one with your mul-timeter; the other will require a special LED test tool.

Ripple-Voltage TestThink of ripple voltage as a tiny amount of alternatingcurrent that has escaped past the bridge rectifier andhas imposed itself on the direct current charging yourbattery. A small amount of ripple current is normal,but if you find a significant amount it indicates aproblem with one or more or the alternator diodes.

Fig. 6-8. Using an inductive ammeter to check alternatoroutput. When checking amperage output in this fashion,turn on all your DC accessories and see if the alternator cankeep up to the demand.

Fig. 6-9. LED charging system tester, connected. Simple,two-wire connection; simply follow the instructions on thetester. Actron makes a similar tool for about $25.

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If you have one of the LED testers shown in figure6-9, alternator testing is a one-step procedure. Thetester has red and black leads and probes just likeyour multimeter. Attach the red probe to the B+ ter-minal at the back of the alternator and the blackprobe to a nearby ground (one of the alternatormounting bolts will do), and start the engine. Ob-serve the LEDs on the meter. Any lights flashing orconstantly lit indicate a problem with either the al-ternator or the voltage regulator (assuming the al-ternator is getting excitation voltage as describedearlier). Follow the instructions printed on the testerto determine what course of action is required. Fig-ure 6-9 shows the LED tester connected and readyto check a charging system. If you’re not sure whichterminal is B+ on your alternator, refer to figure 6-1.

If you don’t have the tester, you can do an alter-nating-current ripple test using your multimeter, asshown in figure 6-10. Connect your meter leads tothe battery with the red probe to the positive post and

the black probe to the negative post, and set it to theAC volt scale. Run the engine up to a fast idle, switchthe meter to the alternating-current volt scale, andcheck the reading. You should have no more than0.250 volt AC at the battery. If the reading you get isgreater than that, the diodes in your alternator are de-fective and the alternator must be serviced.

Draw TestThe last test I will mention is the draw test. Particu-larly in the marine environment, it’s possible to getelectrical crossovers from a hot wire to a nearbyground, causing a voltage leak that can drain yourbattery. Testing for crossover current is fairly sim-ple, but a few precautions need to be mentioned.

You’re looking for a constant electrical draw onyour battery. Make sure all the electrical accessorieson your boat are turned off and the engine is not run-ning. Make sure you have disconnected everythingincluding any radios and stereos with memories andclocks that bypass the switches. Next, disconnect thepositive terminal at the battery. Set your multimeterto read amps and connect it in series with the termi-nal end of the battery cable and the positive post onthe battery. A reading of any significant amperage(over 0.01 amp) indicates something on board isdraining your battery.

Now you must locate which circuit is the culprit.If your boat has fuses, isolate each circuit by remov-ing the circuit fuses one at a time and checking tosee if the amperage reading is eliminated or reduced.If you have circuit breakers, carefully turn off thebreaker switches one at a time until the amperagereading disappears or decreases to practically noth-ing. Once you have located the circuit that’s causingthe battery to be discharged, you should be able totroubleshoot the circuit just as I described above.

Outboard-Engine Charging SystemsOutboard-engine charging systems come in two vari-eties: with or without voltage regulators. The unreg-ulated systems have an alternator built into the top ofthe engine that puts out constant amperage of 5 or 6amps (or more on newer, bigger engines) any timethe engine is running. Regulated systems use a volt-

Fig. 6-10. AC ripple-voltage test. Your black meter leadshould be connected to a known good ground and the redlead to the B+ (output) lead on the back of your alternator.Remember to make sure that your meter is set to the AC volt scale.

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age regulator that’s similar to the one we discussedabove. However, there are enough important differ-ences to warrant a closer look.

Unregulated SystemsSmaller outboards from 6 to 10 horsepower usuallydo not have a voltage regulator. The charging systemson these small engines generally produce between 4and 6 amps of current at maximum output. Theproblem is that even this small amount of current canbe too much if the battery is charged and you aren’tusing any electrical equipment. This constant chargecreates a built-in overcharge that will boil away bat-tery electrolyte. If you have one of these small motors,it’s critical for normal battery life that you check andtop up the electrolyte frequently. You should neveruse anything but a wet-cell battery on these motors.

This nonregulated system consists of four majorcomponents plus the wiring that connects them all.On the top of the engine there are permanent mag-nets attached to the inside of the flywheel and a seriesof stator windings. When the engine is running, thepermanent magnets spin very close to the statorwindings and produce alternating current via mag-netic inductance, just as it’s produced in the inboardalternator discussed above. This alternating current isconverted into direct current that can be used tocharge the battery by passing it through a diode rec-tifier that’s slightly different than a bridge rectifier.

This rectifier is not contained in the same housingas the alternator, as are the ones found on inboard alternators. It’s really nothing more than a group ofdiodes mounted in a heat sink that’s bolted to the engine block. The heat sink provides a ground andhelps conduct the heat away from the diodes. Somemakers of outboards also install a fuse in the circuit,so check your owner’s manual.

The last component in this basic system is the battery.A common question regarding unregulated sys-

tems is whether they can be run without connectingthe motor to a battery, without damaging the stator-rectifier. The answer is that it depends. Some mo-tors can be run without batteries, and some can’t.Follow the recommendations in your owner’s man-ual. Some manufacturers provide caps to cover the

battery-cable terminals to prevent them from touch-ing while the engine is running without a battery.However, some companies, Mercury for example,also recommend disconnecting the stator wires fromthe rectifier and insulating them from each other ifyou’re going to use their motors without a battery.

Figure 6-11 illustrates a typical unregulated out-board charging system.

Testing the Unregulated SystemFrom years of experience, I can tell you that the boat-owner causes 99 percent of the problems that occurwith these unregulated charging systems. Rarely isthere any trouble with the permanent magnets or thestator windings under the flywheel. Problems are al-most always due to corroded or loose connectionsor to a failed rectifier. As I’ve mentioned before,diodes are very sensitive; they hate it when batterywires are crossed or grounded unexpectedly.

So, how do we verify the system is producingcharging voltage? It’s easy if you have one of the in-ductive ammeters described earlier: Simply clampthe meter over the positive battery cable with the en-gine running and rev the engine (don’t over-rev it).Most inductive meters work on a 100-amp scale, sodon’t expect to see much needle movement. Remem-

Stator windings

Rectifier Junction box

Battery

Fig. 6-11. Unregulated outboard charging system.

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ber, this is a very low-amperage charging system—4,maybe as many as 9 amps are all you can expect. Op-erate the engine at a fairly high rpm; if the needle onthe meter moves at all, your system is OK. If there isno movement, visually check all the electrical con-nections and terminals for corrosion and tightness.Clean and tighten them as needed.

If your system is equipped with a fuse, you shouldcheck it visually or test for continuity through thefilament with your ohmmeter. Check your engine’sowner’s manual for the location of the fuse if youhave one. If everything seems OK then the problem isprobably in the rectifier.

Testing rectifiers is tricky without the wiring dia-gram for your engine. They don’t all look alike, andthe wiring varies from one manufacturer to the next.The best approach for rectifier testing is to refer to yourengine’s service manual. All you’ll need for equipmentis your multimeter set to the diode-test scale.

If you test the rectifier and determine that it’s OK,you must next test the stator. These are all different,so work from your engine’s manual, and if you’reuncertain of the procedure, consult your local dealer.

Regulated Outboard SystemsLarger outboard engines (and, on the newest units,even the smaller ones) have voltage regulators in-stalled into the circuitry. Sometimes these are com-bination regulator-rectifiers like you might find onan inboard system. If a component is going to failin the system, it will most likely be this regulator-rectifier. The three-step voltage test described onpages 92–93 will work on these systems just like oninboard systems. It’s best to use your engine manualfor the tests necessary to isolate charging systemproblems in the regulator.

Shore-Power Battery Charging Systems and InstallationsPermanently installed battery chargers connected to your boat’s shore-power system fall into one of twogeneral categories. The most common is the ferro-resonant constant-output charger. The other is knowngenerically as a smart charger or three-step charger.

Many of the smart chargers available today also havea fourth stage known as an equalization stage and arethus four-step chargers. (More on that later.) A thirdpopular type of battery charger is really a combineddevice known as an inverter-charger that not only con-verts 12-volt direct current into 120-volt alternatingcurrent, but also incorporates a quality multistagebattery charger into one handy and compact unit.

As you’ll see in the following descriptions, the dif-ferences between the basic types of battery chargersare significant.

Ferro-Resonant Battery ChargersFerro-resonant battery chargers are deceptively sim-ple devices, nothing more than a simple transformer(a ferro-resonant transformer) that converts 120-voltalternating current into 12-volt alternating currentand a rectifier that converts the alternating currentinto direct current. The basic units, the simple house-hold battery chargers sold at the auto parts store,work just fine for getting the car started on a coldmorning or for a quick charge on a dead battery, butthey have no place on your boat.

Ferro-resonant chargers designed for use on boatsare a little more complex than the basic units. Theyincorporate some elaborate circuitry that will gradu-ally taper the charging current to roughly match thedemands of your battery. The better ferro-resonantchargers work fine on wet-cell batteries, but even thebest don’t do a very good job with the new gel-cell andAGM batteries. In fact, many of the problems associ-ated with premature battery failure, such as a rotten-egg odor and boiling of battery electrolyte (the resultof constant overcharging), are often caused by the useof the ferro-resonant chargers. Unfortunately, someof the largest producers of powerboats, such as Bay-liner and Sea Ray, still install ferro-resonant chargersin their boats because they are considerably less ex-pensive than newer smart chargers.

To determine which type of battery charger youhave, you’ll need to find the charger itself. It will bemounted somewhere near the batteries. If you don’tsee things like a battery-type selector switch or a temperature-compensation calibration switch some-where on the charger, you probably have the ferro-

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resonant type and should seriously consider an up-grade to a smart charger.

If you do have a ferro-resonant charger on yourboat, make sure that none of your batteries are gel-cells or AGMs. You must be able to check your batteryelectrolyte level regularly if you have a constant-ratecharger. The tendency, particularly for people whoplug into shore power and use their boats infre-quently, is to overcharge the batteries and boil out theelectrolyte. One trick used by many boatowners whohave this type of charger is to leave on a DC-poweredcabin light or two, even when they are away from theboat. This light puts a small drain on the batteries,minimizing the overcharging effect.

If you have a constant-rate charger, you shouldcheck all the cells in your batteries every two weeksor so and top them up with distilled water as needed.Batteries that run low on electrolyte will burn up inshort order. Figure 6-12 shows a typical constant-rate charger.

Smart ChargersThe newest wave of electronic battery chargers,generically called smart chargers, is a by-product ofpower-supply technology for computers. Smartchargers are small, reliable, and highly efficient.They are also extremely complex as compared to thesimple ferro-resonant chargers, and I won’t evenbegin to describe their circuitry. Suffice it to say thatthey charge your batteries in precise steps, or phases,that are highly beneficial to the longevity of yourbatteries. More important, these steps are adjustableto accommodate the type of battery you have, mak-ing them the only choice if you have gel-cell orAGM batteries.

These new smart chargers are produced by anumber of manufacturers and have really gone a longway toward maximizing the potential for the newestbattery technologies, both gelled and AGMs. How-ever, don’t for a minute assume that a smart chargerwill be a waste of money if you have standard wet-cellbatteries. All batteries will benefit from using a smartcharger. These chargers are available in a variety ofconfigurations for single-, dual-, and three-battery-bank installations and have amperage ranges from

as few as 8 amps to as many as 130 amps for thelargest inverter-charger combinations.

Phases of Battery ChargingUnlike the ferro-resonant chargers that gradually re-duce the charge rate along a rather steadily slopingcurve as a battery comes up to charge, smart charg-ers use three and sometimes four distinct phases forrevitalizing your batteries.

1. The bulk phase. The first phase of the battery-charging cycle is known as the bulk phase.This is where most of the charging occurs. Adischarged battery can accept a higher rateof charge, up to about 70 to 75 percent of thetotal charge, in the initial stages of chargingthan it can in the final stages. Typical chargerates during the bulk phase are 20 to 40

Fig. 6-12. A ferro-resonant charger. These constant-ratechargers have destroyed many a battery!

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percent of the battery’s capacity in ampereswith a voltage of about 14.4 volts. Gel-cellswill charge at about 14.1 volts. When the bat-tery is 75 percent charged, the smart chargerautomatically switches to the acceptancephase of the charge cycle.

2. The acceptance phase. The second phase of the battery-charging cycle is known as the accep-tance or absorption phase. During this phasethe voltage is maintained at 14.4 volts forwet-cell and AGM batteries and at 14.1 voltsfor a gel-cell. The charging amperage is grad-ually reduced until a rate of 4 percent of thebattery’s capacity is achieved. Thus the accep-tance phase for a 100-amp-hour battery endswhen the charging amperage the battery willaccept reduces to 4 amps. The smart chargerautomatically switches to the float phase.

3. The float phase. The final phase of a normalcharging cycle is known as the float or finishphase, during which the smart charger reducesthe voltage to 13.3 volts for wet-cells andAGMs and 13.7 volts for gel-cells. Gelled elec-trolyte batteries typically have a slightly higherfully charged open-circuit voltage than theirwet-cell brothers do.

The float phase is more maintenance thanan actual charge because it keeps the battery ata full charge without overcharging. This is thebig difference between the smart chargers andthe ferro-resonant units described earlier.

4. The equalization phase. The fourth phase of bat-tery charging I want to discuss is really an-other maintenance phase and is only used onwet-cell batteries. In fact, use of the equaliza-tion phase is quite damaging to gel-cells anda waste of time on AGM batteries.

The equalization phase takes care of minor irregu-larities in specific gravity between cells that develop as abattery ages. As your battery gets older, the chemical re-actions inside the individual cells can vary slightly withvariations in the chemicals in the water you’ve added tothe cells and with minor variations in the manufactur-ing tolerances of the battery. Lead-sulfate particles will

eventually begin to cling to and build up on your bat-tery’s cell plates. As this buildup continues, less and lessof the battery’s cell-plate area is exposed to the elec-trolyte and the cell’s capacity is effectively reduced.

The equalization phase minimizes this prema-ture buildup of lead sulfate by charging the batteryat amperage equal to 4 percent of capacity until thevoltage reaches somewhere between 15.5 and 16.2volts. This controlled overcharge literally rattles thesulfate particles out of the battery plate, forcing themback into the electrolyte where they belong.

The danger with using the equalization phase isthat you can do it too often. In some industrial ap-plications, equalization is used as a part of everycharge cycle because maximum battery “punch” isrequired. This is simply not the case on a powerboat,and you should equalize your batteries no more thanthree or four times per boating season.

Not all smart chargers offer an equalizationphase. On those that do, it’s not automatic and mustbe selected manually.

Temperature CompensationAll of the smart chargers I have worked with havesome form of temperature compensation built in tohelp the brain of the charger determine the propercharge rates. Three common arrangements are avail-able. One method requires the installer to select atemperature setting from a selector switch mountedon the charger housing. Another uses automatictemperature compensation with a built-in tempera-ture sensor on the charger. I feel that these two meth-ods, although certainly offering a technologicalquantum leap from the ferro-resonant chargers, arestill a bit lacking. The best sensing for temperaturecompensation can only be made at the battery itself.The temperature of the battery will change dramati-cally as it charges, whereas the temperature sur-rounding the charger itself may not if it’s mounted asit should be in a well-ventilated location.

The best chargers today use the third type of tem-perature compensation: a temperature sensor that’smounted to either the side of the battery or inside thebattery box. Always look for this feature when youupgrade your battery charger.

99


Testing Battery ChargersTesting your shore-powered battery charger to deter-mine if it’s functioning is easy. With the chargerturned off, do an open-circuit voltage test (as de-scribed in chapter 5) at the battery the charger is con-nected to. Turn the charger on and observe yourvoltage reading at the battery. If the charger is func-tioning, you’ll get a reading of at least 0.5 volt greaterthan the open-circuit voltage. If it’s not workingproperly, the charger may have a blown fuse. Thefuse is usually accessible on the outside case of thecharger and is easily changed.

One charger I’ve worked with, however (made byStatpower), locates the fuse inside the charger housing,necessitating partial disassembly of the unit to checkthe fuse. Check the manual for the charger on yourboat to determine the exact location of the fuse.

If the fuse checks out, you may have a problemwith the shore-power side of the circuit supplying thecharger. Remember: Alternating current can kill you!Before starting to troubleshoot the battery-chargercircuit, be sure to read chapter 11 of this book, andif you have any doubts about your ability, call in aprofessional marine electrician to help.

Figure 6-13 shows a state-of-the-art Xantrex mul-tiphase smart charger. It also has a manual gel-cell,

wet-cell, or AGM selection switch, a battery-mounted temperature sensor, and switching parame-ters for different phases.

Solar CellsSolar panels are increasingly being used on somecruising powerboats to supplement other onboardcharging systems. The silent energy that solar panelarrays provide is quite appealing to many boaters, andonce installed, solar panels are virtually maintenancefree. For boats that spend a lot of time at anchor awayfrom the dock, and not much time underway, the 50to 80 watts that medium-sized panels provide can bethe difference between keeping the batteries chargedup or running them down over time.

There are several important points to rememberabout solar panels. First, they do get hot sitting in thesun. If they get too hot, their output will actually de-crease. Several years ago, when I was testing solar pan-els for Cruising World, I discovered that at noon on aJuly day at 42° latitude, the panels were being heatedto 120°F, at which point their output began to dimin-ish. So when mounting panels on flat surfaces, youmust raise them above the surface to allow air to cir-culate on both sides of the panels.

Since a solar panel will allow a battery to dischargethrough the panel when the panel is not exposed to thesun, all panels must have a blocking diode in the posi-tive feed from the charger to the battery. The diode letscurrent flow from the panel to the battery but blockscurrent flow from the battery back through the panel.On most panels, the diode is in a small box mountedat the output terminals on the back of the panel.

Finally, no panel should be installed without acharge controller—a fancy term for a voltage regula-tor—since the 15 to 20 volts a solar panel can produceis too much for sealed, gel-cell, or AGM batteries.Some charge controllers have internal blocking diodes,however, and you don’t want redundant blockingdiodes since in marginal light situations the panel out-put could be reduced to a useless value (remember,diodes have an inherent 0.7 voltage drop throughthem). You can bypass or eliminate the blockingdiode on the panel if the charge controller has aninternal blocking diode.Fig. 6-13. Xantrex 40 amp charger.

Ignition-System ComponentsWhen people think of their boat’s electrical systemand its parts, they generally don’t think of the engineignition system as being a part of it. Well, if yourengine suddenly quits one day and you find that thefuel system is OK, then the most probable cause forthe shutdown will be a faulty ignition system, andyou’ll definitely be working with electrical compo-nents to correct the problem.

If your boat has a diesel engine, it neither has norneeds an ignition system, and you can skip thischapter, reveling in the luxury of never being trou-bled by overgapped spark plugs, out-of-control con-trol modules, or miswired ignition wires. However,if you own a small to medium-sized powerboat, thechances are very good that it’s powered by a gasolineengine replete with a complex assortment of igni-tion-system parts. All gasoline engines need an ignition system to light the sparks that fire the cylin-ders that turn the crank that spins the prop that getsus over the water to where we want to go.

Inboard gasoline-engine ignition systems allwork on the same simple principles. When youturn your starter switch, the ignition-control mod-ule or CDI unit senses your desire to start the en-gine. Electrical energy is drawn from a battery(usually) and sent to a coil where it’s transformedfrom a low voltage to a very high voltage. From thecoil, this high voltage is sent via heavy ignitionwires to the distributor where it’s directed throughthe distributor cap and additional ignition wiresto the individual spark plugs. Inside the spark plugthe voltage comes to a dead end where in a fit of in-tense frustration it leaps across a precisely cali-brated air space, creating the spark that ignites thefuel vapors in a cylinder of the engine. If severalhundred other engine parts are all doing their thingat precisely the right time, you’re on your way. Ifnot, it’s time to break out the oars or look for a

tow. Fortunately, such malfunctions are unusualbecause the modern ignition system is about as de-pendable as electromechanical contrivances canget. But they do, on occasion, fail, and when theydo, you’ll want to be able to identify and deal withthe problem. That’s what this chapter is about.

To maintain and troubleshoot your ignition sys-tem, you need a basic understanding of how itworks. Most people I talk with about marine elec-trical systems begin with the feeling that they reallyknow what’s going on with their ignition system.Then I probe a little and find that in most cases theyknow just enough to be dangerous. Quite oftenwhen there is an ignition-system failure, all the “ex-perts” on the dock come up with some interestingsuggestions for this or that. All of this free advice, inmy experience, adds up to the boatowner replacingperfectly good parts. Knowing how your systemworks will go a long way toward eliminating thisproblem.

Inboard Ignition-System ComponentsThe key ingredients in the recipe for this witch’sbrew of electronic and electrical apparatus thatmakes up your ignition system are as follows: onebattery, one control module, one distributor (withcap), several yards of ignition wire, and one sparkplug for each engine cylinder. Let’s take a brief butclose look at these ingredients one at a time. I willhave a lot more to say about all of these items later inthe chapter. Right now I just want you to know whatthey do.

Ignition-Control ModuleThe ignition-control module (called the capacitive-discharge ignition, or CDI unit, on PWCs and out-board engines; we’ll look at this in more detail laterin the chapter) is the little black box that coordinatesand controls all the various functions of the igni-tion system. It’s usually one or more computer

Maintaining Marine Ignition Systems

100

Chapter 7


chips, and when it malfunctions there is nothing todo but replace it with a new one. There are many dif-ferent designs of these modules, and no two enginebuilders use just the same one.

To be useful in an ignition system, the high volt-age produced in the secondary coil windings needs tobe continuously turned on and off as the engine runs.This ensures that each cylinder gets spark at exactlythe right time. With early ignition systems, beforeignition-control modules, breaker points acted as theswitch for the primary voltage. On today’s enginesthe ignition-control module does the switching, andit may have several other functions as well, depend-ing on the manufacturer.

Ignition CoilThe ignition coil uses the principle of magnetic in-duction to transform 12-volt battery voltage to the25,000 to 50,000 volts needed at the spark plugs. Theignition coil is nothing more than an electrical trans-former, a miniaturized version of the transformersyou see hanging from utility poles all over the world.Transformers use two coils wound around oppositesides of a doughnut-shaped iron core. Running 12-volt battery power through the first coil, called theprimary, or low-voltage side, induces up to 50,000volts of power in the second coil, called the secondary,or high-voltage side. As you already know from yourprevious reading, all wires that have electrical currentflowing through them are surrounded by a magneticfield.

The higher the current, the stronger the magnet-ism. If a very long, thin wire is coiled around a metal-lic core, the strength of the magnetism is increased. Ifa magnet is moved close to a coil of wire, electricalcurrent is induced in that coil of wire, just as with thealternator field windings discussed in chapter 6. By in-creasing the number of windings in the coil, we in-crease the amount of voltage. Conversely, if we reducethe number of windings, we reduce the voltage. Thisinduced voltage is how step-up and step-down trans-formers work. An ignition coil is really a step-uptransformer.

The primary side of the coil has a series of wind-ings that conduct battery voltage. The magnetic field

that’s created around the primary coil engulfs sec-ondary windings inside your coil. Because there area great many more windings in the secondary side ofthe coil than there are in the primary side, the voltagethat’s induced by the magnetic field is stepped up tothe high level needed by the spark plugs. By alteringthe number and ratio of windings in the primary andsecondary sides of the coil, engineers determine theexact voltage we will get from the secondary side ofthe coil.

DistributorWhen the very high secondary voltage leaves the coil,it goes to the distributor where it’s directed by the ro-tor inside to the correct cylinder at exactly the rightmoment to fire each spark plug. The rotor rotatesinside the distributor cap and directs secondary volt-age into the correct ignition wire and ultimately to

101


Rotor

DistributorControl Unit Switched by

Distributor

PrimaryWinding

Coil

PrimaryTerminal

Spark Plug

TriggerMechansm

ElectromagneticField

Low PrimaryVoltage

PrimaryTerminal

DistributorCap

High Secondary Voltage

Fig. 7-1a. Current flow through a typical electronic ignitionsystem. In this diagram the thicker lines indicate secondaryhigh-voltage conductors. Primary voltage is equivalent tobattery voltage and is indicated by the arrows, which alsoshow the direction of flow at the point indicated.

102


the spark plug for the cylinder that needs to be “litoff” at that time.

Figure 7-1a on page 101 illustrates the flow of cur-rent through a typical electronic ignition system, show-ing both the primary and secondary sides of the circuit.

Distributorless IgnitionIgnition systems on gas inboard engines have evolvedto a system that eliminates the distributor entirely.These systems, which are widely used in automotiveapplications, have been adopted by MerCruiser, Cru-sader, and others and are becoming the norm. Dis-tributorless ignition systems (DIS) offer some distinctadvantages, particularly the elimination of the distrib-utor, cap, and rotor, parts that require periodic main-tenance and inspection. A short list of the advantagesof a DIS is:

� No timing adjustments are needed; it’s done auto-

matically via the engine computer.

� No moving parts to wear.

� No distributor to accumulate moisture and cause

starting problems.

DIS also allow more precise timing and spark con-trol over the full spectrum of engine rpm, all con-trolled by a mini-computer. The primary componentsof this system are:

� Engine control module (computer).

� The ignition module, which is interfaced with the

engine module.

� A magnetic sensor, or triggering device, that is keyed

to either the engine flywheel or the engine camshaft

to sense piston position in the cylinders.

� High-tension coils to supply secondary level high

voltage to the spark plugs.

A DIS may have one coil per cylinder, or one coilfor a pair of cylinders. On paired systems, each end ofthe secondary windings of the ignition coil will be con-nected to a spark plug as shown in Figure 7-1b. Theseends are connected to cylinders that are opposite in theengine’s firing order, but both at top dead center(TDC) simultaneously. One plug will fire on the com-pression stroke and the other will fire simultaneouslyon the opposing cylinder’s exhaust stroke, referred to

Fig. 7-1b. A paired cylinder DIS.

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as “wasted” spark. It doesn’t really hurt anything, butit reduces the number of components required.

Employ the basic maintenance considerations asfor any ignition system. Keep coil towers and plugwires clean and free from any oily film that can attractdust and then moisture droplets (which will ultimatelycause high-voltage arcing and insulation damage onthe wiring and coil cases). If a problem does occur withone of the electronic components, specialized scantools are required to properly diagnose computer andignition modules.

To date, I’ve only had to replace the spark plug wiresabout every 750 to 1,000 hours of engine run time.Spark plugs last almost indefinitely with these systemsbut it’s best to remove the plugs seasonally for inspec-tion and to apply a light coat of antiseizing compoundto the threads. If you wait until the plugs actually wearout, you may find that they’ve rusted themselves inplace, making removal almost impossible.

Ignition WiresWhile the voltage coming from the secondary side ofthe coil is very high (up to 50,000 volts), the amperageis comparatively low. This means that the wires thattransmit this current from the center tower of the coilthrough the distributor and on to the spark plugsmust be of a very high quality and contain a very lowresistance. Cheap or deteriorated ignition wires areone of the primary causes of ignition-system failure.They can also cause maddening radio interferenceand a host of problems with other sensitive electricalequipment, not only on your boat but on the boat inthe next slip as well. It really pays to keep a sharp eyeon your ignition wires. When they start to look dete-riorated, they are deteriorated. Replace them.

Spark PlugsThe last and one of the most important parts of theignition system is the spark plug. It’s the spark plugsthat deliver the sparks to the cylinders, and thosesparks are the focus of the entire system. Spark plugscome in a bewildering variety of types and sizes.

Fortunately, your job as a boatowner is fairly sim-ple. The engine manufacturer will have precise spec-ifications on spark plugs, so all you have to do is keepthe plugs clean and properly gapped and replace

them when (or before) it becomes necessary. I’ll dis-cuss changing plugs later on.

Regulations Regarding Ignition SystemsI need to make several important points before con-tinuing much farther into this chapter. Most of theignition systems in use today employ solid-state de-vices for control. In some cases the best approach totroubleshooting will be to consult this book alongwith the workshop manual for your engine. You mayfind that the only way to be certain of a diagnosis is totry a new component. At that point it’s time to callin a pro, unless you’re quite experienced and havefull confidence in your mechanical ability. Whenthat’s the best bet, I’ll point it out in the text.

At the very least, after reading this chapter, you’llbe able to perform all routine maintenance on yourboat’s ignition system. When you do need to call amechanic, you’ll be able to intelligently talk aboutyour problem. Ignition-system components used onboats fall under the jurisdiction of the U.S. CoastGuard and must be manufactured in accordancewith their regulations. Use of ignition parts that donot comply with these rules and regulations could re-sult in a fire or explosion. Don’t even think aboutcheating on this by buying less-expensive automotivereplacement parts. These may look the same as themarine-grade parts; they are not.

The USCG mandates that ignition-protection re-quirements be met in the Code of Federal Regula-tions (CFR), so this is not a mere recommendationbut law. The bottom line on ignition service is thatno shortcuts are allowed. Follow the advice in thischapter, and you’ll be way ahead of the game.

Outboard and PWC Ignition SystemsUnlike those on inboard engines, most outboard andPWC ignition systems don’t use battery power tofeed the primary side of the ignition circuit. Withthese systems, voltage required for the primary sideof the circuit is generated under the engine’s fly-wheel, using the same principle of magnetic induc-

104


tion already discussed in chapters 3 and 6. The essen-tial difference is that these systems use a series of per-manent magnets located around the inside perimeterof the underside of the flywheel.

As the engine rotates, these magnets move pastcarefully placed coils of wire mounted on a timingplate, which is also located under the flywheel. Youguessed it: voltage is produced by induction in thesecoils. One coil acts to produce the primary voltage,which initially is much greater than with inboard sys-tems. Typical primary voltage is around 175 to 300volts alternating current. The coil producing thisvoltage is generally known as the charge coil, and itsends its current directly to the system’s ignitionmodule where it is converted to direct current via arectifier circuit built into the ignition module. Onceconverted, the current is stored in a capacitor (anelectrical device designed to temporarily store anelectrical charge), which is also built into the igni-tion module, for later delivery to the ignition coilfeeding a given cylinder. Unlike most inboard sys-tems, outboard engines use an individual coil foreach cylinder.

The second coil, also found under the engine’sflywheel, is known as the sensor, trigger, or pulsar coil,depending upon the engine manufacturer (we willuse trigger coil). This coil sends a much smaller volt-age, typically from 1 to 9 volts, to the same ignitionmodule as the charge coil where it triggers a transis-tor (a silicon-controlled rectifier, or SCR) matched toa cylinder. Once the SCR gets its cue, it triggers thecapacitor to release its stored charge and sends it tothe primary side of the ignition coil for the cylinderthat needs to be fired. A much higher voltage is sentto the primary side in outboards and PWCs than issent in the inboard-engine systems. The output of thesecondary side of any ignition coil is proportional tothe input on the primary side. By sending a muchhigher voltage into the primary side of the coil, we getthe same high output from a physically smaller pack-age than on inboard motors; this saves valuable spaceunder the outboard-engine cowl. These systems aregenerally referred to as capacitive-discharge ignition(CDI) systems, and we will take a closer look at themlater in this chapter.

Figure 7-2 shows the layout of a typical outboardengine CD ignition system. Figure 7-3 on page 104illustrates a typical PWC installation of this same type.

Maintaining Ignition SystemsMaintaining your boat’s ignition system is an easytask requiring just a little care and tidiness. Thebiggest enemies to your ignition system are the sameas those for any other part of your boat’s electricalsystem. It’s just that the consequence of impropermaintenance is more obvious in the ignition systembecause of the extremely high voltage found on thesecondary side of the system.

Corrosion ProtectionAll wiring connections and terminals need to beprotected against corrosion. On modern systems,sealed Deutsch plugs are the norm today, and theywork exceptionally well, requiring no maintenance.Their three-ribbed silicone-rubber sealing rings ef-fectively keep all moisture away from the electricalcontacts inside the assembly. Other systems using

CDIunit

Killswitch

Ignition coil

Pulsar coilCharge coil

Fig. 7-2

Fig. 7-2. Typical outboard engine ignition system. In this di-agram, the key components of a typical outboard-engine ca-pacitive-discharge ignition (CDI) system are noted, withtheir typical location shown.

1 2 3

4 5

6

9, 10

811

12

13

14

16

17

27

15

26

23, 24

25

21,2218 19

28 32 3329 30

36

35

20

31 34

Fig. 7-3

7

Fig. 7-3. Typical PWC capacitive-discharge ignition system: 1. Protective padding. 2. Cover plate. 3. Screw. 4. Wiring har-ness. 5. Hose guard. 6. Access plug. 7. Ignition system housing. 8. Bracket. 9. Lock washer. 10. Bolt. 11. Cap. 12. Spark plug.13. Cap. 14. Cables. 15. Ignition coil. 16. RPM Limiter. 17. Screw. 18. Wiring hold-down. 19. Screw. 20. Grommet. 21. Lockwasher. 22. Bolt. 23. Washer. 24. Screw. 25. CDI unit. 26. Harness sheathing. 27. Screw. 28. Stator plate. 29. Flywheel ring-gear. 30. Flywheel. 31. Woodruff key. 32. Lock washer. 33. Nut. 34. O-ring cover seal. 35. Screw. 36. Outer cover.

105


106


traditional ring-eye terminals and studs to connectcircuit components should, after assembly, besprayed with a corrosion inhibitor like Boeshield T-9.

Figure 7-4 shows a modern Deutsch plug with thesilicone-rubber sealing rings that make these plugs anexcellent choice for the marine environment.

Apply a coating of dielectric grease to the metalsurfaces of all spark-plug wires before they are pluggedin. Also, make sure the rubber boots on both ends ofthe plug wires are supple and are pushed down aroundthe towers on ignition coils and distributor caps as wellas over the spark plugs. Any heat-hardened or crackedboots must be replaced. The biggest cause of prob-lems with the ignition wires to the spark plugs is dam-age from chafe and exposure to exhaust-manifoldheat. These wires must be kept secure in the factory-supplied hold-down straps found on all engines. Fail-ure to do so will almost always result in problems likeengine misfiring and skipping.

System CleanlinessProbably the biggest cause of ignition-system failureon any engine is the accumulation of dirt and oil

film. Contrary to popular belief, spraying down thecoil, plug wires, and distributor cap with productslike CRC 6-56 or WD-40 to seal them from moistureis, in fact, one of the worst things you can do. Theoily film they leave behind is a magnet for dust anddirt, which attract moisture and condensation.

Moisture is a good conductor of electricity, andany weak points in the insulation on the secondaryside of your ignition system will provide a naturalpath to ground or between cylinder towers on dis-tributor caps. Both situations are classic examples ofthe short-to-ground or intercircuit shorts described inchapter 1. These shorts not only cause skips, sputters,and misfiring, but they are unsafe.

Remember! We want ignition protection at alltimes on gasoline-powered boats, and any straysparks from the high-tension side of your ignitionsystem clearly preclude that. Keep all of your ignitionparts clean and free from any oily buildup at alltimes. If necessary, use one of the many productsreadily available for engine degreasing.

Ignition-System TroubleshootingProblems with your boat’s ignition system can bebroken down into six general categories, listed below.You should attack the ignition system only afteryou’re certain that the fuel system and your engine’scompression are up to snuff; the procedures for do-ing those things are not covered in this book but arementioned in your service manual. If you don’t havesome experience in mechanics, you should get pro-fessional help rather than troubleshoot on your own.You’ll need to carefully follow the procedures foundin your engine’s workshop manual for some of theitems listed here.

� Engine runs sluggishly and overheats. Check the

ignition timing and spark-advance system.

� Engine pings. Check the ignition timing and

spark advance. Make sure the spark plugs are of the

recommended type.�

Engine is hard to start. Check for spark at the

plugs and the spark plugs themselves. Check the ig-

nition-bypass circuit, the battery and associated

wiring, and the distributor cap. Figures 7-12 and

Fig. 7-4. Photo of Deutsch-type gang plug. These offer thebest waterproof connections and are now widely used by en-gine makers.

107


7-13 on page 113 show my favorite spark tester in

use, but more on that later.

� Engine misfires. Check the spark plugs and leads,

rotor and distributor cap, and ignition coil for

loose connections at the coil and ignition switch.

Also check the engine firing order, plug wire rout-

ing, and the engine timing.

� Engine fires when cranked but stops when keyis released. Check the ignition switch and related

wiring.

� Engine cranks but doesn’t start. Check for spark

at the plugs; check the coil and bypass circuit to

the coil positive terminal; and check the wiring.

Also check the engine timing and plug wire rout-

ing, and the tachometer and related wiring.

Some of the items mentioned here, such as enginetiming and tachometer wiring, have not yet been dis-cussed, but I will cover them in the following sec-tions. This list is a guide for inboard and inboard/outboard (IO) engines only. Use it for sorting outyour thoughts as you approach a problem. You mustwork with the specific information for your ignitionsystem if you expect to be successful as an ignition-system diagnostician.

I will discuss two of the most common inboardengine electronic ignition systems, the MerCruiserThunderbolt IV and Thunderbolt V. Other widelyused systems with similar design and features aremade by Prestolite and Delco. Use this chapter as aprimer on electronic systems in general, and refer tothe workshop manuals for the specific informationyou need to troubleshoot these other systems.

MerCruiser Thunderbolt IV and Thunderbolt V SystemsWith about 75 to 80 percent of the market at this writ-ing, MerCruiser is the largest producer of gasoline-fueled inboard engines in the world. The Thunder-bolt series of ignition systems has been quite popu-lar over the years, and for the last 15 years the SeriesIV and Series V systems have been the mainstay ofthe MerCruiser line. The Thunderbolt IV system

comes in two variations, one with a remotelymounted ignition module (located on the port sideexhaust elbow) and the other with the ignition mod-ule mounted on the side of the distributor body.

Repair procedures for both variations are thesame. Ignition-module replacement will be slightlydifferent.

Service procedures for this system are not too dif-ficult. Besides the generic procedures already men-tioned for ignition systems, some specific systeminformation follows.

Distributor-Cap ServiceThe distributor cap needs to be kept clean and dry.MerCruiser recommends periodically removing thecap (annually will be fine) and giving it a thoroughinspection. Be sure to mark the high-tension wireswith tape and a marker before removing them fromthe cap so you can be certain they go back in thesame order.

Loosen the four screws that hold the cap in placeand carefully lift the cap off its seat on the distributor.There should be a gasket between the cap and theedge of the distributor housing; be careful not todamage it. If it’s damaged in any way, it will have tobe replaced. This gasket is an integral part of the ig-nition protection for the distributor. Look closelyand observe the alignment tab molded into the capand the corresponding indent on the body of the dis-tributor housing. Upon reassembly, make sure thistab and groove are aligned; otherwise, damage to thedistributor cap and rotor can occur the first time theengine turns over, regardless of whether it starts ornot. Figure 7-5 on page 108 shows the cap orienta-tion with the position of the tab indicated.

Once you have the cap off, clean it thoroughlywith warm soap and water and dry it (use com-pressed air if you have a supply). Next, carefully in-spect the cap looking for excessive burning orcorrosion. Check the center contact for deteriora-tion. Minor corrosion, which is not unusual, can beremoved with the tip of a straight-bladed screw-driver. Look for any signs of carbon tracking on boththe inside and outside of the distributor cap. Carbontracks will show up as random, fine lines etched into

108


the surface of the plastic. These tracks, often mis-taken for cracks, are actually secondary voltage leaksshort-circuiting the intended path. The spark actuallyetches a carbon groove into the surface of the cap.Carbon tracks are most often caused by dirt and oilaccumulation on the cap. If there are any signs of car-bon tracking, the cap will have to be replaced. Fig-ure 7-6 shows a carbon track on the inside of afour-cylinder distributor cap.

Next inspect the rotor-sensor wheel, located un-der the distributor cap. Again, you’ll be looking forcorrosion and any signs of carbon tracking.

One problem with the Thunderbolt system is thatthis rotor is attached to the distributor’s center shaftwith a product known as Loctite. As the name im-plies, Loctite is a kind of glue that secures the rotor tothe shaft. Unlike most rotors that simply lift off theshaft against the pressure of a small spring clip, theserotors are on tight. Don’t expect to simply lift it offfor inspection.

To remove the rotor, place two flat-bladed screw-drivers under the rotor at its base and push them

snugly up against the distributor shaft. The screw-drivers should be at 180 degrees from one another.Push both screwdrivers down against the distributorhousing, and hope the rotor pops off. If this doesn’twork, use an electric hair dryer on high heat and fanthe rotor and sensor wheel until they begin to feelwarm to the touch. Try prying again, but don’t bendthe sensor wheel blades. The slightest distortion ofthe wheel will render it useless, so alignment of theblades with the sensor inside the distributor is criti-cal. With diligence, the rotor will eventually lift off.

Once the rotor is removed, carefully inspect it forcarbon tracks and any damage to the key inside thecenter section. Replace the rotor if there is any dam-age here. If all looks well, ensure that the tang that’sattached to the rotor and follows the center contactinside the distributor cap is bent to allow for 1⁄4 inch (6mm) clearance, as shown in figure 7-7.

Ignition SensorNext, take a close look at the ignition sensor. It’s bestto use a magnifying glass for this, because you’ll be

Fig. 7-5. Distributor cap showing positioning tab. Make surethis tab is lined up with its corresponding groove in the distributor housing when reinstalling the cap.

Fig. 7-6. Carbon tracking inside a distributor cap. Thesetracks provide a highly conductive path for your ignitionvoltage to short-circuit between cylinders.

109


looking for hairline cracks, called jumpers, in themetal connecting links on the sensor. If you find anycracks, replace the sensor. Figure 7-8 shows the sen-sor and points out the jumpers in question.

If the sensor does require replacement, it’s easilyremoved at this point by backing out the two retain-ing screws indicated in figure 7-9.

When you reassemble the distributor, you’ll needsome Loctite (#271), which is available at any goodauto-parts store. Apply several drops to the inside ofthe rotor at the positioning key and put several dropsin the keyway on the distributor shaft where the keyfits into the rotor. Immediately reinstall the rotor. Do

not, under any circumstances, use a silicone-basedsealer on the inside of the distributor (to repair thecap gasket, for example). As they cure, most siliconesealers give off acidic vapor that can cause corrosionon the ignition contact points and conductors insidethe distributor.

MerCruiser Thunderbolt V SystemThe Thunderbolt V system offers some significanttechnological advantages over the Thunderbolt IVsystem, the most significant of which is known as theknock-retard spark control. This feature is a giant stepforward in avoiding internal engine damage due topinging. Engine cylinders are designed so that thecompressed gas-air mixture burns very rapidly butprogressively. When the mixture explodes instead ofburns, a loud rapping or “pinging” noise is heard.Thus, pinging is sometimes called detonation.

Whatever it’s called, pinging is bad for your en-gine. Incorrect timing, low-quality fuel, or excessivecarbon buildup inside the combustion chamber arethe primary causes. If it’s allowed to continue, ping-ing will eventually cause valves and piston tops toliterally melt away.

By adding two electronic devices to the ignitionsystem, engineers have devised a way to minimize

Fig. 7-7. Rotor contact bent to allow 1⁄4 inch clearance.

Fig. 7-8. MerCruiser ignition sensor, pointing out metaljumpers. These jumpers are famous for corroding through,effectively shutting down your ignition system.

Fig. 7-9. Retaining screws holding an ignition sensor inplace.

1⁄4 "

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pinging as a cause of engine damage. The knock-retard spark control is operated by one of these twoadditional devices.

The knock-control module receives an electricalsignal from a sensor, called a knock sensor, which isscrewed into the engine block. This sensor “hears”any pinging inside the combustion chambers andsends an electrical pulse to the knock-control mod-ule. The module then sends a signal to the ignitionmodule, ordering it to retard the ignition timing insmall (3-degree) increments until the pinging stops.

In addition to controlling ignition timing to elim-inate pinging, the Thunderbolt V also controls engineover-revving, acceleration, spark advance, and idlespeed. It also has a feature called mean best timing,although this feature is not available on all engines.

Mean Best TimingMerCruiser’s Thunderbolt V system uses a sophisti-cated feature called mean best timing (MBT) thatfine-tunes the ignition timing during light-loadcruising. The ignition-control module searches forthe perfect setting for ignition timing by automati-cally adding a few degrees of advance and waiting tosee if the engine rpm increases. If so, the module willadd a little more advance until engine speed stopsincreasing. If the rpm drops for any reason, such asa change in sea conditions, the module will automat-ically retard ignition timing as needed. This is trueelectronic wizardry at its finest.

Idle-Speed Spark ControlThe idle-speed spark control automatically adjustsignition timing so that a specific idle speed is main-tained under different operating conditions. This isaccomplished by making small spark-advance ad-justments and is only used within a speed rangethat generally falls between 400 and 700 rpm. Thisvariation in exact speed specifications is one of sev-eral reasons that if module replacement is everneeded, the exact module for your engine (as de-termined by the serial number of the engine) mustbe used.

Don’t be fooled into thinking that a module thatlooks just like yours is the correct one for your en-gine; the internal calibration of the look-alike couldbe very different from yours.

Acceleration Spark AdvanceAll ignition systems need some sort of acceleration sparkadvance mechanism. Older systems with breaker pointsused a mechanical advance with centrifugal weights at-tached to the plate inside the distributor to which thepoints were attached. As engine rpm increased, it gener-ated centrifugal force and the weights moved the ignitionpoints relative to the center shaft within the distributor.This changed the place where the points opened andclosed, and adjusted the timing of the spark. On newerengines with electronic ignition, timing is controlled bythe ignition-control module or, on the latest computer-ized engines, by the onboard microprocessor.

This change in timing allows more time for thefuel-air mixture to completely burn as engine speedincreases. The faster the engine turns, the more timeis required for combustion, and the more the timingmust be advanced. When the engine is accelerating,the ignition-control module may add more spark ad-vance to the “base timing” (the starting point fortiming on all engines). The amount of spark advanceadded depends on how fast engine rpm increases.Rapid throttle changes induce rapid timing changes.

Beyond the Basics: Outboard and PWC Ignition SystemsOn outboard and personal watercraft (PWC) ignitionsystems, some of the parts are located under the en-gine flywheel. So if your diagnosis leads you here, youmay need the services of a professional mechanic whohas the tools needed to get at these parts. All manu-facturers include test procedures in their workshopmanuals that use special test equipment, such asStevens or Merc-o-tronic ignition system testers. Thisequipment is too expensive to be a part of your toolkit. Unless you do this sort of work daily, it just isn’tpractical to have this stuff. This section will show youhow to narrow down the most common ignitionproblems using simple tools and your multimeter.

Capacitive-Discharge Ignition SystemIf your engine was built after 1975, it most likely hassome variation of a capacitive-discharge ignition

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(CDI) system, which works by charging a capacitor andreleasing this charge to the appropriate igni-tion coil atjust the right time. We have already taken a brief look atthis in the overview of how out-board and PWC ignitionsystems work earlier in this chapter.

Different engine makers use different names todescribe the parts they use in their CDI systems, butthey all are similar.

Magnets carefully positioned on the engine’s fly-wheel induce an electric current as they rotate pastspecially designed coils located very close to the mag-nets. One of the coils under the flywheel is called acharge coil. As the flywheel magnets spin by, this coilsends a fairly high alternating current voltage to theignition-control module, which is sometimes calledthe power pack, or CDI unit. This will be around 200volts AC, depending upon which system you have.

As already mentioned, the other ignition coilsfound under the flywheel are called sensor (OMC),pulsar (Yamaha), or trigger coils (Mercury). I will callthem trigger coils here to avoid confusion. The trig-ger coils send electrical signals to the CDI unit to tellit which cylinder to work with at the correct time.

Next you’ll find the CDI unit itself. This device isthe brain of the system and serves several functions.First, it converts the alternating current from thecharge coil into usable direct current. Next it storesthis current in the built-in capacitor mentioned ear-lier. The CDI unit also adjusts timing by changing theinterval at which the trigger coil sends a signal to themodule. The timing changes with any change in en-gine rpm and is adjusted by a change in the relativeposition of the trigger coil to the flywheel magnets.

A timing plate to which both the charge and trig-ger coils are mounted controls this adjustment. Me-chanical linkage connected directly to the enginethrottle linkage constantly adjusts the timing relativeto the position of the carburetor throttle. In addition,the CDI unit electronically controls the discharge ofthe built-in capacitor and sends this voltage to the ap-propriate primary side of the ignition coil for the cor-rect cylinder.

The CDI unit may also have electronic circuitswithin it to limit engine speed to prevent over-revving, and some even have a circuit that reduces

engine rpm if for any reason the engine begins to runtoo hot. Some of the larger engines may automati-cally advance ignition timing during initial start-upand when the engine is running at temperatures ofless than approximately 100 degrees.

Manufacturers often use one CDI unit for eachbank on V-type power heads. One module will con-trol the odd-numbered cylinders and the other willservice the even-numbered cylinders. Once the volt-age leaves the CDI unit, it’s sent to the high-tensioncoil, which is similar in design to the inboard-systemtype already discussed. Here, the voltage is steppedup to anywhere between 15,000 and 40,000 volts, thevoltage that’s required to jump the air gap in thespark plugs. The high-tension ignition coil has twosides, primary and secondary, just as it does on aninboard system. It’s really two coils combined intoone neat, compact case. Figure 7-10 shows the in-ternal construction of a typical ignition coil with pri-mary and secondary windings.

The coil works by using magnetic induction, justlike one on an inboard engine. The voltage gener-ated by the primary winding creates a magnetic fieldaround the secondary winding, which has manymore windings than the primary coil. The CDI unitcontrols the rapid turning on and off of electricalflow in the primary winding, thereby turning thismagnetic field on and off. The effect of this is thesame as described earlier. The rapid movement ofthis magnetic field past the secondary windings in-

PRIMARY12 Turns12V 20A

SECONDARY120 Turns

To circuit

Fig. 7-10. Typical internal construction of an ignition coil,showing the primary side windings (with fewer coils) andthe secondary side (with more windings).

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duces electrical current. The more windings, themore current is produced.

As the secondary voltage leaves the center towerof the ignition coil, it travels through the spark-plugwire (the high-tension lead), which is heavily insu-lated and designed to carry high voltage. If all is well,the high voltage will jump the gap between the centerelectrode of the spark plug and the ground electrode,completing a circuit to ground. On larger engineswith surface-gap plugs, the side of the spark plug isthe ground electrode. Figure 7-11a shows both plugtypes. Figure 7-11b shows a spark-gapping tool beingused to adjust the electrode gap.

Engine Stop ControlLast, but certainly not least, is the stop control—thedevice you use to shut off your engine by disablingyour ignition system. Depending on the engine, thestop control might be activated by a simple stop but-ton or, on larger engines, by a key switch. On newerengines, you’ll find an emergency-stop button withan overboard clip and lanyard wired directly to yoursystem’s CDI unit. When the lanyard is pulled, theclip is yanked out of the stop button. This creates amomentary short circuit inside the CDI unit that di-verts the voltage intended for the high-tension coilsdirectly to ground and shuts off the ignition longenough to stop the engine. These stop circuits cancause a lot of problems, and procedures for testing

them will follow a little later in this chapter.

Outboard and PWC Ignition TestsThe first step with all electrical-circuit testing is tocarefully use your eyes. Look for the obvious! When-ever a problem develops with any engine or systemthat has been regularly maintained, troubles are al-most always due to some minor oversight and areeasily solved. Check all the wiring for any loose con-nections on your engine. Look for signs of corrosionon terminals and connectors. Check for any brokenor frayed wires. Make certain the problem is notsomething as silly as a blown fuse. Any of these thingscan be the cause of ignition problems, and they canbe quickly fixed with basic tools.

Testing for SparkAs with the inboard systems, the first step in trou-bleshooting your ignition system is to verify thatyou’re getting spark. However, with outboard andPWC systems you need to check each cylinder becauseeach cylinder has its own high-tension coil, and partialsystem failures of one cylinder are not uncommon.When checking the coils, it’s extremely important thatyou check for any fuel leaks and make certain that allfuel line fittings and connections are secure.

It is a good idea to create some shade near the

Fig. 7-11b. A spark-plug gapping tool.Fig. 7-11a. Surface gap and traditional spark plugs.

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spark-plug wire you’re checking. It’s very difficult tosee a spark jump a gap in bright sunlight. Use thespark tester shown in figure 7-12. Adjust the knurledknob on the tester to give an air gap of about 3⁄8 to 7⁄16

inch between the two pointed contacts inside thecylinder. Figure 7-13 shows the spark tester properlyconnected and ready to go. Hold the tester so you cansee inside the cylinder as shown, and crank the en-gine. You should see a bright blue spark (not yellow)jumping between the two contacts. If you do, then ig-nition output is satisfactory. If not, further investi-gation will be needed.

If your engine is skipping or misfiring, check all ofthe spark-plug wires this way to be sure that each sec-ondary coil is sending a spark through its respectiveplug wire to the spark plug. The beauty of this sparktester over similar tools is that the air gap between thetwo contacts is adjustable. This is important becausesome manufacturers will give an air gap specifica-tion in their manuals. The wider the air gap a sparkwill jump, the higher the total ignition-system out-put. So, by comparing the maximum gap that a sparkwill jump for each ignition coil, you can find a weakor faulty coil.

Be careful not to get the spark plug wires mixedup when you do this test. Each wire is timed to a spe-cific cylinder and must be replaced on the same sparkplug from which you removed it. If you don’t see aspark, check the fuse for the ignition system and re-place it if it is blown. Also, if you have one, make sure

the emergency-stop button and clip are set correctly.It’s amazing how easy it is to forget this simple de-vice. Check for spark again; if it’s still not evident,further investigation will be needed.

Checking the Spark PlugsJust because you’re getting adequate spark to thespark plugs doesn’t mean the spark plugs are firing.They could simply be worn out, but there are manyother things that can cause a spark plug not to fire.An oil blend that’s too rich (too much oil in the gas),a weak spark to a given cylinder, incorrect heat-rangespark plugs, and fuel system problems are just a few.If you have regularly serviced your engine, worn-outplugs should not be a consideration.

So, what’s left? Look at the plugs and verify thatthey can actually fire. Remove the plug using a ratchetand spark-plug socket, or use the plug wrench suppliedin the tool kit for your engine, and look it over. Theplug should not be soaked with black fuel-oil mixture.Are the center and ground electrodes intact? If not,throw away the plugs and put in a new set.

Attach toground

Spark PlugWire attaches here

Spark arcs here

Adjustable Knob

S E03

0 2 04 0

Fig. 7-13. Spark tester in use.

Fig. 7-12. Snap-On spark tester. I prefer this type over allothers because it’s adjustable, which gives you the ability todetermine the strength of the available spark.

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If the plug’s center and ground electrode are OKand the plug is gapped correctly, check the numberon the plug and match it to the manufacturer’s rec-ommendations. It may be the wrong heat range forthe engine. If all of these things check out OK, insertthe plug into the correct plug-wire boot, wedge theplug into a spot on the side of your engine, as shownin figure 7-14, being sure that the metal case of theplug is grounded, and crank the engine. If you see ablue spark jumping from the center electrode to theedge of the plug on a surface-gap plug or to theground electrode on a standard plug, the spark plugis OK and should fire in the cylinder.

If you don’t see a spark, or if you see a weak yel-low one and you’re sure that adequate current wasgetting to the plug, the plug must be replaced. If it’sa standard plug, check the gap before installing thenew plug as shown in figure 7-11b on page 112. Sur-face-gap plugs require no adjustment.

Spark plugs are among your most valuable diag-nostic tools. Whenever you remove your plugs, keepthem in order for the cylinders they came from.Check each plug; carefully look for cracks in the ce-ramic insulator body, black oily buildup, or discol-

oration on the electrodes. A spark plug that’s burningcorrectly will show a light brown “fluffy” colorationon the center electrode and a fluffy black colorationon the metal base. The ground electrode will be alight gray-brown color.

One last thing regarding spark plugs: be carefulnot to over-torque when reinstalling them into thecylinders. It’s a good idea to put a light coating ofwhite grease on the threads before screwing the plugsback into the cylinder head. Screw them in by handuntil the sealing washer seats; then use your spark-plug wrench or a socket and ratchet to tighten theman additional half to three-quarter turn. Any moretorque than that could damage the plug threads inthe cylinder head. You should never replace just oneplug. Replace them in sets and don’t bother savingthe old ones for use as spares. (They actually makegood sinkers for offshore fishing.) You should alwayshave a fresh set of gapped and ready-to-go plugs onboard your boat—just in case.

Ignition Problem Quick-Check ListIf you have checked the spark plugs, as describedabove, and determined that you don’t have a sparkat any of the cylinders, or you have a spark at somecylinders and not at others, further investigation isneeded. The following list will help organize yoursearch through the ignition system, and the accom-panying tests will help you to pinpoint the source ofa problem. These tests should only be completed us-ing this book and the manual for your particular en-gine. Each manufacturer uses different color codingfor wires and slightly different test procedures fortheir respective systems. However, by following thisguide you should be able to trace your way throughyour system and isolate any problems in the CDI unitin the rare instances when you have a problem.

These tests assume that you have eliminated anypossibility of a problem with fuel or compression.The sequence for testing your outboard or PWC ig-nition system is as follows.

1. Check to see if your engine has a fuse for theignition system. If it does, check the fuse andreplace it if it’s blown or corroded.

Fig. 7-14. Testing a spark plug to see if it fires.

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2. Check the spark-plug wires.

3. Test all the ignition coils.

4. Do a water-spray test of the engine.

5. Test the charge and trigger coils and output tothe CDI unit using your multimeter and Mer-cury DVA tester (part number 91-89045).

6. Test all engine stop circuits.

7. Test the tilt switch, if your engine is equippedwith one.

Let’s discuss the details for each of these proce-dures in a little more detail.

Testing Spark-Plug WiresTesting spark-plug wires is easy. If you have alreadyused the spark tester and seen a spark at the end ofthe spark-plug wire, you know the wire is conducting

electricity to the plug. But that’s not all the wire hasto do. It also has to insulate this electricity under allengine-operating conditions and conduct electricitywhen your boat is underway and the engine is vibrat-ing. Look at the wire and the wire ends inside theprotective boots. Look for any sign of cracking, worninsulation, and any sign of green corrosion on themetal clips that lock the ends of the wire to the coiland spark plug. If you find corrosion, slide the bootback onto the wire and carefully clean the connectorwith a wire brush until the metal is bright and shiny.If the wire is chafed or cracked, replace it.

To check the wire electrically, set your multimeteron the low-ohms scale and insert the meter probesinto the wire as shown in figure 7-15. The metershould read near zero ohms, except on some of thenewest engines, where “resistor-type” wiring is used,in which case some resistance will be indicated onyour meter. Next, hold the probes in place and bendand flex the wire while carefully observing the me-ter. If the reading fluctuates, there is a break in thewire inside the insulation. Replace the wire.

When reinstalling ignition wires, make sure touse the hold-downs found on many engines. Thesehold-downs keep the wire from coming in contactwith moving engine parts that may chafe the wireand ultimately cause it to fail. Apply a light coatingof waterproof grease to the ribbed ceramic insulatorand metal connector of the spark plug and coil con-nector before reinstalling the spark-plug wire. Thegrease will help the boot to seal out moisture thatwould eventually corrode the metal connector onthe end of the wire.

Testing High-Tension CoilsIn the repair shop, a technician normally uses oneof the testers specially designed to work with CDIsystems. These testers are quite expensive andshould not be a part of your tool collection, eventhough not having one will limit your ability to doadvanced ignition-system tests. You can, however,do many tests with your spark tester, your multi-meter, and a spray bottle filled with fresh water.These simple tests will enable you to narrow downpossible causes of an ignition fault and in most cases

Fig. 7-15. An ohmmeter test of a spark-plug wire. Dependingon your engine type, you may or may not measure resistanceof any value when performing this test. With “resistor-type”wires used on some of the newest engines, readings of5,000–10,000 ohms for each foot of wire length are not un-common.

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find the culprit behind it. At the very least, you’ll beable to point the professional mechanic in the rightdirection and save on expensive labor charges.

As already stated, each of your ignition coils is re-ally two coils combined into one unit consisting of aprimary winding and a secondary winding. The trickis to identify which external coil wires and connec-tions go to which coil inside the insulated case. To dothis you need the wiring diagram and workshop man-ual for your engine. Using the diagram in the manualas a guide, check the resistance of each of the coilwindings with your multimeter’s ohmmeter. If youfind electrical continuity and normal resistance, youcan be reasonably certain your coil is OK. If you findexcessive resistance, or if the meter indicates an opencircuit within the coil, then the coil must be replaced.

Figure 7-16 shows these tests on a typical out-board engine high-tension coil. Remember, though,

that you must identify the correct wire connectionsand resistance values for these tests to work on yourspecific make and model of engine.

Whenever removing an ignition coil from yourengine, carefully note the location of any insulatingwashers that you find under the coil or the hold-down bolts. Misplacement of these washers can causea no-spark condition with a perfectly good coil.

Water-Spray TestAnother simple test for determining the integrity ofyour secondary ignition system is to run the engineand use a spray bottle with fresh water to wet the areaof the ignition coils, spark-plug wires, and sparkplugs. Do this in the shade or at dusk. Any weaknessin the insulation of connecting boots, high-tensioncoil cases, or spark-plug wires will immediately showup as sparks jumping from the poorly insulated wireor connection. Any component that shows sparkshould be replaced.

Testing the Charge CoilsFor these tests you’ll once more need to consult yourengine’s workshop manual. Remember, your chargeand trigger coils are located under the engine fly-wheel and you can’t see them without removing it.Removing the flywheel goes beyond routine testing,and is not within the scope of this book. You can,however, still test the charge and trigger coils for con-tinuity and for a possible short to ground. You canalso test for voltage using the Mercury DVA testerand your multimeter.

The charge and trigger coils are just like your high-tension coil. They are made with a long, tightly coiledwire insulated from ground. Charge coils have higherresistance than trigger coils, so they can generatehigher voltage than do trigger coils. This means thelength of wire in a charge coil is much longer than thatin a trigger coil and therefore has a higher resistance.

The wiring harness for these coils is always se-cured to the movable timing plate under your en-gine’s flywheel and usually exits from under thisassembly on the starboard (right side looking towardthe bow of the boat) of the engine power head.

Once you have located the harness and found allthe wires that come through it, match the color cod-ing on the wires to your wiring diagram and deter-

Fig. 7-16. Using the ohmmeter to test the resistance throughan outboard-engine ignition coil: testing for a short circuitto ground (top) and testing resistance through the coilwindings (bottom). Make sure to get the proper specifica-tions for your engine from the workshop manual.

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mine which wires go to and return fromthe charge and trigger coils. These wiresoften terminate in a gang plug that con-nects to the CDI unit. Disconnect thisplug to continue testing.

To test the charge coil, set your ohm-meter to the scale for the expected resis-tance as specified in your enginemanual. Insert the red and black testprobes into the plug socket that matchesthe correct color wire and take a read-ing. Charge coils generally have resis-tance between 400 and 900 ohms. If thereading is more than that or if a readingof infinity indicates a break in thewiring, the charge coil is defective andmust be replaced.

Next, check for a short to ground byremoving one of the meter probes fromthe plug assembly. Now switch your me-ter to the high-ohms scale (if it’s notself-scaling) and touch the free probe tothe metal timing plate to which the lead harness is se-cured. Any reading on the meter other than “OL”indicates a short to ground. The flywheel must be re-moved to correct the problem, which is either frayedor melted insulation or a bad charge coil.

To test the continuity of the trigger coil follow theabove procedure for the charge-coil tests, only adjustyour meter to a much lower resistance—between 15and 50 ohms is usually about right. To test for a shortto ground in the coil lead, set the meter on the samehigh scale as for the charge-coil short test. If your en-gine is equipped with more than one trigger coil, testthem all.

Figure 7-17 shows these tests and the point atwhich the wiring harness emerges from under the fly-wheel. It also shows the timing-plate assembly.

To test for voltage from these coils you need theDVA adapter shown in figure 7-18 and availablethrough outboard engine dealers. This adapter can beused with any system of this type and converts theAC voltage from your charge and trigger coils to aDC voltage your multimeter can easily read. Suffi-cient readings from 1 to 9 volts will not only attestto the performance of the coils but also verify that the

magnets under the flywheel have enough magnetism.As you know, voltage increases in direct proportionto the speed of the engine and the strength of thesemagnets.

To test voltage, plug the red lead from the testerinto the DC volt socket on your multimeter and

Fig. 7-17. Continuity tests through the trigger-coil test and the short-to-ground test. Again, you’ll need your workshop manual to get the properspecifications for these tests.

Fig. 7-18. DVA adapter.

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connect the black lead from the tester to the groundor negative socket. Next, plug the red and blackprobes from your meter into the correspondingsockets on the DVA tester, and you’re ready to take avoltage reading.

To test the charge coil, set your voltmeter to ascale that will read about 400 volts. Typical read-ings at cranking speed for charge coils are between150 and 275 volts. You must check the workshopmanual for your engine to get the exact specifica-tions. Plug the meter leads into the socket or con-nect them to the leads coming from the chargecoil. Again, your manual will help you identifythese two wires.

Crank the engine or use the pull cord to turn itover while you take a reading from your meter. Youmay need a second set of hands here. Some of thenewest meters have a “peak-reading” button thatwill hold the reading until you can look at the me-ter. If your reading is within specifications, thecharge coil has tested OK and is not causing anyignition problems.

Testing the Trigger CoilsNext, test the trigger coil the same way you tested thecharge coil, only switch your multimeter to a voltagescale of 20 volts or less. Typical trigger-coil voltagereadings will be between 1.2 and 9 volts at crankingspeed. Again, verify the specification in your enginemanual. Make sure to check all the trigger coils if yourengine is equipped with more than one.

Testing the CDI UnitNext, using the multimeter and DVA adapter, testthe CDI unit for voltage to each of the high-tensioncoils. Be sure the ground wire for your CDI unit is se-cure, as damage to the module could occur if it’s not.Use this ground to attach the black probe from yourmultimeter-DVA combination. It’s a good idea touse a wiring diagram to locate the stop circuit groundlead for your ignition module and disconnect it fromthe stop circuit; this isolates the CDI unit from thatcircuit and eliminates the possibility that a defect inthe stop circuit could cause you to misdiagnose yourCDI unit as faulty.

Next, switch your meter to a scale that will readabout 400 volts (or allow it to self-scale). Locate the

high-tension coil primary-feed wire, which is thewire that runs from the ignition module to the coil.Attach the multimeter’s red probe to the terminalon the high-tension coil, and crank the engine.

Your reading here, which should be somewherebetween 150 and 350 volts, is the discharge from thecapacitor inside the ignition module. Match yourreading to factory specifications for your engine. Dothis test on each lead coming from the CDI unit.Your readings should be approximately the same foreach one. If you discover a lead with no output or a considerably lower output (check it against the specsin the workshop manual), the ignition module is de-fective and must be replaced.

Some of the latest CDI systems use a module withan integral trigger coil, and the module is located un-der the flywheel. In this case, you won’t be able toget at the charge coil to service it, and you won’t findany reference to trigger-coil testing in your workshopmanual. The flywheel must be removed to servicethese parts; you’ll need the services of a dealer or an-other pro if your tests on the plugs, secondary wiring,and high-tension coil lead you this far.

Problems with charge coils, trigger coils, and thepermanent magnets under the flywheel are extremelyrare and something that you may never have to dealwith on your engine. The only thing that usuallycauses early failure of these parts is accidentally sub-merging the engine in salt water and not properlycleaning it. A saltwater dunking will cause excessivecorrosion in all the parts under the flywheel and, inmost cases, ruin the engine if it isn’t tended to rightaway. If you should dunk your engine in salt water,flush it with fresh water and get it to your dealerwithout delay.

So, you have checked for spark to your sparkplugs. You now know how to check your system’sspark with a simple spark tester. You can removeyour plugs, check them, and replace them when it’snecessary. You can check your spark-plug wires andhigh-tension coils, and with the help of your work-shop manual you can check your charge and triggercoils. Permanent magnets rarely lose their magnetismand don’t need to be checked. So what’s next? Yourengine stop circuits and a few thoughts on some ofthe other functions your CDI unit may have.

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Testing Your Stop SwitchYour engine, depending its size and the way it’s in-stalled, might have a remote key switch to turn theignition on and off, or it might have a simple stopbutton mounted on the engine or steering tiller. In ei-ther case, the tool of choice for testing the stop-switchcircuit is your multimeter, set to read resistance. Youalso need the wiring diagram for your engine.

If you don’t have a remote-control starter switch,look under the engine cowl where the wiring and ca-ble controls come out of the steering tiller. Youshould find two wires, one going to ground and theother going to the CDI unit. Verify you have the cor-rect wires by checking your engine-wiring diagram.Next, find a good ground on your engine. Install theemergency-stop clip if your engine has one, andmake sure your engine is ready to run.

Connect your multimeter’s black probe toground and the red probe to the plug or to the wirecoming from the stop button. If all is well, you’ll geta high (infinity) reading, indicating an open circuit.Any reading showing continuity indicates a defec-tive switch or a short to ground in the wire comingfrom the switch somewhere inside the tiller handle.In either case you’ll have to replace the assembly.

If all appears to be OK to this point, push in thestop button and check your meter. It should indi-cate continuity with a low reading. Finally, if youhave a stop clip, pull it out and observe your meterreading. It should again show a low reading. If push-ing the stop button or pulling the emergency clipdoes not give the desired low ohmmeter reading, theassembly must be replaced.

Figure 7-19 shows a typical meter hooked up forthese tests.

On larger engines with a remote-starter switch,you still check the switch for short circuits to ground;you’ll just have to cover the distance between yourengine power head and the key switch. Use yourohmmeter and your engine’s wiring diagram just asbefore. Identify all the terminals and connections onyour key switch by removing the back cover of thecontrol unit to get at the back of the switch. Somemanuals show a detailed picture of the plug assemblycoming from the back of the switch and identify all

the terminals and connections. If you can get at theplug in this case, you won’t have to remove the re-mote-control assembly.

If removal and partial disassembly of the remote-control assembly are necessary, carefully follow theinstructions for opening the control unit. In somecases removal of the central pivoting screw can cre-ate quite a mess, and it can be difficult to reassemble.If the remote-control assembly has a key switch sep-arate from the shift control, this central-pivot screwwill not be a problem. You can usually access theback of the switch without removing the switch fromthe panel.

Now use your wiring diagram to identify the wirecoming from the back of the ignition switch to theground shut-off at the power pack. As with thesmaller engines, this wire will usually terminate at agang plug under the engine cowl in the harness goingto the power pack. Once you find it, disconnect theplug or connection to the remote-control assembly.Now you’re ready for your ohmmeter tests. Checkat the engine end first, and, for your multimeter’ssafety, be sure your battery is disconnected beforedoing this test.

First, connect the red probe on your ohmmeter tothe wire that runs from the ignition switch to the re-mote-control assembly. Connect the black probe to agood ground. With the ignition key on, you shouldget a high reading or infinity. If your meter indicatesa complete circuit with a resistance reading near zero,

Fig. 7-19. Multimeter tests of an outboard-engine stop circuit.

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disconnect this wire from the backof the ignition switch and recheckthe meter reading. If the meter nowreads infinity, the ignition switchis faulty and must be replaced.

If the meter reading has littleor no resistance, it indicates acomplete circuit to ground, mean-ing the wire that connects the igni-tion switch to the engine isshorted to ground and must be re-paired. If all of these readingscheck out, turn off the key switchand check your meter. You shouldhave a low resistance reading nearzero ohms. If your meter still givesa reading of infinity, check that theground for the key switch is con-nected and in good condition. Ifit is, you may have a break (opencircuit) in the wire leading fromthe switch to the terminal on theengine. Check the entire length ofthis wire for a break and either in-stall a new wire or splice the break.

Figure 7-20 shows a typicalwiring diagram for a remote-keyinstallation with the typical testpoints shown and the possibly faulty wires indicated.

If after testing the stop circuit you still have a prob-lem with your engine not shutting down with either thekey switch or the stop button, the fault is in the CDIunit itself. Unfortunately, it’s a solid-state sealed de-vice and is not repairable; it will have to be replaced.

Mercury Tilt-Stop Switch TestingSome mid-sized and larger outboards have a switchdesigned to cut out the ignition if the engine istrimmed up too much. It’s located in the trim-mounting bracket assembly. The tilt-stop switch prevents the lower-unit water-pickup port from rais-ing out of the water enough to cause inadequate water flow. Figure 7-21 shows this switch on a 70-horsepower Mercury outboard.

To test the tilt-stop switch, remove the mount-ing screw that secures it to the engine. Disconnect the

remaining lead coming from the switch. Now withyour multimeter set to the low-ohms (R × 1) scale,connect the meter probes to the two switch leads (itreally doesn’t matter which probe goes where) andposition the switch in your hand as it would normallyrest on the engine with the trim down. The switchshould be open, and the meter should read no con-tinuity or infinity.

Next, tilt the switch in your hand and tap the highend of the switch with your finger. The switch shouldclose, and the meter should now indicate continuitythrough the switch. If your test readings are not asdescribed here, replace the switch.

Final Checks and Ignition TimingIt is possible to thoroughly test all of the ignitionparts, have everything check out, and still not have

Remote control with key switchand neutral safety switch

Remote controlharness plug

Battery,Positive cable

Ignitionmodule

Electricaljunction

Solenoid

Engineground

Startermotor

Battery,groundcable

12 voltBattery

Fig. 7-20. Typical wiring diagram for an outboard-engine remote-key installation.

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any spark. Or you might have a strong spark and anengine that backfires when you try to start it or onethat misfires at high speed. Your ignition systemcould still be the culprit. Before blaming the CDI unitor ignition-control module for a no-spark conditionor bad timing (the backfiring), there are several addi-tional things to check.

First, be absolutely certain that all wires arehooked up correctly. It’s all too easy to cross plugwires, or switch primary-feed wires going to thehigh-tension coils so that the CDI unit sends its sig-nal to the wrong coil. Double-check everythingagainst your engine-wiring diagram. Gang-plugconnections are always keyed so they only go to-gether one way, but it’s easy to make a mistake onengines with individual terminals. To avoid the pos-sibility of crossfire between cylinders, make sure thatall high-tension leads go into the proper hold-downclamp on the engine.

Loose-Flywheel CheckNext, consider the flywheel. Remember that it hascarefully positioned magnets attached inside. The fly-wheel is keyed to the crankshaft so that these magnetspass the appropriate charge or trigger coil at a specificpoint in the engine’s rotation. On rare occasions,usually after the flywheel has been removed and im-properly reinstalled, the flywheel becomes loose onthe end of the crankshaft and shears off the key. Theflywheel may spin independent of the crankshaft andchange position of the magnets relative to the crank-shaft, ruining the ignition timing.

To check for a loose flywheel, disconnect the mas-ter plug to the ignition module to disable the ignitionsystem; you don’t want the engine starting with yourhands on the flywheel. Next, grasp the flywheel firmlywith both hands and feel for any side-to-side or up-and-down movement, as shown in figure 7-22. Anymovement indicates a loose flywheel. An experiencedmechanic must remove the flywheel, and the crank-shaft and flywheel must be inspected and repairedor replaced as needed. With luck, you’ll just need toinstall a new key and to re-torque the flywheel.

Fig. 7-21. Mercury tilt switch. This switch is designed to pre-vent engine starting with the prop out of the water. If it mal-functions (open-circuits), your engine won’t start with theprop in the water, either! In this picture I’ve removed theswitch and am testing its function with a multimeter set tocheck continuity when the switch is tilted manually. I’m ver-ifying with the meter that the switch turns off and on.

Fig. 7-22. Checking for a loose flywheel.

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Timing CheckIf all wiring is properly connected and your flywheelis secure, a timing check is in order. This is not a pro-cedure for the inexperienced outboard-engine me-chanic. The procedure varies somewhat for everyoutboard made, and verifying the position of the ignition-timing pointer is a precise and difficult jobrequiring special tools that the average boatownerwon’t have. The timing should be checked at idle andfor maximum advance at high speed. This is bestdone in a special test tank or with the aid of a dy-namometer specially designed for outboard engines.The average boatowner doesn’t have these tools.

If you’re well equipped and have a reasonableamount of engine experience, you can set the timingby following the procedure outlined in the EngineSynchronization and Timing section of your work-shop manual. On smaller, single-carburetor engines,the procedure is not especially complicated, and byfollowing the instructions carefully someone withlimited experience can do it. On the larger enginesof over 25 horsepower, do-it-yourself is not recom-mended. The variables here are many and go beyondthe scope of this book.

To sum up timing and its importance in ignition-system diagnosis, remember these important facts:Timing will rarely change unless someone alters the carburetor linkage or adjustments. Or the flywheel comes loose from the crankshaft. Or the fly-wheel magnets become unattached from the under-side of the flywheel (a fairly common problem onsome engines). Or the engine has many hours on it,and the timing plate under the flywheel is worn andhas excessive play.

So if no one has tried to adjust your carburetors,and your flywheel isn’t loose, it’s highly unlikely thatyour ignition timing has changed. But if you have anydoubts based on all the information presented here,get your timing professionally checked.

More on the CDI UnitIf your engine has been intermittently quitting or in-termittently losing rpm, there is still a remote possi-bility that your CDI unit is acting up. Unfortunately,

questions with the CDI unit may require you to relyon your dealer’s expertise for some tests, particularlyon mid-sized to larger outboard engines. However,if you have a no-spark condition, and you have care-fully performed all of the tests outlined above, youcan feel quite comfortable purchasing a new CDIunit and installing it. That was your problem.

Other problems with the CDI unit are a little moredifficult to pinpoint. Your system may have a built-in rpm limiter, or a slow-down circuit designed toreduce engine rpm if the engine overheats. If all ofyour other tests point to the CDI unit in anythingother than a no-spark situation, inform your dealer ofeverything you have done and rely on the dealer tomake the final decision on replacing the CDI unit.Dealers will not accept returns on electrical parts, sotrial-and-error methods of testing can be expensive.

Optical-Timing SystemsIf you own a medium-to-large outboard made withinthe last several years, you may have a subsystem inte-grated into your CDI unit called optical timing. This isa very sophisticated system that electronically controlsthe timing advance and retards the spark for easierstarting. Unfortunately, troubleshooting this systemrequires an arsenal of specialized test equipment andadapters. If your engine has an optical timing system,consult your dealer for diagnosis once your problemgoes past checking the fuse, spark plugs and wires,coils, and looking for corroded or loose connections,all of which I described earlier in this chapter.

To sum this section up, remember these impor-tant facts. Most problems with ignition systems willbe visible—a broken wire, a corroded connection,or bad spark plugs that should have been replaced.Also, because of the variety of engines and ignitionsystems, you must use this book together with theservice manual for your engine.

If you follow the guidelines and the simplified testprocedures in this chapter, you’ll be able to pinpointand repair the most common (and some not-so-common) ignition-system problems. If your testslead you to a difficulty that must be handled by thedealer, you’ll have saved the labor dollars you wouldhave spent for the tests.

Tracing and Repairing Starter-Motor Circuits

123

Chapter 8

Here is an all-too-familiar scenario: You wake be-fore dawn, get the old Donzi hooked to the back ofthe station wagon, and are at the launch ramp agood hour before the weekend rush. Half an hourlater she is in the water, tied to the dock, loaded withyour entire family, a few friends, a picnic lunch,beer, soda pop, fishing gear, water skis, two gallonsof SPF 30 sunblock, and the family rottweiler. Therising sun is shining, the birds are singing, the sea isflat calm. In short, it’s the start of a glorious day—aperfect day to spend on the water.

Finally, you’re ready to go. You run the bilgeblowers for a while, then with a captain-like flour-ish you turn the ignition switch—and nothing hap-pens. Suddenly everyone is staring at you and therottweiler is making rumbling noises deep in histhroat. In desperation you try the switch again—stillnothing. Then you check the battery switch, the bat-teries, and all the terminals. They are all OK, but therottweiler’s lip is starting to curl and your passengersare picking up blunt objects as they form a circlearound you. What are you going to do? Well, it’s agood thing you bought this book.

Sooner or later it’s bound to happen. You turnyour ignition key to start the engine, and it wel-comes you with a disheartening click-click sound, orperhaps no sound at all. These classic symptomscould well indicate a starter-motor or starter-circuit problem. Let’s take a look at these symptoms,try to understand what they mean, and then look ata few ways to fix the problem before the rottweilermakes an early brunch of your leg.

Like all problems with electrical circuits dis-cussed in this book, you need to systematically at-tack difficulties with your starter motor and not skipany steps in your diagnosis. Mistakes here can be ex-pensive not only in the cost of replacement parts,but in time spent getting to the starter motor. Boat-builders have an uncanny knack for burying these

important parts in obscure places where you’ll swearyou need arms 10 inches longer than normal toreach them.

Follow the steps I have outlined in this chapter,and you’ll make the correct starting-system diagno-sis every time without fear of unnecessarily replac-ing expensive parts, or of your spouse asking for adivorce.

Coast Guard Regulations for Starter MotorsThe U.S. Coast Guard mandates that, like alterna-tors and distributors, starter motors used on gasoline-powered boats be the ignition-protected typediscussed in chapters 4 and 7. This is serious busi-ness, and an area where I have personally seen morethan one act of foolishness end in catastrophe. A for-mer student of mine owned a small marina that, likemost marinas, did routine service on customers’boats. In a well-intentioned attempt to save a fewdollars for a customer, my student (this happenedlong before he was my student, of course) made thefatal error of installing an automotive starter motorin the customer’s boat. All went well until one day atthe fuel dock, the customer started his boat after afill-up. A large explosion blew the boat to pieces,killing the man.

The insurance investigator for this tragic acci-dent traced the installation of the inappropriatestarter motor to my student. The customer’s wifesued and ended up with a handsome settlement thatincluded my student’s boatyard. He lost everythingas a result of this one act of negligence. The lessonhere is obvious: Do not even consider for a momentthe idea of installing a low-cost automotive startermotor in place of a proper marine one—it couldbe deadly.


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Starter-Motor Problems and SolutionsBecause engine makers all use similar engine blocksand parts, starter-motor circuits have many similar-ities from one brand of engine to another. There-fore, I have been able to develop a generic procedurefor troubleshooting and repairing them. However,the specifics for your boat’s engine can only be foundin your workshop manual. Use the procedures in thischapter as a detailed guide to get you started in theright direction for locating and correcting specificproblems. I will try to direct you to sections of yourworkshop manual when they are needed. The illus-trations that follow show the major parts of the mostcommon starter-motor circuits.

Figure 8-1 shows a typical OMC/Volvo Pentastarter circuit with all the important parts mentionedin the list that follows. Figure 8-2 on page 125 showsa typical MerCruiser starter circuit.

Basic DiagnosticsThere are five basic symptoms of starter-motor andstarter-circuit problems, and basic diagnostics. Let’slook at the symptoms first, and we’ll explore each indetail in the next sections.

� The starter motor is lethargic and turns the en-gine slowly. First check the condition of the bat-

tery and cable connections; then check the engine

and reverse gear assembly to be certain they are not

bound up. If these check out OK, make sure the ca-

ble connections at the starter motor are tight and

clean. Finally, if all the wiring and the engine itself

seem to be in good order, the starter motor itself is

the likely culprit.

� The starter motor turns intermittently. Check

the terminals at the ignition switch, the ignition

switch itself, the neutral safety switch, the engine-

mounted slave solenoid or relay, and finally the

starter motor itself.

� The starter motor doesn’t turn, but the solenoidmakes a clicking sound. Check the battery and

connections, the solenoid, the engine and drive for

seizure, and finally the starter motor itself.

� The starter motor doesn’t turn and the solenoidmakes no clicking sound. Make sure the remote-

shift lever is in neutral; then check the battery and

connections, all fuses and circuit breakers, and the

starter-motor solenoid.

� The starter motor remains engaged and runs withthe engine. Check for a faulty or shorted ignition

switch, a faulty solenoid, or a faulty starter motor.

This list should make it clear that the most com-mon cause of all the starter problems, except for astarter motor that remains engaged with the enginerunning, is found in the battery and cable connec-tions. This cannot be emphasized enough. A battery

Starter MotorSolenoid

CircuitBreakers

StarterRelay

Ignition Switch

Remote Control

Battery

Fig. 8-1. OMC/Volvo Penta starter-motor circuit.

125


weakened by a sticking bilge-pump float switch or alight left on while the boat was unattended for an ex-tended period is a common cause of an engine failingto start. Always be certain your battery is charged toat least 70 percent of its capacity before you assumethat you have starter-motor problems.

If your boat doesn’t have a voltmeter to help youdetermine battery charge, use your multimeter andtake a direct reading of open-circuit voltage at thebattery, using the Open-Circut Voltage versus Stateof Charge table in the Open-Circuit Voltage Test sec-tion on page 84. If your battery is low, you will, ofcourse, have to find out why, and the steps outlinedin chapter 5 will help you to isolate the cause.

Troubleshooting Starter-Motor CircuitsOnce you confirm that the batteries are not thecause of your starter problems, you should begin

troubleshooting. Have the workshop manual closeat hand so you can identify all the circuit compo-nents for your boat.

As a first step, look at all wiring and connectionsto all starter-circuit parts. Tighten any loose partsand terminals, and clean any corroded terminals.Don’t forget to check the fuses and circuit breakers. Ablown fuse or a tripped circuit breaker on a starter-motor circuit could be caused by a partially seizedstarter motor or, in the worst case, a seized engine,both of which situations will be covered in more de-tail later on in this chapter.

If all connections and fuses or breakers appear tobe in good order, a faulty part is certainly the cause foryour starter-circuit grief, and a step-by-step approachwill be needed to determine which part is at fault.

Starter SolenoidMost marine inboard engines have a remote solenoid,sometimes called a slave relay. A solenoid is used asa remote switch to control a circuit, such as yourstarter circuit, that carries heavy amperage. Actingas a shortcut, the solenoid is connected to the starterswitch with a smaller wire to save on the amount ofheavy wiring needed to operate the starter circuit. Inother words, instead of having a cable as big as yourthumb running from the battery to the ignitionswitch and then from the ignition switch to thestarter motor, the heavy cable connects directly to thestarter motor through a solenoid. The solenoid is op-erated by a much smaller (usually 10 or 12 AWG)wire that connects the solenoid to the ignition switch.

Many starter circuits use a solenoid as a remoterelay that does not carry full starter-motor current.To determine if your solenoid is intended to carrystarter-motor current, first locate the solenoid. It’sgenerally cylindrical and is often found on a bracketat the top forward end of the engine. It will have twolarge wires and two small wires attached to it. Look atthe size of the wire on the solenoid terminals. If thelarge wires are the same size as your battery cables(typically 4 AWG or larger), the solenoid carriesstarter-motor current. However, if the large wires aresmaller than the battery cables—around the 12, 10,or 8 AWG range—the solenoid does not carry full

90 AmpFuse

Starter MotorSolenoid

CircuitBreaker

GroundStud

StarterSlaveSolenoid

Battery

Fig. 8-2. Typical MerCruiser starter-motor circuit diagram.

126


starter-motor current. The small wires are usually14 or 12 AWG in both cases.

If you have a medium-to-large boat (over about20 feet) with an inboard engine that does not have aremote solenoid, it will have one mounted on top ofthe starter motor. In this case, it will have only onelarge wire with one end connected to the solenoid andthe other terminal connected directly to the battery orto the battery selector switch.

Solenoid TestTesting a solenoid is really rather simple once youknow what the four wires do. One of the large wireson the solenoid comes from the battery and the othergoes to the starter motor. One of the small wirescomes from the ignition switch, and the other, ifthere is one, connects to ground. Some solenoids aredesigned to ground through the case, and the boltthat attaches it to the engine acts as the ground. Fig-ure 8-3a shows a heavy-duty solenoid; figure 8-3bshows a similar solenoid that does not carry fullstarter-motor current.

To test a solenoid, first make sure that the igni-

tion switch is delivering battery voltage to the sole-noid and that the ground to the engine from the so-lenoid is in good order. You’ll need your multimeterset on the DC volt scale to do all of the following testsexcept the ground-continuity test.

Use your multimeter set to the ohms scale youused for testing continuity to make sure the groundfrom the relay to the engine is in good order. Con-nect one probe to the solenoid terminal with theblack wire (the red probe will be fine, but it doesn’tmatter when checking continuity) and connect theremaining probe to ground. You should have a read-ing of almost zero ohms, and if your multimeter isequipped with a beeper for continuity, it shouldbeep. If you don’t find continuity, clean the terminalsat the relay and engine, then recheck. If the problempersists, install a new ground wire. Figure 8-4 onpage 127 shows the ground being checked with amultimeter.

Once you have verified continuity to ground,check the power lead on the solenoid for battery volt-age. The power lead will almost always be a large redwire, but verify the color on your wiring diagram.

Fig. 8-3a. A heavy-duty remote solenoid. Fig. 8-3b. A light-duty relay.

127


You might need a helper to turn the ignition switchwhile you check the meter. Connect the meter asshown in figure 8-5 with the red probe attached to thered wire and the black probe connected to ground.Next, have your helper turn the ignition switch tostart. If your boat has a starter button separate fromthe ignition switch, turn the key on before pushingthe starter button. Make sure the transmission shifteris in neutral. You should get a reading of approximatebattery voltage as the engine cranks. If you don’t findbattery voltage and the engine won’t crank, there is anopen circuit, which could be caused by a blown fuse,between the ignition switch and the relay.

A third wire on the relay will have battery voltagepresent with the key on. In some cases this terminalwill be hot whenever the battery master switch is on.If not, trace this wire back to its source and repairthe open circuit. Use your wiring diagram to deter-mine where the wire is connected to power.

If battery voltage is present, determine if the re-maining wire on the relay has battery voltage with thekey in the start position. If it does, your starter-circuitproblems have nothing to do with the solenoid or

any of the wires going to it. If it doesn’t, the solenoidis faulty and must be replaced.

Current-Draw TestMeasuring the current drawn by the starter motoras it operates will give you some important infor-mation. However, specifications for the amperagedrawn by different makes and models of engines aredifficult to come by. Manufacturers usually don’tprovide these data even in their workshop manu-als. As a means of estimating current requirementsfor starter motors, mechanics have for years used 1 amp for each cubic inch of engine displacement asa starting point for gasoline engines. Diesel enginesoperate with much higher compression ratios, so adiesel starter motor might draw as much as 2 ampsper cubic inch of displacement. Both these valuesare only good for very rough estimates of starter-motor current. Gear reduction starter motors,which have become increasingly popular in recentyears, typically draw much less current than do direct-drive motors—about half, for a two-to-onereduction ratio.

Fig. 8-4. Using an ohmmeter to check ground continuity atthe solenoid.

Fig. 8-5. Checking for voltage supply to a starter-motor sole-noid. You should get a reading of approximate battery volt-age here.

128


So, if the amperage specifications aren’t availablefrom the engine maker, how do we get them? Easy!Just do a current-draw test when you know yourstarter is working normally and record the amper-age the starter motor uses in your manual. Thenwhen a problem does crop up, you’ll have a knownvalue to work with as a benchmark.

To do the current-draw test, first make sure yourstarting battery is in good, serviceable condition. Ifyou have an inductive-clamp multimeter capable ofmeasuring up to about 500 amps, clamp the induc-tive pickup over the main battery cable going to thestarter motor and take a reading while a helpercranks the engine. Now you have the normal amper-age you can expect your starter motor to draw. If youdon’t have an inductive-pickup multimeter, one ofthe inexpensive Snap-On inductive meters shown inmy tool collection in chapter 1 will do the job.

When you have a starting problem that you thinkmight be caused by the starter motor, first double-check your battery to make sure it’s charged and ingood condition, then repeat the current-draw test. Ifyour new reading is lower than the previously estab-lished benchmark reading, the starting problem isprobably due to loose or corroded terminals in the bat-tery cable connected to the starter motor. If the cablehas been replaced since you established your bench-mark and the terminals are clean and tight, the newcable is probably undersized and needs to be upgraded.

If the reading you get is higher than the bench-mark reading, make sure that the problem is notcaused by a mechanical fault such as a partially seizedengine or a frozen drive unit. You may need to callin a pro to help out at this point. Once you’re cer-tain that the engine is not causing the problem, youcan be sure that any excess current drawn by thestarter motor is due to a fault within the motor. Re-move it and send it out for overhaul.

Voltage-Drop TestAnother useful test for your starter motor andstarter circuit is to trace the circuit while checkingfor voltage drop at various points. This test will beoutlined in the following section on outboard-engine starter circuits and will work just as well forinboard engines.

Outboard-Engine Starter CircuitsA system overview of a typical starter-motor circuiton an outboard engine with remote control is shownin figure 8-6a on page 129. On many engines the re-mote-control harness plug is located under the en-gine cowl, so this plug is not as shown in the diagram.

If your outboard engine doesn’t have a remote ig-nition switch, it will have a starter button located onthe engine, and may have a neutral-safety switch in-tegrated into the mechanical shift linkage under thecowl. A simplified wiring diagram of this circuit isshown in figure 8-6b on page 129. Your engine mayhave some of these connections in a wiring junctionbox. Also, starter-motor battery terminals are oftenused by manufacturers as handy places to attach ad-ditional circuits, so refer to your wiring diagram andnarrow the number of wires down to what you seein this drawing; ignore the rest.

All outboard engines use inertia-type startermotors that engage the flywheel ring-gear whencentrifugal force throws the drive gear upward.Medium-to-large outboard engines also use a re-motely mounted solenoid just like those used on in-board engines. Problems with inertia systems can beas simple as a low battery, or corroded terminalscausing a cranking speed that’s too slow to gener-ate enough inertia to engage the drive gear. So, aswith any system, the first thing to check if troubledevelops is the battery and all its connections.

The open-circuit voltage test described in chap-ter 5 will show you if the battery is fully charged. Ifit isn’t, charge the battery to bring it up to snuff be-fore proceeding with any of the following tests. Ofall the electrical circuits on your boat, the startercircuit is probably the one that draws the most am-perage; until the engine starts, the starter motorneeds all the juice the battery can give it.

After you make sure your battery is fully charged,it’s time to trace circuits. To test the integrated systemfound on small engines without remote control, firstcheck for voltage at points throughout the circuit. Fig-ure 8-6c on page 129 shows the points to check and thesequence in which you should check them. Make sureyour engine ground and the ground bolt or cable (itshould be the black one) are free of corrosion and tight.

129


At point 1, check the power to thepush-button switch. With your meter’sblack probe attached to an engine ground(the bolt or cable grounding the startermotor to the engine is a good point), usethe red probe to check the other pointsalong the circuit. The voltage at point 1should be very nearly the same as your di-rect reading across the battery. If it isn’t,there is a bad wire or broken connectionbetween the battery and the terminal atpoint 1. This test illustrates how batteryvoltage gets to the hot side of the starterbutton, usually via a red wire.

If the voltage is good here, proceed topoint 2. Disable the ignition to preventthe engine from starting as you do thenext four tests. Press the starter buttonwhile holding the red probe to point 2,the output side of the starter button. You should find a reading of approxi-mately 12 volts. If you don’t, your starter button is defective and will need to be re-placed.

Remote control with key switchand neutral safety switch

Remote controlharness plug

Battery,Positive cable

Electricaljunction

Solenoid

Engineground

Startermotor

Battery,groundcable

12 voltBattery

Starter motor,grounded toengine

Neutral safetyswitch

Enginegroundpoint

Starterpushbutton

❷

❸

❹

❺

❶

Enginegroundpoint


Neutral safetyswitch

Starterpushbutton

Fig. 8-6a. A typical outboard-engine starter-motor circuit with remotecontrol.

Fig. 8-6c. Using a voltmeter to check the outboard integratedstarter-motor circuit. Use the voltmeter to check voltage ateach point indicated in the circuit.

Fig. 8-6b. An outboard engine with integrated starter-motorcircuit and no remote control.

130


If you do find 12 volts at point 2, proceed to point3 and connect the red probe to the hot side of theneutral-safety switch, which disconnects the starter-motor when the transmission is in gear. You shouldget another 12-volt reading. If not, the connection isbad or the wire between the starter button and theneutral-safety switch has a break in it. Repair or re-place the wire as needed.

Next, be sure the transmission is in neutral andmove your probe to point 4 (the output side of thesafety switch). Push the button and take a reading;you should get 12 volts. If you don’t, the neutral-safety switch is defective or out of adjustment. Tocheck for proper adjustment, unbolt the switch fromits bracket, allowing the switch button to extendfully. If you still cannot get a 12-volt reading at point4, the switch is bad and must be replaced. If you doget a 12-volt reading, adjust the neutral-safety switchby repositioning it in its mount so that the shift link-age extends the button as far as it will go.

If you do get a 12-volt reading at point 4 and theengine still won’t crank, move the red probe to point5 at the battery terminal on the starter motor (theconnection with the large red wire). With the enginein neutral, press the starter button and check for 12volts. If you don’t find it, there is a poor connectionor a broken wire between points 4 and 5. Repair orreplace the wire as required. If you do find 12 volts

here, the problem is in the starter motor, and it willhave to be removed for rebuilding or replacement.

Voltage-Drop TestAnother simple test that can help you to locate anybad connections, undersized wires, or faulty partsthat could cause excessive resistance and slow-crankcondition in a starter circuit is called the voltage-droptest. This test requires a digital multimeter (you’ll bechecking for readings of 0.3 volt or less) set to thelow-volts scale if it isn’t self-scaling.

The meter connections and the sequence for thevoltage-drop test are shown in figures 8-7a–d. It’s agood idea to get a set of the thread-on alligator-clipprobes (many multimeters now come with inter-changeable probes as standard equipment), availableat Radio Shack and other supply houses that sellmultimeters. The alligator clips let you keep yourprobes attached to a wire or terminal while youcrank the engine and take a reading, eliminating theneed for an extra set of hands.

First check the connections shown as A and B infigure 8-7a. The red wire attached to connection A isfrom the ignition switch or starter button and pro-vides power to the solenoid when the ignition switchor starter button is engaged. The black wire fromconnection B is the ground wire to the coil withinthe solenoid. Make sure that this ground is good.


Enginegroundpoint

Startersolenoid

AB


Enginegroundpoint

Startersolenoid

AB

A B

Figs. 8-7a–d. Sequence of a starter-motor circuit voltage-drop test being performed. Excessive voltage drop at any point in thecircuit indicates a bad connection or possibly wire cabling that’s too small.

131


With the key off, use your multimeter set up to readresistance and check for continuity (a reading ofvery close to zero ohms) between the terminal atconnection B and ground on the engine block. If youdon’t find continuity, repair the connections or re-place the wire.

Next, turn the key to start and check for 12 voltsat the terminal labeled connection A. If 12 volts isnot present, the problem is somewhere in the wirefrom your starter-motor switch or neutral-safetyswitch. Follow the steps described later to correctthis problem. If all seems well here, proceed withthe voltage-drop test.

For each of the four steps to this test, the enginemust be cranking but not firing. In step one, con-nect the meter as shown in figure 8-7a. Your voltagereading with the engine cranking should not exceed0.3 volt. If it does, then the connection at the posi-tive battery post is bad, the connection at the sole-noid is bad, or the battery cable is too small and mustbe upgraded to a larger one. An easy way to checkfor a too-small battery cable is to feel it as you crankthe engine. If it gets warm to the touch, it’s too small.

Step two of the voltage-drop test, as shown in fig-ure 8-7b, is to check the voltage drop through thesolenoid. Connect the meter directly to the twolargest terminals on the solenoid. A reading here inexcess of 0.2 volt indicates a fault inside the solenoid,and it will have to be replaced.

Next connect the voltmeter as shown in figure 8-7c with one lead to the terminal on the output side

of the solenoid and the other to the large positive ter-minal on the starter motor. While cranking the engine, your voltage reading should not exceed 0.2volt. If it does, the connection at the solenoid is bador, as with the battery cables, the wire connecting thesolenoid to the starter motor is too small. (This wireshould be the same size as the main battery cables.) Atoo-small cable would only be a problem if someonechanged the cable before you. Factory wiring is care-fully engineered for size and is never too small. Diffi-culties are caused when improper repairs are made.

Battery Cable Size

Here are a few guidelines for sizing battery cables

�

For engines 15 horsepower and under with a distance ofless than 10 feet (3 meters) to the battery, 10 AWG cableis usually adequate.

�

For runs of 10 to 15 feet (3 to 5 meters), use 8 AWG.�

For runs of 16 to 20 feet (5 to 7 meters), use 6 AWG.�

On engines in the 20-to-30-horsepower range, use 6 AWG, 4 AWG, or 3 AWG, respectively, for the same cable runs.

�

On the larger engines (V4 and V6), use 4 AWG, 2 AWG,and 1 AWG, respectively.


Enginegroundpoint

Startersolenoid

AB


Enginegroundpoint

Starter solenoid

AB

C D

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Finally, connect the meter as shown in figure 8-7don page 131 with one probe connected to the body ofthe starter motor (scrape away a little paint to be sureof a good contact) and the other probe connected tothe negative terminal on the battery. Turn the key tostart. Your voltage reading should be less than 0.3volt. If the reading is higher, either a connection isbad at the engine or at the negative battery post, orthe cable is undersized. (It should also be the samesize as the main battery cables.)

This test will work with any starter circuit, in-board or outboard, and the values for allowable volt-age drop given here apply to all systems using a12-volt power, regardless of engine size. Also, youmay notice that the total voltage drop may exceed the3 percent mentioned earlier in this book. Oddlyenough, the total individual voltage drops may fallsomewhere between the 3 and 10 percent limits discussed.

I have always felt that the 3 percent maximum ismost important for a starter-motor circuit, meaningthat the total voltage drop would be no more than0.36 volt for the entire circuit. Having said that, I cantell you that engine-service manuals consistently usea 0.2-volt maximum drop for all the connections andparts up to the starter motor, and 0.3 volt back tothe battery as the acceptable limit; this gives a maxi-mum of 0.5 volt. The truth is, a well-done factory cir-cuit will give voltage readings well below the 3 percent tolerance, and I prefer to use that figurefor my own criterion. I mention the 0.2- and 0.3-voltspecifications here only because I know you’ll runinto them if you follow your service manual as youshould, when doing these tests.

Testing the Neutral-Safety SwitchIf your boat has remote engine controls, with theshift lever and ignition switch at the helm, the neutral-safety switch is located inside the controlunit. Therefore, you should never attempt to diag-nose problems with this switch without the aid ofthe workshop manual for your engine and controlunit. There are just too many variables in wire color-coding and control-unit disassembly procedures

to cover them all here. In fact, unless you’re fairlyconfident as a mechanic, you should never remove or attempt to disassemble the remote-control unit.It’s full of spring-loaded levers, shims, and cable attachments that are critical in their placement andfunction. So beware!

However, it’s quite easy to check all wiring andparts affected by the neutral-safety switch, enablingyou to consult intelligently about the problem withyour mechanic.

Your neutral-safety switch is electrically con-nected to both your ignition switch and the startersolenoid. When you shift into neutral, the switchshould close, completing the circuit between the ig-nition switch and the terminal marked connection A,shown in figure 8-7a on page 130. The wire on thisterminal connects the solenoid to the ignition switchand should be identified in your wiring diagram. Thequick check to see if the switch is functioning is tolook for a 12-volt reading at this terminal with thekey on start. Simply connect your meter with theblack probe to ground and the red probe to this ter-minal, and have someone shift into neutral and turnthe key to start. If you get no reading when the key isturned to start, the problem is probably within thecontrol unit, but not necessarily.

There could be corrosion at the remote-controlmaster plug, or there could be a break in the wireconnecting the plug assembly to the back of the boat.Using your wiring diagram as a guide, identify thissolenoid feed wire. Next, disconnect the wire fromthe solenoid and identify which terminal it goes toin the plug assembly. With your multimeter set to thelow-ohms scale, check for continuity between thesetwo points. (Using your alligator clips, you may wantto make an extended jumper lead to one of the testleads from your meter, depending on the distancebetween the plug assembly and the solenoid.) Youshould get a reading of nearly zero ohms if this wireis intact from the plug to the engine.

If you get a high reading or a reading of infinity,there is a break in the wire or a corroded connec-tion between the plug and the engine. In some cases,this will mean replacing the extension harness as aunit. If the wire from the control unit to the solenoid

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is a series of individual wires wrapped in electricaltape or plastic tie-wraps, you should be able to tracethe harness and find the break. Repair or replace thewire as required. If you get a resistance reading nearzero, showing continuity, the problem is within theremote-control unit and must be fixed by yourdealer.

Figure 8-8 shows the extension harness beingtested with a multimeter.

Testing for neutral-safety switch maladjustmentis quite simple. Hold the shift-control lever withone hand and the ignition key with the other. Holdthe key in the start position and gently work theshift lever to its extremes in the neutral position.(Never try to shift into gear without the engine run-ning; you could damage to your shift mechanism.)If you hear the starter motor try to engage, then theswitch is out of adjustment or the remote-controlmechanism is badly worn and will need to be serviced by your dealer. Don’t be surprised if thecontrol mechanism needs to be replaced due to excessive wear of the internal parts. This is not un-common on older units.

Engine Ignition SwitchLike the neutral-safety switch, most ignition switchesare located inside the remote-control unit describedabove. This makes testing difficult, but some of thesame procedures you used to test the neutral-safetyswitch also apply to the ignition switch. Essentially,you’re testing for battery voltage at the switch and forcontinuity to the solenoid. This can be done outsidethe remote-control unit up to the main plug assem-bly on the control unit. If the wiring harness con-necting the engine to the remote-control unit is ingood condition, which can be checked visually bytracing it from the engine up under the coaming ofthe boat to the control unit, problems are probablywithin the remote-control unit.

All manufacturers provide good, functional de-scriptions of each terminal in the wiring-harness plug,and all provide a test sequence to verify continuity between the terminals on this plug with the ignitionswitch in different positions. However, a good quickcheck of these terminals can also be made using yourmultimeter.

Fig. 8-8. Checking the wiring harness for continuity between the remote control and the engine. In this picture I’ve discon-nected the plug at the back of the ignition switch and at the engine, and am using my ohmmeter to check for breaks in thewiring harness.

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First verify that you have 12 volts at the ignitionswitch. Use your wiring diagram to identify thepower lead from the engine to the main plug on theengine side of the circuit. (This wire is usually fed bya jumper lead that comes from the starter-motor so-lenoid or from a junction box bolted to the side ofthe engine block.) This terminal will generally bemuch larger than the others. If you find 12 volts atthis plug and the plug terminals are in good condi-tion, it’s reasonable to assume that 12 volts is gettingto the remote-control assembly and feeding the ig-nition switch.

In all cases there will be a wire coming from theremote-control assembly that provides 12 volts to theignition module (CDI unit) on your engine. Thiswire activates the electronic circuitry within themodule while the engine is running. Use your wiringdiagram to identify this wire on your engine. Makesure the emergency-shutoff switch is off, and turnon the ignition key. A reading of 12 volts where this

wire attaches to the ignition module tells you thatthis function of the ignition switch is OK. If youdon’t get 12 volts here, you need to trace the mainharness and look for any trouble spots; correct themas needed.

If no trouble spots are found, the problem is inthe remote-control unit. A possible trouble spotcould be the point where you drilled a hole throughthe harness when you were mounting that new rodholder or downrigger.

In addition to 12 volts at the ignition modulewhen the key is turned to start and the shift in neu-tral, you’ll also need 12 volts at one of the small ter-minals on the solenoid. All manufacturers use acolor-coded wire for this connection. (OMC andMercury use a yellow-and-red one.) Remember thatthe black wire from the solenoid is a ground wireand not the one to check. Use the test described ear-lier to check for voltage at this point. If 12 volts isfound while the key is in start, you know that the ig-

Fig. 8-9a. Checking voltage supply to an outboard-enginesolenoid with the key in the start position. Remember, withthe key in the start position, if the engine is cranking, thevoltage reading will drop down to as little as about 9.6 volts.

Fig. 8-9b. Checking voltage at the outboard solenoid withthe key in the “on” position. With this test, you should get areading near battery voltage.

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nition switch is OK. If you don’t find 12 volts here,trace the harness as for the other wires. If no dam-age can be found, the problem is inside the controlbox.

Figure 8-9a on page 134 shows the solenoid ter-minal being checked for 12 volts with the ignitionswitch in start. Figure 8-9b on page 134 shows thepositive wire to the starter solenoid being checkedfor 12 volts with the ignition switch on.

Other Outboard-Engine Starter-Motor ProblemsIn addition to slow starting or no starting, some se-vere mechanical problems may also cause a no-startcondition. The possibility of extreme engine over-heating and water getting inside your engine is real.The symptom for either condition is a loud “clunk”

as the starter-motor drive gear engages the flywheel,only to encounter an engine that will not turn over.In the case of a manual-start motor, the pull cordsimply won’t budge more than several inches as youpull with all your might. If either of these deadlysymptoms is present, you have an internal engineproblem that goes beyond the scope of this book.

For a solution to these and most other outboard-engine problems, I strongly recommend my book,Outboard Engines: Maintenance, Troubleshooting, andRepair.

This concludes the starter-motor section of thisbook. By following the tips and guidelines here, youshould be able to trace your way through just aboutany starter-motor and starter-circuit problems youencounter, and keep your boat on the water insteadof in the shop.

Installing your own electrical equipment is not onlya rewarding personal accomplishment, it can alsosave you a lot of hard-earned money. If you boughta new boat, it may have come with a long list of op-tional extras—probably a VHF radio and a fish-finder, and maybe a chart plotter and radar. If youbought a used boat, the previous owner undoubt-edly added an assortment of electronic and electricalgadgetry to the list. However, no matter how wellequipped your new or used boat may be, you’lleventually want to make some modifications to theelectrical system. Sooner or later you’ll want to adda new light fixture, an upgraded battery charger, abetter VHF radio, or an extra bilge pump. By fol-lowing my recommendations and advice in thischapter, even a novice electrician can easily install allthese things and many more.

Before You BeginBefore installing any new electrical accessory, thereare some important things to consider. Among themost important are the voltage and amperage thatwill be required by the new item. However, youmust also think about the capacity of your distribu-tion panel, the fuse or circuit breaker you’re going touse, and the size of the wire and how you’re goingto run it.

Voltage RequirementsYou must be sure that the accessory, whatever it maybe, is designed to operate at the system voltage inyour boat. Most small to medium-sized powerboatstoday operate with 12-volt electrical systems. Largerboats, however, may have 24-volt or even 32-voltsystems. Some even have systems that combine volt-ages, with certain items running at 12 volts and oth-ers running at 24 volts. Higher voltages are used onlarger boats because the higher voltage is more effi-cient and the builder can reduce the size of the

wiring and many parts. (A 24-volt starter motor ismuch smaller and lighter than an equivalent 12-voltstarter motor, for example.)

With higher voltage, wiring ampacity goes up asvoltage increases. This not only saves money butalso considerable weight, and the smaller wire is eas-ier to work with. If you recall from Ohm’s law, aswe discussed in chapter 1, there is a direct and lin-ear trade-off between amperage and voltage. Thismeans that an anchor winch using 80 amps with a12-volt system only needs 40 amps to do the sameamount of work with a 24-volt system. On a 40-footboat with a 70-foot wiring run from the battery tothe winch and back to the battery, this means thebuilder can use a 1/0 AWG cable instead of a 2/0AWG cable. Using West Marine 2006 prices, thebuilder saves nearly $125 just in the cost of the cable;plus, all the components are smaller and lighter andeasier to install.

When you buy a new piece of equipment to in-stall on your boat, the manufacturer will always pro-vide the voltage required to operate the equipment.It will be printed in the installation instructions oron the equipment itself, and sometimes in bothplaces. Before you begin installing your new gadget,double-check to make sure you have one with theright voltage. All the following assumes you’re work-ing on a boat with a 12-volt system.

Amperage RequirementsThe next important specification is the expected am-perage the appliance needs to operate efficiently.Again, the packaging should provide this importantinformation and will often recommend the fuse orcircuit-breaker rating as well. Sometimes the ratedvoltage, amperage, or wattage is also embossed onthe equipment, but not always. Wherever you getthe numbers, a consideration of the amperage andvoltage should always be the first step in selectingthe appropriate wire gauge to use on the new circuit.

Installing Your Own DC Accessories

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Chapter 9


Length of WireNext, you should measure the wiring run from thedistribution panel to the accessory and back to thepanel. Don’t just measure a straight line from the dis-tribution panel to the location of the new accessoryand back again. Make sure you measure the actualroute the wire will follow. It isn’t at all unusual forthe actual route of the wire to be double the straight-line distance or even more.

Voltage Drop and Wire SizeRemember that the longer the run, the higher thepotential voltage drop in your new circuit will beand the larger the wire you’ll need to overcome it.Before you continue, decide now the extent of thevoltage drop you’re willing to accept. Rememberthat the ABYC standards recommend no more thana 3 percent drop for any critical gear such as elec-tronic navigation and communication equipment.However, a new cabin light could fall into the 10percent category.

Personally, I use the 3 percent standard in allcases. Boatbuilders of high-end boats usually use the3 percent standard throughout their new boats.However, high-volume, price-conscious builders willoften use the 10 percent maximum just to savemoney, which is how they can offer their productsat affordable prices. Many noncritical accessories willwork just fine with the higher voltage drop, but oth-ers will suffer reduced performance. Interior lighting,for example, will function at the 10 percent maxi-mum voltage drop but with a considerable loss inlight intensity for a given bulb wattage.

Use the charts provided in chapter 4 to help youthrough this decision on voltage drop and wire size.My recommendation is that unless you’re on a verytight budget, you follow the example of the high-endbuilders and use a 3 percent voltage drop for every-thing. You can’t go wrong.

Wire TypeOnce you have determined the gauge of the wireyou’ll need in your new circuit, think about the wireinsulation requirements and again refer to chapter 4for help determining what’s required.

A time-saving alternative to running separatewires for the hot and ground sides of your new pieceof equipment is quality marine-grade duplex wirethat has the two conductors bonded together muchlike a household extension cord. (Household wire,of course, should never be used on a boat; the insu-lation is not rated for the marine environment.) Du-plex wire has a double layer of insulation, and it’smuch easier to fish through small holes and tightplaces than individual wires. A single run of duplexwire is slightly more expensive than a double run ofsingle wires but usually not enough to offset the con-venience and other advantages it offers.

If you’re trying to match ABYC color-coding rec-ommendations, you might have trouble finding du-plex with the correct colors for the circuits you’reworking with. Be diligent; the better vendors stockthe common colors, and they can order other colorsfor you. They may ask you to order an entire roll,though, which may not be practical in some cases. Ifyou can’t find the colors you want, use the alternativemethods for labeling wires I discussed in chapter 4.

Fuses and Circuit BreakersOnce your wiring has been selected, you must selectthe appropriate fuse or circuit breaker for your newcircuit. This can be a little tricky. Remember that thecircuit protection may be rated to as much as 150percent of the amperage-handling capacity of thesmallest wire in the circuit. This means that if youconnect a new accessory with a continuous draw of5 amps, you would use a fuse or breaker rated notnecessarily at 150 percent of 5 amps (7.5 amps), butrather at 150 percent of the wiring capacity. Let’s takea closer look at this problem.

The wire must be rated at the engine-room spec-ification if any length of the wire goes through thisspace, regardless of length. Keep in mind that the fol-lowing ampacity figures are for wire with an insula-tion rating of 105°C, which is the most common typefound in marine supply houses.

If your new 12-volt accessory were going to bemounted 10 feet away from your boat’s main distri-bution panel (measured along the wiring), youwould have a total run of 20 feet. Using the 3 percent

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voltage-drop criterion and referring to figure 4-3 onpage 44, you can see that the correct wire to use is14 AWG. By using the ampacity table, figure 4-7 onpage 48, you can see that 14 AWG wire has an am-pacity of 35 amps outside the engine room, and justunder 30 amps inside the engine room.

Well, in this example, even though the actualload is only 5 amps, we have connected the load to awire with a base ampacity of, let’s say, 30 amps(we’ll use the engine-room rating here). We coulduse a circuit breaker or fuse rated as high as 45 amps(150 percent of 30) and provide adequate protec-tion for the circuit’s wiring. However, we don’tneed that much protection, and in this case a com-mon 10-amp breaker or fuse would be quite ap-propriate and would provide safe, conservativeprotection for the circuit. Remember, when in-stalling overcurrent protection, it’s the circuitwiring you’re protecting. Any protection for theequipment the circuit is supplying will be done atthe equipment (with the exception of motor loadsas discussed in chapter 4), which may be internallyprotected, but in fact usually is protected by a fuseor breaker in the circuitry.

This explains why most electronic equipment hasan individual fuse in addition to the fuse or circuitbreaker on the circuit. The main fuse or circuitbreaker on each circuit is there to protect the wiringthat’s common to all equipment on the circuit, andthe internal fuse is there to protect each individualpiece of equipment. If, in the example above, therewere two other pieces of equipment sharing the cir-cuit with our 5-amp device, one drawing 1 amp andanother drawing 2 amps, you would have a total of 8amps on the circuit. You could then have the 10-ampmain fuse or circuit breaker for the wiring and threeindividual fuses of 5, 2, and 1 amp each to protect theequipment.

Panel Feed WireAn additional consideration, especially if you’re go-ing to be adding heavier loads or multiple addi-tional loads to your distribution panel, is the sizeof the wire and the rating of any circuit breakers orfuses feeding the distribution panel. Keep in mind

that the builder may have based the size of the positive and ground wires to the panel only on the factory-installed equipment, even though the panelmay have blank sockets where additional breakersand circuits could be added.

Distribution-panel ratings are based on the sumof the ratings of all the circuit breakers installed onthe panel. The ampacity of the conductors feedingthe panel must match that total amperage. Thus, apanel with two 20-amp breakers, five 10-amp break-ers, and five 5-amp breakers (not an uncommonarrangement) would need a master circuit breakeror fuse and a feed wire that could handle 115 ampsif everything on the boat were turned on at once.

The ABYC also says that if the panel has a mastercircuit breaker (on the panel) rated at no more than100 percent of the total rating of all the breakers onthe panel, the conductors feeding the panel can beprotected at up to 150 percent of the amperage ofthe feed conductors. If the main panel has no mastercircuit breaker, the fuse or circuit breaker for the feedwire may not be rated at more than 100 percent ofthe conductor ampacity. This means that you mustbe sure the breaker protection and the wire size areappropriate for any additional circuits you decide towire into the existing distribution panel on yourboat. To determine if a wiring upgrade feeding yourpanel is needed, get the AWG size for the positivefeed and DC negative (ground) lead from the insu-lation, and use the ampacity table in figure 4-7 to seeif you need to make any changes.

Color-Coding and Wiring DiagramAny wiring you add to your boat needs to be properlyidentified. Color coding, in accordance with theABYC standards, can help identify the function of in-dividual wires, but you should also draw up a wiringdiagram of the circuit you’ve added and put it withthe other paperwork in your boat’s informationpackage. If you already have a master wiring diagram,making an addendum to it now will make life a loteasier three seasons down the waterway when thenew circuit starts to act up. For a list of recommen-dations on alternate wire identification, refer tochapter 4.

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Once you deal with all of the above, you’re readyto install your own DC accessories. Some commonadditions follow, with my personal step-by-step ap-proach to installing each accessory outlined. After re-viewing these examples, you should be ready for justabout any circuit you may wish to add to your boat.

Installing a New Cabin LightIf you’re installing a conventional incandescent lightor one of the newer halogen lights, don’t worryabout polarity. These light bulbs really don’t carewhich way the electricity flows through them. Ifyou’re adding a low-voltage fluorescent fixture,however, you’ll have to observe any positive or neg-ative wiring indicated by the manufacturer. Circuitswith dimmer switches (rheostats) and light-emittingdiodes (LEDs), which are commonly used in instru-ment lighting and are even available now as replace-ments for conventional low-voltage light bulbs, arealso sensitive to polarity.

Some of the companies that make light fixturesrecommend the correct fuse to use and the appro-priate wire gauge based on the length of the wire run.If you don’t have these specifications, you must fig-ure these numbers out for yourself. The packagingshould at least tell you the operating voltage of thebulb in the fixture, so you’ll have at least one of theneeded values. Also, the wattage will be given withmost light fixtures. By using the wattage equationfrom chapter 1, you can easily calculate the amperageby dividing the wattage by the voltage. The result willbe the amperage the fixture will need. For example,a 20-watt bulb on a 12-volt circuit will draw 1.7 amps(20 ÷ 12 = 1.7).

Once the amperage is known, measure the dis-tance of the run from the distribution panel to thenew fixture and back again. A quick reference to thetable will give you the wire size to use for the job.Since this is a cabin light, you should use a dark bluewire to the light and a black or yellow (preferably yel-low) wire for the return to the panel.

One precaution regarding fixtures of this type:Often a manufacturer provides a short length of wirelead from the fixture to facilitate attachment to your

wiring harness or new circuit. Typically these leadswill be 16 AWG. Regardless of which gauge wire youselect to run from your distribution panel to the newfixture, you must always rate the circuit overcurrentprotection at the ampacity of the smallest wire in thecircuit. In this example it would be the 16 AWG wiresupplied with the fixture, assuming you use a 14AWG feeder and ground return wire for a long run.

Step-by-Step InstructionsSo, with the basics above in mind, my step-by-stepapproach to adding a new cabin light looks like this:

1. After selecting a light fixture you like and mak-ing sure that the voltage is the same as it is onyour boat, find the wattage of the bulb.

2. Once the wattage is known, determine the am-perage requirements for the fixture. In the aboveexample, a 12-volt, 20-watt bulb would require1.7 amps. Always round up, so in this case theamperage requirements would be 2 amps.

3. Use the table of wire gauges in figure 4-3 on page44 for acceptable voltage drop and length of wirerun. If the amperage requirements are less thanthe minimum specified on the table, use thegauge indicated for the minimum value (5amps). In any event, never use wire smaller than16 AWG when adding anything to your boat, nomatter how little current is drawn by the equip-ment you’re installing. Wire smaller than 16AWG is only used for electronic control circuitsand small connecting links on the back of instru-ment panels and the like.

4. Select the switch or circuit breaker on the distrib-ution panel you’ll be using to feed this new circuit.

5. Determine that the amperage rating of the fuseor circuit breaker is appropriate for the total ofall circuits or loads being fed by that breaker. Forexample: In this case you may already be servic-ing several cabin lights in addition to the oneyou’re adding. Total circuit protection at thepanel must cover the amperage of all the lightson any given circuit. The fuse or circuit breakermust not be rated at more than 150 percent ofthe ampacity of the smallest wire used, which

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could well be the pigtail on the back of the fix-ture, not the feed wire.

6. Check the total load on the distribution panel,and if the wire and circuit protection on the panelare not large enough, change them to a larger sizebefore doing anything else.

7. Once wire gauge and circuit protection ratings aredetermined, string the wire from the distributionpanel to the location of your new cabin light.Don’t forget to support your new wiring at leastevery 18 inches, and preferably more frequentlythan that. If the wire must go through an areawhere chafe protection is needed, provide it asshown in figure 4-20 on page 59.

8. Connect the ground wire from your new light tothe negative bus bar on the back of the distribu-tion panel and the positive wire to the switch orcircuit breaker output terminal. You might need atwo-to-one connector to tie into a breaker or fuseon the panel.

9. At the fixture end of the wire, use crimp-typebutt connectors to attach the new light to thefeeder wires. If the wire on light-fixture pigtails ismore than two AWG sizes apart, use one of thenew-style step-down butt connectors availablethrough West Marine or any good electrical sup-ply house.

10. Finally, flip on the switch. Is there light? If so,your new circuit is a success. Mount your new fix-ture in position and enjoy.

Figure 9-1 provides a wiring diagram showingwhat your new light circuit might look like in a typi-cal installation. (Individual switches are not illus-trated at the light fixtures.)

Installing a New Bilge PumpTo install a new bilge pump, first establish the gph(gallons per hour) rating of the pump you’ll needbased on the volume of the area the pump will ser-vice, the height from the base of the pump to thepoint of discharge, and other factors.

With bilge pumps, depending upon several vari-ables, the actual amount of bilge water the thing willmove overboard will vary considerably from the rat-ing embossed on the pump. Aside from mechanicalvariations in pumps, you’ll need a circuit with a 3percent maximum voltage drop if you’re going to getanything close to the rated output of the pump. Ex-cess voltage drop here will affect pump motor speedand the volume of water it will move.

According to the ABYC and the chart in figure 2-5 on page 16, a bilge-pump circuit should have abrown positive wire, and either a black or a yellowground-return wire is acceptable.

Because this load is a 12-volt motor, the bilgepump must be protected with a fuse rated at nohigher than the manufacturer’s recommendation. Inmy own tests, I have experimented with fuses as lit-tle as 1.5 amps over the rating recommended by thepump manufacturer. In these tests I locked the

pump’s impeller to simulate anactual installation and let thepump run. Figure 9-2 on page 141is a photograph of the result ofone test. As you can clearly see,the body of the pump is meltedaway and badly deformed. Thewires feeding the pump, on theother hand, are unscathed.

Why does this happen? Why isthe pump itself destroyed, generat-ing enough heat to torch the boatwhile the wires remain intact?When a motor seizes, it works


DCDC

Fig. 9-1. Simplified wiring diagram of a cabin light circuit.

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against the seized impeller and heat builds up withinthe motor windings. As the motor heats, the internalresistance increases and the current flowing throughthe circuit feeding the motor actually decreases. Youcan see how this works by using Ohm’s law and swap-ping around some numbers. If source voltage staysthe same and resistance goes up, amperage goesdown. In this case, the amperage decreases to less thanthe rating of the fuse. Both the wiring and the fuseremain intact, but current will continue to flow tothe motor until it destroys itself. Therefore, neverchange the fuse on a bilge pump or any other motorcircuit for one with a higher amperage rating thanwhat is recommended by the manufacturer.

Do you remember from chapter 4 that a slow-blow fuse is often used in motor circuits? These ac-commodate the very high start-up amperage used byelectrical motors. Check the manufacturer’s recom-mendations for all motor circuits on board yourboat, and have the appropriate spare fuses in yourspares kit. Installing just any old fuse on a motor cir-cuit could be an especially bad move. It could literallycause a meltdown of the motor as well as a lot of un-necessary correspondence between you and your in-surance company.

Now that you have determined the gauge of wireand the size of the fuse you’ll need for your newbilge-pump circuit, remember that the insulation ofthe wire should be moisture-, fuel-, and oil-resistantin case a spill or leak ends up in the bilge. Not thatyou’d pump the spill out with the bilge pump, ofcourse, but the reason for this precaution is so thatwhile you’re removing the oil by other means youwon’t damage the wiring to the pump.

Next, remember that any wire terminals exposedto bilge water require a waterproof connection. Agood choice for joining wires in the bilge or in otherwet areas is the new crimp-type connectors that havea sealing heat-shrink jacket, as shown in figure 9-3.

Securing the WiresTo remain in compliance with the ABYC standards,secure the newly installed bilge-pump wires at a min-imum of 18-inch intervals. The truth is that this stan-dard is quite lenient, and most quality builders securetheir wiring at 4- to 6-inch intervals.

Good choices for securing your wiring are the “p”clips or screw-footed tie-wraps, available at any ma-rine supply house. Look through the selection at agood electrical supply retailer, and you’ll find a mul-titude of ingenious options for keeping your wireswhere you want them.

Fig. 9-2. Melted bilge pump, caused by installing a fuse thatwas overrated for the motor. Notice that the wiring survivedunscathed.

Fig. 9-3. Heat-shrink-type crimp connectors. These are ex-pensive, but worth every penny if you can get your hands onthem.

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Dedicated Bilge-Pump Switch PanelsNow that you’ve got some of the basic supplies assembled, decide if you want to tie this new cir-cuit into the distribution panel or connect it di-rectly to one of your batteries with an optional,dedicated bilge-pump switch panel, as shown in fig-ure 9-4. These switch panels offer an integral fuseand a choice of manual or automatic operation.The better units (as shown) also have a pilot lightthat lights up when the circuit is on. Be careful here,though: I have found many of these switch panelswith 10-amp fuses installed in the holder. If youhave one of the smaller pumps, this is a problem;they often require as little as a 1.5-amp fuse. A 10-amp fuse would never do for a pump with a lockedrotor; the fuse would surely allow the pump to burnup. Always double-check the fuse rating when in-stalling one of these switch panels.

Although the bilge-pump switch panel describedabove could be made from various off-the-shelf com-ponents by a boatowner who had the inclination andtime to do it, these assemblies are so reasonablypriced that I generally use the standard switchpanel—after making sure the fuse is adequate, ofcourse.

Connecting the Pump to PowerThere are several points to consider as you determinewhere you want to connect your new bilge pump to apower supply. If you connect it to the main distribu-tion panel, the pump will be off when the masterswitch is thrown. This might be fine for a boat on atrailer, but less so for one kept at the dock or on amooring where the pump needs to be on while every-thing else is off.

Often pumps are connected directly to the battery and fed through a dedicated switch panel(described above), but loading up a series of connections directly to the battery is simply notgood practice. The ABYC suggests that no morethan four conductors be attached to any one termi-nal. If your battery has a stud-type battery post,you’ll be limited by that restriction. Also, locatingfuses near the battery is a mistake due to the poten-tial accumulation of corrosive vapors near the bat-teries. The resulting corrosion of the fuse and fuseholder can cause excessive voltage drop and all theproblems associated with it.

I’m not suggesting that you not attach your newpump directly to the battery—it is often the best op-tion—but if you do, use the ABYC standard to youradvantage. You can mount the fuse as far as 72 inchesaway from the battery (as long as the wiring issheathed in addition to its insulation) and still be incompliance with the standard.

Another option is to use a single appropriatelysized wire to feed an auxiliary fuse panel connectingall the onboard equipment you want, feeding directlyfrom the battery rather than through the main distri-bution panel. Locate it far enough away from the bat-tery to avoid the corrosive fumes but close enoughto comply with the ABYC standard. Companies likeAncor, Newmar, and Blue Sea Systems make per-fectly suitable fuse panels for this purpose.

Automatic Float SwitchOnce you’ve decided how you’re going to providepower to your new circuit, you need to decide if youwant to install an automatic float switch for your newpump. Since most installations do use an automaticfloat switch of some type, I’ll illustrate that setup here.Fig. 9-4. Bilge-pump master switch panel.

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Figure 9-5 shows the basic parts to this new cir-cuit laid out and ready for the installation of thepump and the switch.

ToolsTools you’ll need for this installation will include thefollowing, some of which are assembled in figure 9-6:

� a wire cutter, a wire stripper, and a set of quality

crimping pliers (described in chapter 1)

� a heat source for shrinking the heat-shrink tubing

(a Bic lighter will do the job, but a heat gun is bet-

ter, and safer)

� slotted and Phillips-head screwdrivers to match the

screws you’ll use to mount the panel, float switch,

and pump assembly

� an electric drill with an assortment of drill bits

� a small saw—either a hole saw or an electric jigsaw,

depending on how you decide to mount your mas-

ter switch—to cut out a hole for the switch panel

Last, but certainly not least, you’ll need a wiringdiagram to help you lay out your new bilge-pumpcircuit. All of the major manufacturers of bilgepumps and switch panels supply this vital informa-tion as part of their installation instructions. They’lloften include a recommended wire gauge to use fora certain length of wire run, saving one step in the in-stallation process. However, I have noticed that therecommended wire size provided by some manufac-

turers of bilge pumps tends to be larger than what isallowed by the sizing chart in figure 4-7. My advicehere is clear: for warranty and liability reasons as wellas your own peace of mind, whenever there is a dis-agreement or conflict among different sources of in-formation, always go with the recommendations ofthe manufacturer, even if it seems like overkill. Re-member, a wire that is too heavy will never do anyharm (up to a reasonable point, of course), whereas awire that’s too small can destroy your boat.

Figure 9-7 shows the diagram that comes with apopular pump assembly available from Rule Industries.

The pump motor shown here is, like most bilgepumps, polarity sensitive. Reversing the positive andground return wires on the pump motor will causethe pump to run backwards. Most bilge pumps (but

Fig 9 - 7Battery Bilge Pump

Float Switch

Panel Switch

Fig. 9-5. Basic circuit components. Fig. 9-7. Wiring diagram for a bilge pump.

Fig. 9-6. Electrical tools needed for a bilge-pump installa-tion.

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not all) are of the centrifugal type, and correct im-peller rotation is imperative if the pump is to workproperly.

Adding a New Compact-Disc PlayerA new CD player, like any other electronic equip-ment you decide to install or add to your boat’s inventory of goodies, is a prime example of equip-ment that is polarity sensitive. Essentially, motorsand any equipment that contains any type of solid-state circuitry all fall into this category. It pays tobe quite cautious here, as mixing the positive andnegative conductors can burn out internal compo-nents of valuable equipment quicker than you cansnap your fingers.

Having said that, the rest of the installation of aCD player is relatively easy, especially if you havefound the above descriptions of the installation of thecabin light and bilge pump easy to understand.

Really, the most difficult part of installing a CDplayer is figuring out where you want to mount it andcutting the hole in the panel for the face plate. Someelectronic equipment today will have a heat sinkmounted on the back chassis, as shown in figure 9-8.This heat sink does just what the name implies; it ra-diates heat away from the parts within the equipmentit’s designed to protect. Make sure that the airflowpast this heat sink is adequate to provide necessarycooling when the equipment is in use. Proper cooling

of the equipment will improve its longevity and per-formance. How much cooling air is enough? Notmuch; just don’t stuff your valuable CD player intoa tiny hole with no room for air to circulate.

Once you decide on a good location for your newCD player and cut the necessary mounting holes,you’re ready to wire it in. I’m sure you rememberedto check the packaging before you left the store afterbuying the player. Quite often the installation in-structions include a template for the mountingcutout. Having this template will save a lot of timeand ensure that you get a proper installation with aminimum of fitting.

As with any electrical equipment, always followthe fuse recommendations provided by the manufac-turer. Most CD players come with a two-wire harnessabout 18 to 24 inches long with an in-line fuse holderalready installed on the power lead. Typically, theseleads are made with 16 AWG wire. Since most suchequipment (but not all) draws less than about 1.5amps, 16 AWG is usually large enough for runs ofup to 30 feet (where the CD player is located 15 feetaway from the power source). If the distance fromthe power goes over 15 feet, step up to 14 AWG.

In this example, using the 3 percent voltage dropfrom chapter 4 for a circuit length of 30 feet, 1.5amps falls below the 5-amp minimum column infigure 4-3 on page 44. Remember to always roundup in wire size and use the 5-amp column calling fora 12 AWG wire for a 30-foot run. As soon as youmove over to the 40-foot column, the table calls for10 AWG wire. If the run were, say, 32 feet I wouldstick to the 12 AWG, because you have alreadyrounded up once.

Also, remember that safety-related electronicequipment will always fall into the 3 percent voltage-drop category for wire sizing. Much of this equipment(particularly fish-finders, but other gear as well) is designed to work in a fairly narrow voltage range. (Seechapter 12 for more details on this subject.)

Your new CD player should be tied into yourmain distribution panel just like the cabin light already discussed. Since it falls into the general-equipment category, the use of duplex wire with redand black or red and yellow wires will keep the feedFig. 9-8. Typical electronic equipment heat sink.

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wire in compliance with the ABYC’s color-codingscheme.

A 10-amp circuit breaker or fuse at the panel willbe a good choice here as long as the manufacturer-supplied fuse and holder are not removed from thecircuit. Remember that the panel fuse will protect thewiring to the CD player, and in the case of 16 AWGwire, the basic ampacity for 105°C-rated wire (themost common) is 25 amps, so a main breaker ratedat 10 amps is safe and, in fact, conservative.

Since the factory-supplied harness that came withthe CD player probably came with quick-disconnectbullet-type connectors, you can use the same type tosplice into the harness you’re running from the panelto the player. These bullet-type connectors come inmale and female halves, and are a good way to ensurethat the polarity of the equipment is observed. Justmake sure the correct connector ends up on the ap-propriate wire.

Many installers cut off these bullet connectors andreplace them with straight butt-type crimp connec-tors, feeling that these might be less likely to corrode.The truth is that this is not such a great idea, for sev-eral reasons. First, the standard male and female bul-let connectors enable a quick disconnect in the eventyou need to remove the CD player for service or what-ever reason, and the connector can be reused whenyou reinstall it. Second, most bullet connectors thatI’ve seen have a rubber seal to minimize water intru-sion. Last, these connectors are a good way to ensurethat polarity is observed, regardless of wiring color.

Figure 9-9 shows the bullet-type plug connectorin question.

For the installation of the wire for your new CDplayer, follow the same ten steps for installing thecabin light, and you’ll be ready to go with the mainwiring for the player. (Review the Step-by-Step In-structions earlier in this chapter.)

Keep in mind that many pieces of electronic equip-ment today will have two positive feed wires, oneswitched and the other intended to supply a constantDC current. This is to maintain any internal memorythe equipment may have for such things as preselectedradio stations. So when selecting your power for thememory function on your player (if needed—check

your owner’s manual), remember that this connectionmust be live at all times, and probably the best sourceof power will be at the feed side of your main batteryswitch or at the battery itself.

Adding SpeakersWhen it’s time to connect the speakers for yournewly installed CD player, regular speaker wire,available from Radio Shack and other stereo-supplyhouses, will do the job. However, because of the bet-ter insulation, a better choice would be the marine-grade duplex wire already mentioned.

The ABYC doesn’t address speaker wires in itscolor-coding scheme, so select duplex wires with dif-ferent color schemes to help identify left and rightspeaker leads. When running these leads, rememberto observe polarity, and don’t mix up the wires. Aswith any wiring on board, speaker wires should besupported at least every 18 inches.

Once wire gauge and circuit protection decisionshave been made, the six-step list that follows willguide you through the installation of the CD playerand speakers. Remember that when locating thespeakers, the magnets contained within them will af-fect things like compasses and any electronic com-pass sensors you may have on board. Keep thespeakers at least 16–18 inches away from compassesand sensors!

Fig. 9-9. Typical “bullet-type” electrical connectors. Theseare useful if installed as opposites on the positive and nega-tive return wires in preventing a reverse-polarity situationthat can damage sensitive electronic equipment.

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CD Player

Left Speaker Right Speaker

Fig. 9-10. Basic wiring diagram for a new CD player.

1. Use the cutout template supplied with theplayer and speakers to cut out your mount-ing holes.

2. Install your speakers and the player in theholes.

3. Route all wiring from power sources, groundconnections, and any speaker or antennaleads. Be sure to secure the wiring and pro-vide chafe protection where needed, as de-scribed in chapter 4.

4. Connect all wires to the back of the player andto the speakers, carefully following the printedinstructions supplied with the equipment asto which wire goes where.

5. Test the operation of the equipment. In otherwords, turn it on and see if it works.

6. Finish mounting the equipment chassis in themounting hole. Enjoy!

Figure 9-10 provides a wiring diagram for this in-stallation that includes the speaker wiring.

If you keep the points mentioned here in mindfor all of your DC circuit additions and carefully fol-low the steps outlined, including the tables and chartsin chapter 4, you should have no problem addingyour own equipment to your boat in a safe and pro-fessional manner.

Engine Instrumentation Problems and Solutions

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Chapter 10

Often taken for granted, many times ignored; onmany boats, that’s the general lot of the vast arrayof expensive and delicate engine and navigation in-struments. The truth is that all your instrumentsshould be taken quite seriously and considered animportant part of the safety equipment on boardyour boat. If your engine suddenly stops running20 miles from shore, you could be in serious dan-ger. That incoming thunderstorm could catch youin gale-force winds, or a strong current could pushyou into shoal water before you have time to setan anchor.

It is very important to monitor your instru-ments constantly, because they may provide theearly warning you need to avoid this sort of emer-gency. Your instruments are also the primary com-munication channel between you and your engine,and they will keep you informed about just what isgoing on inside that very expensive and importantpiece of mechanical apparatus.

Understanding what the instruments are tryingto tell you is also important. It doesn’t do muchgood to look at instruments if you don’t knowwhat all those dials and numbers mean. For the be-ginner, misinterpretation of instrument readingscan lead to a lot of false worries. For example, ondual-helm boats, different instrument readings fortemperature, oil pressure, and rpm are not at alluncommon between helm stations. The same istrue with the instruments on twin-engine boats:duplicate instruments for each engine often giveconflicting readings. This is normal and no prob-lem once you understand what is going on.

Mechanical GaugesMany older boats use mechanical gauges, and muchof the information provided in this chapter on elec-trical troubleshooting will not apply to these instru-ments. It’s a good idea to determine what kind of

gauge you have before a problem does crop up soyou’ll have some insight into what the best plan ofaction may be. Look at the back of the instrument.If it has nothing but wires connected to terminals,it’s an electrical instrument. However, if you see anykind of non-electrical tube or cable in addition toone or two wires, you probably have mechanicalgauges. (The wires are for the instrument lights.)Many boats have a combination of mechanical andelectrical gauges.

Most small to medium production boats builttoday use only electrical gauges, mostly because theyare a lot cheaper and easier to install than mechani-cal ones. Since this book is intended for outboardsand smaller powerboats generally powered by IOdrives or gas inboards, I’ll focus on problems withthe electrical instruments on these boats and leavethe mechanical gauges alone.

Common InstrumentInterpretation ProblemsThere are several things to think about when you’reviewing your boat’s instruments. For example, con-sider the actual accuracy of the instruments. For rea-sons that will be pointed out shortly, the readingsyou get from your instruments could be slightly dif-ferent than what’s really going on in your engine.

The quality of instruments used on boats varieswidely among boatbuilders. In fact, discrepanciesbetween readings on different gauges and the actualreadings at the engine are quite common. What you,as a boatowner, should be looking for as you moni-tor your engine’s vital signs is any change from theestablished norm for your particular engine. Anychange in the reading of a gauge is a surefire indica-tion that something is up, and it could be a problem.

As already mentioned, another common situa-tion on boats with dual helms or dual engines (orboth) is a variation in instrument readings between


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stations or between engines. Often, one gauge set willread differently from another—not by much, but dif-ferent nonetheless. The obvious question is, is this aproblem? The answer is no. I have wasted hours try-ing to match gauge readings on boats with duplicateinstruments. Unless I was very lucky or was workingon exceptionally high-quality instruments, my re-sults were less than satisfactory. The best gauges havecalibration screws that enable you to fine-tune theactual readings, but don’t count on finding these ex-pensive gauges on a typical production powerboat.

Some manufacturers (VDO and MerCruiser, forexample) offer sending units designed for twogauges for use on dual-helm boats. Any discrepancybetween the two gauges working on a commonsending unit is caused by voltage drop, the phenom-enon mentioned throughout this book. Since youhave read this far, you know that due to the in-creased resistance to electrical flow in a long wire,the length of a wire has a direct effect on voltagedrop. Well, this extra resistance directly affects theinstrument reading at your console, because mostinstruments rely on variable resistance created byan engine-mounted sensor to give you readings.

Differences in the lengths of connecting wires oninstruments at upper and lower stations, combinedwith manufacturing tolerances in gauges and sensors,ultimately control the actual reading you get at yourinstruments. Don’t panic if you see slight variationsfrom one gauge to another. This is a normal condi-tion, and repeated trips to your mechanic or boatdealer to solve the problem will almost always provefutile. Remember to look for relative changes in yournormal instrument readings; that’s what’s important.

Abnormal Instrument ReadingsAt some point your instruments will indicate that acondition other than the norm exists. It might behigh engine temperature, low oil pressure, erraticrpm, or dozens of other deviations from your normalreadings. Often when there is a change in one instru-ment there is a corresponding change in others.Falling oil pressure might be accompanied by risingengine temperature and falling rpm, for example.

When this occurs, you must respond quickly andverify that a problem does in fact exist. Ask yourself:Is there really a problem, or is the gauge just actingup? Initially, you must assume that a problem doesexist and immediately shut down your engine untilyou can verify that it’s OK.

Verification of engine condition requires somemechanical expertise on your part, and if you’re indoubt, you may need to consult an experienced me-chanic. This works fine at the marina, but offshore itwon’t be possible to call a mechanic, so some basictips are in order. If your boat has an outboard engine,my book Outboard Engines: Maintenance, Trouble-shooting, and Repair will surely help you solve mostcommon problems. If yours has an IO or inboard en-gine, the following steps should point you in the rightdirection.

Low Oil PressureWhen your oil-pressure gauge gives you a low-oil-pressure reading, immediately shut down the engineand check the engine oil level. Refer to your owner’smanual to determine the correct level, if you don’t al-ready know it. While you’re at it, look for any signs ofleaking oil.

If the oil level is correct, an oil-pressure problemis quite unlikely unless your engine has many hourson it (over 1,000 hours for gas engines and evenmore for diesels). Excess engine noise, such as tick-ing sounds coming from the top of the engine block,is a sure indication that a problem exists, and youmay not be able to get the boat home without assis-tance. If in doubt, radio for help; the chance of caus-ing extreme engine damage here is great and notworth the risk.

High Engine TemperatureIf excessively high engine temperature is indicated byyour temperature gauge and the rise occurred sud-denly, you should back off the throttle to an idle andsee if the temperature reading begins to drop. Oftenit will, and it’s preferable to let the temperature stabi-lize before shutting off the engine to scope out theproblem. Suddenly shutting down an overheated en-gine can cause extreme shock to the engine’s pistons,

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inducing the engine to seize. Once the engine has hada chance to catch its breath and stabilize somewhat,shut it off and let it cool down enough so you cancheck the level of cooling water if you have a fresh-water-cooled engine. Next check for a broken fan belton the water pump. If the belt is in order, the mostlikely cause for overheating is a blocked water intaketo the engine’s cooling system.

Follow the steps outlined in your workshop man-ual to determine if adequate cooling water is enter-ing the system. Often the problem is a piece of debristhat’s drawn to the intake port by the suction of thewater pump. In many cases, stopping the boat andbacking down for 10 or 20 feet will dislodge the for-eign object, and all will be well. In any event, youshould spend some time reviewing your engineworkshop manual, getting familiar with the coolingsystem and troubleshooting procedures before prob-lems develop. Carry spare water-pump impellersand fan belts at all times.

Low Voltage ReadingIf your volt gauge suddenly shows a lower-than-normal or a higher-than-normal voltage reading,you can easily verify the accuracy of the gauge bydoing an open-circuit voltage test at your battery.Use your multimeter and take the reading with theengine running as outlined in chapter 5.

Low or High RPMIrregular engine rpm usually shows up as an erraticreading or no reading at all on the tachometer. Ifthe engine is running normally in spite of the erraticreading, get the boat back to shore and follow theelectrical troubleshooting steps outlined in the nextsection of this chapter.

Trim-Gauge ProblemsOf all the instruments on a boat with an inboard/outboard engine, the trim gauge is the one with thehighest failure rate. This is because the sending unitson these boats are often located underwater on theside of the engine drive unit. Here they are exposedto the worst environment any electrical equipmentcan experience.

Faulty trim-gauge readings always indicate anelectrical malfunction and have nothing to do withthe function of the drive itself. To be safe, take a lookover the transom just to be sure the drive is downbefore starting the engine.

On inboard engines, hydraulic trim tabs oper-ated by an electric servomotor control trim. Theyhave a comparatively low failure rate, because all theelectrical components are located inside the hull andare not exposed to seawater.

Fuel Gauge ProblemsCommon sense should assist you with any erraticreading on your fuel gauges. As soon as you buy anew boat, you should establish an approximate fuel-consumption rate. Calculate the gallons of fuel usedby your engine per hour of running time at differentrpms. Based on that usage and the capacity of yourfuel tank, you should be able to estimate the amountof fuel in your tank and use that estimate to judge theaccuracy of your fuel gauge. For example, if you burn10 gallons per hour at 3,000 rpm and have a 50-gallon fuel tank, you can safely operate your boat forfour hours and still have an emergency reserve, nomatter what your fuel gauge tries to tell you.

Problems with fuel gauges, like problems withtrim gauges, are almost always the fault of the tanksending unit. The test procedure for this will befound later in this chapter.

General Instrument TroubleshootingThe pros say that whenever an instrument problemcrops up, you should always verify that a problemdoes in fact exist by swapping the engine gauge with aquality shop gauge, which is often a mechanical gauge.This is good advice, but unless you have a personalfriend who’s a mechanic (which is a great idea), youprobably won’t have ready access to a set of qualityshop gauges. The tips that follow will help you aroundthis deficit and to successfully solve most instrumentproblems. Remember, if you still have doubts aboutyour abilities to attack your instrument problems afterreading the steps outlined here, your best bet is to callin a pro who has the equipment to do the job properly.

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Troubleshooting the TachometerTachometer circuits come in several types, depend-ing on the engine used in your boat. The primarydifferences are between those used on gasoline andon diesel engines. Modern diesel tachometers aregenerally connected to the back of the engine alter-nator at a terminal labeled “tach.” This terminalsenses the AC pulses inside the alternator and sendsthem to the tachometer where the pulses are trans-lated into engine rpm.

The tachometer on most gasoline engines gets itssignal from various points in the ignition system. Theonly way to be really sure where your tachometer isgetting this signal from is to use your wiring diagramand service manual. On gasoline engines, the sens-ing wire is usually gray.

If there is any break in this wire between the ig-nition circuit and the back of the gauge, the tach-ometer will not give a reading. Any short circuit inthis wire can short out the ignition system and causethe engine to quit.

Figure 10-1 shows a typical diagram for a tachom-eter circuit on a gasoline engine. In addition to the

gray sender wire, wires provide battery power to theinstrument and a return to ground. Figure 10-2 shows the battery power to the tachometer be-ing checked with the ignition key on. Where theABYC color-coding is used, this wire will be purple.Note that a small jumper is built into the gauge toconnect power to the instrument light.

If no power is available at this wire when the igni-tion key is on, make sure that the lanyard safety keyis installed, if the boat has one (all newer boats haveone). If it is, using the methods previously described,check all the connections and the condition of thelanyard switch. Continuity tests and voltage tests maybe used here.

Next, verify the continuity of the ground withyour multimeter. Check between the “GND” (blackwire) terminal on the back of the tachometer and agood ground on the back of the instrument panel, asshown in figure 10-3 on page 151.

To Pick-Up Pointof Ignition

FromIgnition12V

InstrumentCommonGround

L

+12V

G

PUL

Fig. 10-2. Testing battery power to the tachometer. This testis to determine if the instrument is getting voltage to run.My red meter lead is connected to the gauge terminalmarked “IGN,” which will usually have a purple wire at-tached. My multimeter’s black lead is connected to a com-mon “GND” terminal on the gauge. These will almostuniversally have black insulated wire connected to them.Fig. 10-1. Wiring diagram of a typical tachometer circuit.

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If you find continuity in theground wire, good ground for thegauge exists, and the powering cir-cuitry for the instrument is in good order. Next, use your engine wiringdiagram to determine where thetachometer gray wire connects to yourignition system. With the ignition keyoff, determine if you have continuitybetween the connection point on theback of the tachometer and the pointon the engine where it terminates(usually at the ignition module). Ifcontinuity exists here, and the powerand ground circuits are functioningnormally, the only remaining possibil-ity is that there is a problem in thegauge itself, and a new unit should beinstalled. (Note: One slight possibilityis that the tachometer is not getting asignal from the ignition system via thegray wire from the ignition system it-self, but this is extremely rare and al-most always associated with anignition-system problem as well.)

If you need a new tachometer,make sure to follow any calibration instructions provided with the gauge.Manufacturers generally provide onegauge for four-, six-, and eight-cylinderengines. The correct number of cylin-ders should be set using a small cali-bration screw on the back of the gaugeas shown in figure 10-4. Select the set-ting that corresponds with the numberof cylinders on your engine.

If you have a diesel or gasoline en-gine that uses the previously mentioned“tach” sensor at the alternator, you stillneed to verify that the tachometer isgetting 12 volts with the key on and thatit’s connected to a good ground.

If you find that everything I havementioned so far is in order and yourtachometer is still not reading, theproblem may be an open circuit in the

Fig. 10-3. Verifying instrument ground continuity at the tachometer. As withall boat circuits, the power feed is only as good as the ground return. Here I’mchecking for a good ground for the instrument. My meter leads are connectedto the “GND” terminal on the tachometer and to a common ground stud onthe back of an adjacent instrument. Since we’re checking for continuity, it re-ally doesn’t matter which lead goes where.

Fig. 10-4. Tachometer calibration. The circular scale on the back of thetachometer shown here is used to select the appropriate calibration for yourengine. This is most often done with a mini-slotted screwdriver and turningthe setting screw inside the instrument to the appropriate point on the dial.

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sensor wire from the alternator to the tachometer ora fault within the alternator itself. Since this sensorwire is sensing voltage from within the alternator,no signal here means no voltage inside the alternator.The basic checks of the charging system described inchapter 6 will help isolate the reason that yourtachometer quit.

One caution here, however: On many diesel en-gines, a separate oil-pressure sender on the engineswitches the field voltage (see chapter 6). This way,even if the ignition key is left on, the alternator willnot get excitation voltage to the field windings untilthe engine is actually running and oil pressure closesthe circuit. These senders have a high failure rate andare often the cause of alternator failure on a diesel.

Check the engine manual to see if you have oneof these switches. If you do, in order to check forfield voltage at the “F” terminal on the back of thealternator, either bypass the oil-pressure switchwith a jumper wire or do the voltage test with theengine actually running.

If no voltage is found, then the switch on the en-gine is not getting voltage from the ignition switchor the oil-pressure switch is defective. To check, fol-low the procedures outlined throughout this bookfor testing any switch. If voltage is getting to the al-ternator, and all the other procedures from chapter6 for testing the alternator have been followed, aproblem with the alternator or the internal voltageregulator is indicated. Remove the alternator andsend it out for overhaul.

Once you have determined that the alternator isnot the cause for your tachometer failure, verify thecontinuity of the wire connecting the tachometer tothe back of the alternator. Disconnect the wire atboth ends (at the tachometer and at the back of thealternator) and use your multimeter. If you find con-tinuity, the problem is within the tachometer itself. Ifyou don’t, there is a break in the wire that should belocated and repaired.

Voltmeter ChecksIn recent years, console-mounted voltmeters have re-placed or (on expensive instrument panels) supple-mented ammeters as indicators of battery conditionand state of charge. This change has taken place for

economic reasons more than anything else. Volt-meters are less expensive than ammeters, and theyare much cheaper to install. Ammeters require heavywires or expensive shunts (see chapter 3), whereasvoltmeters for the largest batteries can be installedusing 16 AWG wire. Voltmeters impart slightly dif-ferent information than ammeters, but they are avery useful way of keeping an eye on your battery. Adigital voltmeter coupled with an electronic batterycharger, or smart charger, is an excellent way of mon-itoring the charge cycles discussed in chapter 6.

If your voltmeter quits reading, simply use yourmultimeter to verify that battery voltage is getting tothe terminal at the back of the instrument and thatthe ground lead is properly attached and connectedto ground. If power feed to the gauge is OK and theground is good, there should be no questions here;the gauge is bad and needs replacement. A gaugereading higher than normal indicates a charging-sys-tem problem—probably with your voltage regulator.To solve this problem, follow the procedures out-lined in chapter 6.

Figure 10-5 on page 153 shows the voltage andground verification checks being made at the backof a typical voltmeter.

Temperature, Fuel, and Oil-Pressure GaugesEngine service manuals generally combine these en-gine instruments into one group for diagnostic pur-poses, because they all operate on the same basicprinciple: they all use a variable resistance to groundto generate the instrument reading. Figure 10-6 onpage 153 shows a simplified wiring diagram that il-lustrates how these gauges work.

Temperature GaugesLike all other gauges (except the mechanical ones),the temperature gauge needs battery power and agood ground to function. If the gauge stops func-tioning, a simple way to verify that the electrical cir-cuits are in order is to disconnect the wire at thesending unit (the variable resistor on the engine) andshort the wire to ground with your ignition switchon. If the needle moves all the way to the right (tomaximum temperature), the problem with the cir-cuit is a faulty sending unit, which should be re-

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placed. If there is no change in the position of theneedle, trace the power to the instrument and verifythe continuity of the ground lead. Replace or repairthese wires as needed.

If both of these leads are in good order and be-having as they should, the fault is in the instrumentitself. Figure 10-7 shows the wire disconnected at the sending unit and shorted to the engine block.This is what your dash-panel-mounted instrumentshould read if the fault is simply with the sendingunit, which is the most common difficulty. This testis for a one-wire sending unit. If your unit has twowires attached to it, disconnect one of the wires fromthe sender and touch it to the terminal on the senderfor the other wire. Watch the gauge with the ignitionon, or get someone to watch the gauge needle foryou. If the needle moves as you connect these leads,the problem is in the sending unit.

Fuel GaugesFuel gauges are wired exactly as temperature gaugesbut use a different type of variable resistor as thesending unit. The senders are located inside the fueltank; you need access to the top of the tank to locatethe senders and the wiring. To test the sender, turnthe ignition key on, disconnect the wire from thesender, and ground it at either the black lead on thesender or directly to the tank. Observe the gauge.

Engine or TankSending Unit

Ignition 12V

LT

+12 GND

SEND

InstrumentCommonGround

Fig. 10-5. Verifying voltage and good ground at the volt-meter.

Fig. 10-6. Simplified wiring diagram for temperature, fuel,and oil-pressure gauges.

Fig. 10-7. Testing the temperature sending unit. With thewire to the sender removed, I’m grounding it out on the en-gine block with the ignition key in the “on” position; theneedle on the temperature gauge on the dash panel shouldread at the maximum side of the gauge.

154


Senders on metal tanks often have only one wire,and the sender grounds to the tank itself. Discon-nect the wire and ground it on the tank. In eithercase, if the needle moves so that the gauge reads full,the sender is bad and must be replaced.

In some instances fuel gauges work fine at somefuel levels and not at others. This erratic reading is afunction of the sender design, and partial failure isnot uncommon. To check, remove the screws hold-ing the sender in place on the top of the tank and liftit out. Next, attach a jumper lead between the tankground lead and the grounding connection on thesender. Again, with the ignition key on, move thefloat on the sender up and down while carefully ob-serving the gauge on your instrument console. Youmay need an extra set of eyes to help you here, de-pending on the distance between the sender and thegauge. If the needle on the gauge acts erratically asyou move the float assembly up and down, the floatsender needs replacement.

Figure 10-8 shows a sender removed and beingtested. An important safety note here is to carefullyinspect the condition of the gasket sealing the floatmechanism to the tank. If any doubt exists as to itscondition, replace the gasket. A fuel leak here is ex-tremely dangerous and cause for immediate concern.

If your tests of the fuel-gauge sending unit causeno movement of the needle on the gauge, verify thatyou have power and good ground at the instrument,just as with the temperature gauge already described.If this fails to locate the problem, replace the gauge.

Oil-Pressure GaugesOil-pressure gauges are tested in the exact same way asboth the temperature and fuel gauges mentioned al-ready. Figure 10-9 on page 155 shows the location of atypical oil-pressure sending unit on a General Motors“V” block used widely by MerCruiser, OMC, VolvoPenta, and other marine-engine manufacturers. Forthe exact location of the sending unit on your engine,refer to your engine workshop manual.

Trim GaugesAs mentioned earlier, trim gauges, generallyfound only on outboard and IO boats, havean extremely high failure rate, because thesending units on these boats are located un-derwater on the engine drive unit.

These sending units are sealed and use twowires to connect the sender to the inside ofthe boat. The wires are fed through the driveunit’s gimbaled bracket assembly, disappear-ing behind the engine where they are ex-tremely difficult to get at. Besides thedifficulty of getting to the wires, the holewhere the wires pass through the transommust be properly sealed to prevent seawaterfrom leaking into the boat. Unless you’re anexperienced technician, I do not recommendattempting to replace these senders on yourown. This is a good job for a professionalwith experience not only in the replacementof trim-gauge sending units but their properadjustment as well.

Finally, if you have any real doubt about theaccuracy of your gauges, you should consult aprofessional with the mechanical and elec-

Fig. 10-8. Fuel tank sender removed and being tested. Move the floatup and down while watching the ohmmeter. Look for a progressivechange in resistance value. Any “OL” readings while performing thistest indicate a “dead” spot in the sender, and it will need replacement.

155


tronic shop gauges necessary to verify exactly what’sgoing on with your engine. Once proper operation hasbeen verified in this manner, record the normal read-ings of your gauges. Remember, while underwayyou’re looking for readings outside these pre-estab-lished norms.

If you follow the steps outlined in this chapter, you’llhave the confidence and ability to tackle and repairmost instrument failures that crop up on your boat.Remember that, as with all the other sections of thisbook, you should never attempt to go too far with yourdiagnosis and repair without the aid of your workshopmanual. Also remember that the basic electrical trou-bleshooting and repair procedures already discussedwill carry you through any diagnosis of instrumentproblems.

The FutureFigures 10-10a and 10-10b show how far we have comesince the first edition of this book. New boats today willlikely be equipped with a networked system for dis-tributing engine data, among other things. The Mer-cury Marine SmartCraft display in figure 10-10a is anintegrated part of that system, and effectively replacesthe traditional gauges discussed in this chapter. Thedata come from an engine-mounted computer like theone shown in figure 10-10b. All wiring is done throughproprietary harnesses with multiple-pin plug assem-blies as in figure 10-10b. Troubleshooting instrumen-tation problems on these systems is a bit more

complicated than some of the procedures described forconventional instruments. But with an ohmmeter, youcan check continuity of the pin connections from oneend of the harness to the other and at least determineif there is a problem with the harness or a plug assem-bly. Beyond that there is not much you can do with-out specialized equipment that goes beyond the scopeof this book. One resource for those that want to learnmore about these systems is my latest book, AdvancedMarine Electrics and Electronics Troubleshooting.

Fig. 10-9. An oil-pressure sending unit on a GM V8 engine.On this engine it’s located next to the ignition distributor.

Fig. 10-10a. SmartCraft display. Fig. 10-10b. Engine-mounted computer.

What Is Alternating Current?Throughout this book on electrical systems forpowerboats, I have been talking about direct-current electricity, simply because more than 90 per-cent of all systems on most boats use DC power. Ofcourse, most of us already know what alternatingcurrent is, but let’s run through it one more timefor review.

Most technically aware boatowners know that ACis the stuff that can kill you, and that DC electronsflow in one direction whereas AC electrons reversedirection. I will discuss AC dangers and safety lateron, but let’s first take a closer look at the second item,this apparent difficulty that AC electrons have inmaking up their minds which way to go. In chapter5, I discussed the manner in which direct-currentelectrons flow through a circuit from the negativepole of a battery (the cathode) to the positive pole(the anode). With alternating current, of course, theanode and the cathode repeatedly and rapidly reversepositions. Instead of flowing in a continuous streamfrom one end of the circuit to the other, the electronsin an AC circuit travel only a short distance beforechanging their minds and rushing back to where theystarted. They do this over and over again, and whilethe electrons in an AC circuit get nowhere, the powerthey generate has some important qualities thatmakes it better than DC for certain chores.

Before I go any further, let’s get some morebasic terminology out of the way.

Basic AC Terminology

� Polarity. Obviously, with the anode and cathode

continuously reversing positions, our old concept

of opposing plus and minus terminals, or poles,

no longer works for AC. Many electricians who

should know better (almost all of us, in fact) refer

to the hot lead (the black one) in an AC circuit as

the positive and the grounded lead (the white

one) as the negative. In actuality, each wire takes

turns being positive, then negative, several thou-

sand times a minute. If you choose to use this pos-

itive/negative distinction to describe AC wires,

you must keep in mind the fact that there is no

true polarity in an AC circuit, as there is in a DC

circuit.

Ironically, because of the physics involved, the

proper wiring of AC circuits (or polarity, if you

like) is even more critical than it is in DC circuits,

as we will discover a little later on.

� Frequency. The frequency of an AC circuit is sim-

ply the rate at which the current reverses itself. In

most American countries the standard is 60 cy-

cles per second, which means that the electrons

hop back and forth 60 times every second. Fre-

quency is measured in Hertz (Hz), so the standard

in the United States is called 60 Hz service. (Eu-

rope and Asia use 50 Hz service.)

On boats, frequency is particularly important

when dealing with generators, as we will see.

� Resistance. Resistance, as you’ll recall, is an im-

portant component of any DC circuit. It’s equally

important with an AC circuit, but it carries the

added influence of induction (the generation of an

electrical current in a wire exposed to a magnetic

field). Induction becomes important with AC be-

cause of the higher voltages (remember how the

strength of a magnetic field increases with an in-

crease in voltage?). Also, the tendency of resistance

in a DC circuit to cause a buildup of heat, which

in turn causes an increase in resistance, is not as

important in an AC circuit; the reversing electrons

just don’t get a chance to generate a lot of heat be-

fore it’s time to turn around and go back to where

they started. This makes AC much more efficient

than DC when higher voltages are needed, and it’s

one of the big reasons we use it at all.

Alternating Current and AC Equipment

156

Chapter 11


� Impedance. Impedance is the combined effect of

resistance and induction. The place you’ll hear the

word used the most around boats is when working

with your radio antennas (see chapter 12).

� Voltage drop. The efficiency of AC is also the rea-

son that voltage drop, which I have repeatedly

stressed as one of the most important considera-

tions in any DC circuit, just isn’t important in an

AC circuit. Also, because of the higher voltages

used in AC, a much lower amperage is needed to

do a given amount of work (remember Ohm’s

law?), which further reduces the importance of re-

sistance and voltage drop.

� Waveform. Most working electricians will have

access to an oscilloscope, a testing device that

shows the track of an electrical impulse as it re-

verses direction through a single cycle in an AC

circuit. The resulting sinusoidal wave shows the

variation in voltage from zero up through the

peak at about plus 170 volts, then back to zero,

then down to a minus 170 volts, then back to zero.

This fluctuation averages out to 120 volts, and is

why I suggested earlier that if you intend to work

with AC electricity even a little, you should invest in

a true RMS (root-mean-square) multimeter. The

cheaper meters (average-responding type) read the

peak voltages without consideration of the time

the circuit is at zero voltage, and are only effec-

tive for measuring true sinusoidal AC wave forms.

When working on boats, waveform is most im-

portant when considering inverters. No, you don’t

have to run out and buy an expensive oscilloscope.

Just knowing what a waveform is and why it’s im-

portant is plenty for now.

AC on Your BoatJust a few years ago, any use of alternating currenton board any small boat (under 35 feet or so) wasextremely unusual. Some of the fancier boats didhave a dedicated battery charger (Constavolt was apopular one), but the best of these were expensiveand inefficient, and the good ones weighed nearly100 pounds. My, how times have changed! Today it

seems that even the smallest of boats is comingthrough with at least a rudimentary AC system.

Boaters now demand onboard systems to run ashore-power-fed battery charger and electric hot wa-ter. In New England, where I live, small boats mighthave an electric space heater in the cabin. Even 23-to 27-foot-long walk-around fishing boats andweekenders, on which designers wouldn’t havedreamed of installing an AC system just 10 years ago,now have several outlets in the cabin as standardequipment.

Boaters are demanding more of the comforts ofhome, and builders are doing everything they canto oblige the craving for luxury. With all of this in-crease in AC equipment on boats comes the need tohave a basic understanding of how alternating cur-rent works and how it gets integrated into yourboat’s total electrical system. AC power will comeon board your boat from one of three sources: a di-rect plug to shore, an AC generator, or a DC-to-ACinverter. Since both the AC and DC systems are runclosely together throughout your boat, you needto make sure you know which system you’re work-ing with and how to identify the key components ofeach system. Never forget that alternating currentcan kill you!

AC SafetyAlternating current can be extremely dangerous if it’snot handled with care and common sense. The haz-ard of a lethal electrical shock is real and present anytime you have AC on your boat, and a poor-qualityAC installation is as much of a fire hazard as a badDC installation. Happily, the basic rules for handlingalternating current on your boat are clear, and thesesystems rarely cause a problem if these simple rulesare followed.

Nearly all accidents involving AC on boats arecaused by ignorance, laziness, blatant stupidity, orsome combination of all three of these things. Mostoften a boatowner attempts to cut corners to save alittle time or a few dollars on an installation, and getshurt or damages the boat in the process. On oneboat I recall, the owner thought the best approach to

157


158


AC upgrades was to hire a licensed electrician to in-stall the AC service. The problem was that this par-ticular electrician, although probably a competentworker on shore-based systems, had no experiencewith marine electrical installations. Within monthsafter a major refit to the boat, a fire broke out onboard, and the boat burned to the waterline. The in-surance investigation revealed that the fire wascaused by the boat’s new AC shore-power system.This was a lesson hard-learned for the owner, andfor the electrician!

If you’re having an AC system professionally in-stalled on your boat, ask your electrician if he or shehas been certified by the ABYC to work on boats. Ifnot, you might want to wait until they get certified, orsimply look around for an electrician who has passedthe ABYC certification program. Quality marineelectricians are proud of this certification, and will al-ways promote the fact that they are certified, so itshouldn’t be too hard to locate one in your area.

Basic AC Safety RulesI could easily fill up two or three pages with safetyrules that all of us should observe when working withAC, but most of these rules are common sense. A caserecently came to my attention where an electricianwho had forgotten his wire stripper was removing in-sulation with his teeth. Everything went fine until hetried to strip the hot (black) wire while holding onto the bare end of the grounded (white) wire. Hewoke up in the hospital with a good part of his lipsburned away. Therefore, one rule might be: Alwaysturn off the power before you strip wire with yourteeth. Another, older case suggests another rule:Never change a light bulb while standing in a bathtubfull of water. There are lots more, but I have coveredthem all with rule number 10 below. Here are a fewothers that apply specifically to boats.

1. Use only marine-grade products, wiring, terminalstrips, and connectors on your boat.

2. Observe polarity at all times. The orientation ofthe hot wire (also referred to as the ungroundedconductor) and the ground wire (the groundedconductor) and color-code matches are all veryimportant. Reverse polarity can at the least cause

certain equipment not to function, and at worst,it can destroy expensive gear.

3. When working on the AC system, disconnect thepower at all times except when testing for voltageand amperage at points throughout the circuit.

4. Never work on a system with wet hands or feetor when any of the components are wet.

5. Make sure the boat is connected to a proper andtested ground, even when working with thepower off. This means that whenever possible,you must avoid working on AC when the boat isat anchor or on a mooring.

6. Always wear rubber-soled shoes (deck shoes andrunning shoes are fine) when working on ACpower. It’s also an excellent idea to wear rubberknee pads, because most of your work on a boatwill be done while kneeling.

7. Never work on AC service with distractions suchas a television or chatty friends present.

8. Ground-fault circuit interrupters (GFCIs) shouldbe tested at least monthly to ensure proper func-tion.

9. The common practice of clipping off the thirdprong (the grounding prong) of a three-prongedplug creates a real shock hazard on board a boat,and this should never be allowed. Any cords orequipment you have where this all-important ter-minal has been removed should have that thirdterminal replaced.

10. Avoid doing obviously dumb things (such asstanding in water or putting hot wires in yourmouth) when working with AC.

Let’s take a more detailed look at specific systemlayout and the key standards as established by ourfriends at the ABYC.

Color Coding for AC WiringUnlike the DC systems already discussed, we willonly be working with three colors for simple, small-boat AC wiring schemes. Larger boats using com-bined 120/240-volt systems use several additionalcolors for the extra legs of the circuitry that combine

159


to make the higher voltage, but these systems areused only on larger yachts, and a discussion of themwould go beyond the scope of this book. I’ll focuson only the most common, single-phase 120-volt,20- and 30-amp systems here.

The three colors used with AC in the UnitedStates are black, white, and green. The black conduc-tor is used only for the AC ungrounded (positive)lead. Some people refer to this as the hot lead. Thisexplains the trend toward using yellow as a DC neg-ative conductor in accordance with the ABYC’s rec-ommendations for DC systems. There is an obviousrisk of confusing the hot AC positive wire with therelatively inert DC negative wire, which has tradi-tionally been black. Increasingly, new-boat buildersare moving to the yellow DC negative wire as a meansof more clearly separating the AC service from theDC service. Manufacturers are now making the yel-low insulated wire available in all gauges includingbattery-cable sizes.

With AC, the white lead should always be the neg-ative, grounded lead, and green should be the ground-ing lead, which offers shock protection to the boat-owner. This green wire, which does not normallycarry current, is one of the most important keys topreventing the “zap” you could receive from electri-cal appliances on board if they are not properly con-nected or if a fault occurs anywhere in the system.This, coupled with the fact that appliances will workjust fine whether this wire is attached or not, is whyensuring continuity throughout the circuit all theway to the shore-power box is crucial.

ISO Color CodingIf your boat is not built to U.S. specifications, theremay be some variations in the color-coding schemedescribed above. The International Standards Orga-nization (ISO), whose standards are used in manycountries, prescribes the following colors for use withAC installations:

� For hot conductors (ungrounded), either black or

brown wires must be used.

� For neutral (grounded) conductors, either white or

light blue wires must be used.

� For ground (grounding) conductors, either green

(as with the U.S. system) or green with a yellow

stripe may be used.

If your boat is wired using the ISO system andyou’re making additions or modifications, it’s an ex-cellent idea to stick with the existing color code ratherthan changing or mixing the codes. However, in theUnited States you might have trouble finding wire inISO colors, in which case you should improvise yourown coding system as described in chapter 2.

Reverse PolarityReversal of the black and white leads on an AC cir-cuit creates reverse polarity, where the white wirebecomes the hot lead and the black wire becomesthe grounded lead. This condition can destroy po-larity-sensitive equipment, such as motors, TVs,and microwave ovens, and it creates a seriousshock hazard.

The bottom line here? You need to be certain thatwiring color coding is matched and appropriately con-nected through every inch of the AC circuit, from theshore-power source all the way through your boat.

Testing for PolarityMany newer boats with AC distribution panels havea polarity-test button right on the panel. If you don’thave one of these panels, you can check polarity withyour multimeter every time you plug in, or you canbuy a simple and cheap circuit tester (see figure 11-9on page 167) that plugs into any standard outlet. Ifthe indicator lights on the tester don’t light up in theproper sequence, you know you have reverse polaritysomewhere in the circuit, and you must shut downthe circuit until you find it and fix it.

Figure 11-1 on page 160 illustrates typical ACwiring connections from the shore-power inlet onyour boat through the AC panel to a standard outlet.

Comparisons between AC and DC CircuitsAs with the DC circuits discussed throughout thisbook, things like amperage and voltage are major

160


considerations when wiring for AC. Unlike DC,however, voltage drop through the circuit is reallynot much of a factor in AC circuits. It’s not that volt-age isn’t lost as it finds its way through an AC circuit, but for the lengths of wire runs used on the small boats discussed here and because of thephysical considerations cited above, voltage drop isan insignificant factor—so insignificant that theABYC doesn’t even take it into consideration in itselectrical standards for AC circuits. Wire sizing of ACcircuits is easier as a result of this disregard for volt-age drop, with amperage requirements being the onlyconsideration when designing circuits.

Wattage, however, is an additional element wemust take into account here. In chapter 1, you’ll re-call, I discussed the Ohm’s law equation and an addi-tional variation for watts, the unit of electrical power.If needed, go back and refresh your memory on thisprocess, because the wattage equation really has somepractical use when dealing with AC.

In the United States, as a requirement of the Un-

derwriters Laboratory (UL) rating of AC equipment,each electrical device must be marked with either theoperating voltage and amperage, or the operatingvoltage and wattage. Typically wattage is given.Knowing this, you can easily find out the amperageof a given appliance by dividing wattage by the oper-ating voltage.

This vital information is step one in the determi-nation of overcurrent protection ratings as well aswire sizing. No adjustment, or de-rating, of the ampacity of the conductor for length of wire run isnecessary as it is with DC circuitry.

With AC, a different criterion comes into play.Heat generated by whatever electrical resistance ispresent will require de-rating the wire gauge.Bundling of AC conductors requires that wire sizesbe increased. Also, as with DC, wires routed throughengine rooms must be larger than those used out-side the engine room, to deal with the higher tem-peratures.

Figure 11-2 shows what a typical bundle of AC ca-

Und

ergr

ound

Con

duct

or (B

lack

)

ShoreConnection

Gro

unde

d N

eutra

l Con

duct

or (W

hite

)G

roun

ding

Con

duct

or (G

reen

)

Blac

k

Shore Power Cable Connector

Shore PowerCable

Power Inlet (Electrically insulated from the boat if isolator is installed)

2 Pole, 3 WireGrounding

Type Plugs & Receptacles

Shor

e Si

deBo

at s

ide

OptionalGalvanicIsolator

PolarityIndicator

To Engine NegativeTerminal or its Bus

Main Shore PowerDisconnect

Circuit Breaker

Whi

teG

reen

Branch CircuitBreaker (Typical)

120 VAC Device

120 VAC GroundingType Receptacle

Fig. 11-1. Typical shore-power wiring diagram through the AC distribution panel to an outlet. (© ABYC)

161


bles would look like in your boat. Figure 11-3 is atable from the ABYC’s section E-11 showing the am-pacity of a typical length of triplex AC boat cable.

Remember that the green conductor does notnormally carry current and is therefore excludedfrom the process.

Another common question that comes up has todo with routing AC and DC wiring in the same bun-dle. Although the ABYC allows this practice as longas the wiring in question is separated by an appropri-ate sheath, which can be the outside skin of a typicallength of AC boat cable, it’s much better to keep ACand DC wires in separate bundles. The possibility ofcross-induction (remember, any wire with current

Wire tie

Fig. 11-2. An AC wiring bundle.

Fig. 11-3. ABYC ampacity table for a single run of triplex. (© ABYC)

TABLE VIII-A-ALLOWABLE AMPERAGE OF CONDUCTORS WHEN NO MORETHAN 2 CURRENT CARRYING CONDUCTORS ARE BUNDLED

162


flowing through it generates a magnetic field) is realand may cause problems with sensitive electronicequipment, as we’ll see in the next chapter.

Marine versus Residential MaterialsMany boatowners who want to add AC service toboats that came with only a simple DC setup as stan-dard equipment, head for the nearest residential elec-trical supply house to get the gear for their new circuit.Some people have undoubtedly seen boats that cameright from the factory with this residential gear in-stalled; Square-D switch boxes, panels, and breakers,as well as the solid-copper wire known as Romex, havebeen used in original-equipment installations by vari-ous boatbuilders over the years. Virtually none of thishousehold gear meets current ABYC standards, andit’s definitely not recommended that household ACgear be used on board your boat. In fact, if your boathas household-rated AC equipment, one of your firstorders of business should be to remove it and replaceit with appropriate marine gear. Remember what hap-pened to the boat and licensed electrician mentionedearlier? You could be next!

Some appropriate exceptions to this rule on marine-grade versus household material are thecommonly available plastic outlet boxes, face plates,and plug assemblies that all work just fine on boats aslong as they are the all-plastic type. Even with these,however, it’s best to throw away the steel screws thatusually come with the equipment and substitutestainless or brass screws instead.

Wire for ACMost 120-volt AC circuitry on small powerboats willuse 12-gauge, tinned triplex boat cable for the en-tire wiring scheme, regardless of the length of therun or the anticipated load. You can, of course,legally and safely use 14-gauge wire for your AC cir-cuits (as many builders of budget boats do), butsince the savings amount to about $30 for a 100-footroll, you might as well go ahead and use the heavierand slightly safer wire. Tinned triplex with AC color-coding (black, white, and green) is available fromWest Marine and most other chandlers.

I’ve said it before, and I’ll say it again: Don’t use

Romex or any other solid-copper wire on your boat.If you have any already installed, replace it withproper boat cable.

As for the insulation temperature rating of ACwiring, rated boat cable from a marine supply storewill probably have a 105°C rating, although there isstill some 90° cable available, and many boats alreadywired have this lower-rated wire in use.

Figure 11-4 on page 163 shows the ampacity for a group of two to three of these triplex cablesbundled together. The higher ratings in the tablesare specialty cables not readily available, and thelower ratings are not commonly available either. Forany new work you’re doing, the 105° cable is morethan adequate for typical small-boat installations.

AC Overcurrent ProtectionAs for rating and location in circuits of overcurrent-protection devices (fuses and circuit breakers), thesame basic rules apply for AC circuits as for DC cir-cuits. An exception is the rating and location ofbreakers for feeder wires from the shore-power inleton your boat to your main AC distribution panel.Refer back to chapter 4 to refresh your memory re-garding the 7–40–72 inch location rule and the100–150 percent rule. The ABYC allows a run of upto 10 feet between the shore-power inlet and themain circuit breaker on the main feed conductors toyour boat’s AC distribution panel. On boats of thesize for which this book is intended (up to about 35feet), this will usually mean the main breaker will belocated on the AC distribution panel itself. For largerinstallations where the distance between the inlet onthe boat and the panel exceeds 10 feet, a circuitbreaker is required on the feed wire before it reachesthe panel. These breakers must be of the trip-free va-riety, just like those used for DC, so they can’t be heldclosed by the operator. This means you must use onlymarine-rated circuit breakers for any replacements toexisting services as well as for any new circuits.

AC Circuit-Breaker TypesCircuit breakers for use with AC systems must be ofthe trip-free variety, as already stated. But an addi-

163


tional consideration is whether or not they need to beof the single- or double-pole configuration. Almostall circuit breakers used with DC systems are single-pole breakers with two terminals on the back de-signed to be connected in series with the DC positivefeed wire. A notable exception is with some DC panelmaster breakers where two single-pole breakers willbe ganged together.

For all AC circuits, the main circuit breaker mustbe of the double-pole type. With this type, the breakerwill have four terminals and be designed to simulta-neously trip both the black AC positive conductorand the white AC negative conductor. This addedsafety measure provides protection even with reversepolarity. So in effect, even if the wiring entering the

boat from the dock is set up incorrectly, the breakerwill still do its job.

If your boat’s AC distribution panel is equippedwith a reverse-polarity indicator, you may use single-pole breakers for any branch circuits on the panel ordownstream from the panel. If you’re buying a newdistribution panel to add AC to your boat, be sure toget one equipped with this reverse-polarity indicator.Any money saved on the panel by not getting this fea-ture will be false economy in the long run—the inci-dence of reverse polarity at marina shore-power boxesis just too high! Figure 11-5 on page 164 shows botha single- and double-pole breaker of the approvedtype. Figures 11-6a and 11-6b illustrate how these twotypes of circuit breakers are wired into an AC circuit.

Fig. 11-4. ABYC ampacity table for a bundled run of up to three triplex cables. (© ABYC)

TABLE VIII-C-ALLOWABLE AMPERAGE OF CONDUCTORS WHEN 4 TO 6 CURRENT CARRYING CONDUCTORS ARE BUNDLED

164


Basic AC Outlet ConnectionsWhen installing a new AC outlet, the black wire tothe back of the outlet must be connected to the copper- or brass-colored screw terminal. The whitewire must be connected to the white or silver termi-nal, and the green wire must be connected to thegreen terminal. You must use the captive-crimp ter-minals described in chapter 4 for all connections tothe outlet. The spring-loaded press-on terminalsused for some residential outlets are for use withRomex solid-copper wire and are never appropriatefor the stranded wire you must be using if you’re

adding an outlet. The screw-terminal variety ofhousehold outlet is just fine as long as a proper ring-eye, or captive terminal as described in chapter 4, iscrimped to each wire. This connection scheme mustbe followed throughout the entire boat. It’s easy tomess up here and have the outlet still work, but youcould possibly have introduced reverse polarity tothat outlet that will not be detected by your ACpanel-mounted reverse-polarity indicator.

On a boat, all AC connections must be enclosedin a protective box. I’ve seen outlets installed onbulkheads with the back side of the outlet exposedto the inside of a cabinet or hanging locker. Onemetal coat hanger or soup pot sliding into the back ofthe outlet, into contact with the terminals, is all itwould take to create an instant short circuit. Thereadily available and quite inexpensive plastic outletboxes used in residential wiring are perfect for thispurpose. They’ll last forever, they can be easily in-stalled from the back of the assembly (sometimeswithout even removing the outlet), and they preventany short circuits or shock hazard.

Figures 11-7a and 11-7b show a typical three-pronged outlet and indicate which color conductorshould be servicing each prong.

Und

ergr

ound

Con

duct

or (B

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)

ShoreConnection

Gro

unde

d N

eutra

l Con

duct

or (W

hite

)G

roun

ding

Con

duct

or (G

reen

)

Blac

k


Shore PowerCable




Shor

e Si

deBo

at s

ide




Circuit Breaker

Whi

teG

reen


Fig. 11-5. Single- and double-pole AC circuit breakers.

Fig. 11-6a. Wiring diagram of a double-pole breaker (circled area) that will simultaneously trip and open the black andwhite conductors. (© ABYC)

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Und

ergr

ound

Con

duct

or (B

lack

)Shore

ConnectionG

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ded

Neu

tral C

ondu

ctor

(Whi

te)

Gro

undi

ng C

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ctor

(Gre

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Blac

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Shore PowerCable




Shor

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PolarityIndicator



Circuit Breaker

Whi

teG

reen


120 VAC Device


Black Green White

Black

White

Green

Figs. 11-7a, b. Standard outlet for a three-pronged plug, showing which socket does what and the color of the wire going to it.

Fig. 11-6b. Here, a single-pole breaker (circled area) is allowed in the branch feeder to both the 120-volt AC appliance andthe outlet, because the boat is equipped with a polarity indicator. The breaker will only trip the black conductor. (© ABYC)

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Ground-Fault Circuit InterruptersGround-fault circuit interrupters (GFCIs) are a spe-cialized type of circuit breaker designed to trip openwhenever resistance between ground and the un-grounded conductor drops below 25,000 ohms. Anytime current is diverted from the white wire, such asthrough your body when you grab a hot AC wire, theGFCI senses the absence of grounding current andopens the circuit, hopefully in time to prevent allyour friends and relatives from having to make pre-mature calls to the florist.

Just as with home installations, boats are re-quired to have ground-fault circuit interrupter out-lets on certain branch circuits of the AC service. Thistype of outlet is easily identified by the test and re-set buttons located on the face plate. Many noviceelectricians assume that the purpose of GFCIs is toprotect the circuit or device a circuit is feeding. Notso! GFCIs are intended to protect people fromshock, not equipment.

GFCI protection is required in areas of the boatwhere excess moisture or a particular shock haz-ard may exist. Specifically, the ABYC recommends GFCIs in heads, galleys, engine rooms, and ondeck. For all practical purposes, this means you maywant a GFCI on every AC circuit on your boat.

In some cases, protection for all of these areas canbe provided by just one GFCI outlet, with conven-tional outlets installed “downstream” from the GFCI.To protect the other outlets downstream, the GFCImust be the first outlet in the circuit. On larger boats,this protection may be broken up into more than onecircuit, necessitating the use of several GFCI outlets.

Ignition Protection with GFCIsAll of this is of particular significance to boats that usegasoline as fuel and must meet ignition-protection re-quirements as discussed in chapter 4. Most GFCI out-lets are not rated for ignition protection and thereforeshould never be used in engine rooms. Marine-gradeGFCIs are available, but at considerable cost. This isreally no problem for either the boatbuilder or you ifyou intend to add an outlet in your boat’s engineroom. Simply use a conventional outlet in the spacerequiring ignition protection, and tie it into a GFCI

outlet mounted in a safe area, such as in the galley.Figure 11-8 illustrates how this arrangement shouldbe wired.

Testing GFCI OutletsAll GFCI outlets used on boats must be testedmonthly. The delicate internal mechanism of a GFCIoutlet used in the harsh marine environment cancorrode and cause the unit to not trip when you needit most. The simple test procedure is often over-looked, and not testing each outlet every month cancause obvious problems (it won’t work when it’s re-ally needed).

GFCI OUTLET

STANDARD OUTLET

TEST

RESET

Black

White

Green

Fig. 11-8. A GFCI outlet with a non-GFCI outlet wired in toshare protection.

167


To test a GFCI, simply depress the test button onthe assembly faceplate. This trips the internal breakerand actually exercises the outlet’s inner workings toensure that it’s functioning as it should. If the test andreset buttons feel spongy and seem to have lost theircrisp snap action, odds are good that the GFCI mech-anism is corroded, and the outlet should be replaced.

Another point worth mentioning here is that justbecause the dock box that your boat is connected to atthe marina is protected by GFCI (and it always shouldbe), you shouldn’t think that you’re protected fromshock hazard on your boat. These dockside GFCIs arelikely to be forgotten by the maintenance crew andnever tested until it’s too late. To be safe, always test thedockside outlets before you plug in your shore-powercord, and to eliminate any worry, upgrade your boatwith this important protection as soon as you can.

Checking Voltage, Continuity, and Polarity on AC CircuitsSooner or later, problems will crop up with the ACcircuits on your boat, and you’ll need to do basicmultimeter tests for voltage, polarity, and continuity.There is no need to be afraid of doing these tests onAC circuits, even for the novice, but following somebasic rules, in addition to the safety rules listed above,will ensure that you won’t damage your meter or endup having a shocking experience.

Besides your multimeter, several small, inexpen-sive testers can be extremely useful when workingaround AC systems. Figure 11-9 shows an LED outlet tester with a built-in GFCI test function, andfigure 11-10 shows an inductive voltage sensor usedfor verifying the presence of AC voltage, even behindpanels and through insulation. The LED outlet testeris useful in determining whether reverse polarity ex-ists and whether or not there is an open circuit in anyof the three conductors.

It is not at all uncommon for low voltage to be aproblem in an AC circuit, or reverse polarity for thatmatter. A disconnected green grounding conductoris quite common and can go unnoticed until some-one gets a shocking jolt. The good news here is that

these problems usually originate at the dock, not onthe boat, and it’s easy to check for them yourself.

Figure 11-10 demonstrates using the inductiveAC tester to see if there is voltage present at an outlet.If the tester’s LED flashes and it emits a steady beep-ing noise, AC is present in the circuit. The only remaining question is how much voltage. To deter-mine that, you’ll need your multimeter.

Fig. 11-9. An LED outlet tester.

Fig. 11-10. Using the inductive AC tester to check voltage atan outlet.

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Checking AC VoltageWhen using your multimeter to check for AC volts,you need to remember that AC and DC volts are dif-ferent as far as your meter is concerned. With eithervolts or amps, you must switch to the AC function onyour meter before making any checks. If your meter isself-scaling (auto-ranging), the next step is to simplyinsert the leads into the appropriate sockets and take adirect reading on the meter, as shown in figure 11-11.

Note that in the diagram the meter’s red lead isinserted into the smaller of the two slotted holes andthe meter’s black lead is inserted into the larger.Don’t forget to turn on the appropriate branchbreaker before making this test. If your meter is notself-scaling, make sure you select the appropriatescale for the voltage you’re expecting to read.

When verifying voltage at an appliance, a hot-water heater for example, that’s hard-wired into thecircuit (permanently installed rather than pluggedinto an outlet), you’ll need to get at the terminals inthe junction box on the appliance. With the branchbreaker for the appliance turned on, check forproper voltage at the appliance by touching your redmeter probe to the terminal on the black AC wireand the black meter probe to the terminal on thewhite AC wire. Simply take a direct reading. In fig-ure 11-12, the AC voltage supply to a typical marinehot-water heater is being verified.

A useful tip to help you when working with ACcircuit testing is to get two short lengths of heat-shrink tubing at your local supply house, one whiteand the other black. Shrink the black piece aroundthe red lead on your multimeter and the white piecearound the black lead. This will remind you that theblack lead on the AC is the positive and the black leadis the neutral when working with AC. It simply givesyou a quick color reference to work with.

Slight variations in your meter readings are thenorm when measuring AC voltage. In fact, a varia-tion of as much as plus or minus 10 percent of therated voltage is possible. If your dockmates are allusing the AC system feeding the marina simultane-ously, you can expect a lower voltage reading.

At peak usage times of the day (usually aroundbreakfast and dinner) you can also expect lowerreadings. AC generators on board could also con-ceivably run to that much of a variation. This vari-ation is not indicative of any particular problem

Black

Red

Fig. 11-11. Using a multimeter to check voltage at an outlet. Fig. 11-12. Using the multimeter to check voltage to a hot-water heater terminal block.

169


and will not affect the performance of your onboardequipment as long as the 10 percent variation at therated frequency (either 50 or 60 Hz) is not exceeded.By the way, multimeters that can read frequencyhave dropped considerably in price and are availablefor less than $50. If you’re going to work with ACregularly, this is a good added feature to have onyour meter.

Checking AC AmperageChecking AC amperage through a circuit can be abit tricky. The problem is that since sheathing pro-tects AC wiring through most of its length, it’s some-times tough to find a single conductor around whichto clamp your meter to take a reading. Rememberthat with an inductive clamp-type ammeter you canonly use one conductor to measure amperage. Thisapplies to both AC and DC. The truth is, this is not areading you’ll be making very often, because AC ap-pliances all provide the data needed to determineamperage. The need to actually measure amperage in AC systems is far less of an issue than it is with DC circuitry. Figure 11-13 shows an inductive ACclamp meter being used to determine current in anAC circuit.

AC Continuity TestsContinuity tests for AC circuits are more frequentlyneeded than are voltage and amperage tests, and theability to perform a good continuity test will be use-ful, especially when checking things like shore-power cords.

The most important point to remember whenchecking for continuity is to be certain the wiringthat you intend to check is disconnected from thepower source. The risk here goes beyond simplydamaging your multimeter; it’s also a shock hazard.Continuity tests can be used not only to determinethe integrity of wiring, but also to check some resis-tive AC appliances—things such as a hot-waterheater element or an electric coffee maker.

The Ed Sherman Wiggle TestWhen checking the conductor continuity in any flex-ible cord, such as a shore-power cord, it’s a good ideato perform what I call the wiggle test.

These cords take quite a beating and are fre-quently abused. It’s quite possible to get a solid con-tinuity reading with your meter and lose continuitywhen the cord is flexed, especially close to the endswhere the cord’s three conductors attach to the plugends. Figure 11-14 on page 170 shows a typical shore-power cord being wiggle-tested.

To do the Sherman wiggle, set your meter to theohms scale and connect one meter probe to theprong on the plug and the other probe to the corre-sponding socket at the other end of the cable. Youshould get a very low ohms reading, near zero if allis well. Next, bend and flex (i.e., wiggle) the plug andsocket ends while firmly holding the cable. Carefullyobserve your meter, and look for a change from a lowohms reading to an open-circuit reading of infinity,or “OL” on digital meters.

A fluctuating reading indicates a break in conti-nuity behind the insulation at the plug end. Check allthree conductors in this way to be sure they’re all OK.If any momentary break in continuity is indicated, asuitable replacement end will need to be installed onthe cord. Marinco, an electric supply company,makes quality replacement plugs and sockets that areavailable at all good marine supply houses.

Fig. 11-13. An inductive-current clamp used to check currenton an AC appliance.

170


AC Resistive Equipment ChecksTo determine if the heater element in a hot-waterheater (or any other appliance using a heating ele-ment) is OK, you can also perform a continuity test.First make certain that the breaker for the heater isoff, and verify that power is not present by using theinductive tester described earlier and shown in fig-ure 11-10 on page 167. Next, attach your meter to theblack and white leads, respectively, at the terminaljunction on the heater and check the resistance read-ing through the heating element.

A resistance reading is to be expected if all is well.If you get a reading of infinity or “OL” on your me-ter, the element has developed an open circuit insidethe heater, and the heater or the element will have tobe replaced.

Figure 11-15 shows this test being performed on agood element, with a typical resistance readingshown on the meter.

Selecting a DC-to-AC InverterPopular with the sailboat crowd for some time now,12-volt-DC-to-120-volt-AC inverters are also be-coming increasingly popular among owners of smallpowerboats. The reasons for this trend are quite sim-ple. Space on small boats is at a premium, so a gen-erator installation is usually out of the question. Cost

may also be a consideration. En-try into the silent world of in-verter power is considerably lessexpensive than purchasing a gen-erator. Noise and the exhaustfumes created by a generator aresimply undesirable if a better al-ternative exists. Further, many ofthe inverters available actuallywork in two directions, creatingthe AC you want and also actingas high-end, multistage batterychargers for use at the dock whenyou’re plugged into shore power.

At least for limited use, theDC-to-AC inverter has changedthe way many small-boat owners

satisfy their craving for AC power on board. Engi-neers have designed inverters that can produce as lit-tle as 50 watts to as much as 3,000 watts ofcontinuous power—more than enough for mostsmall powerboats.

Fig. 11-14. The “wiggle test” on a shore-power cord.

Fig. 11-15. A continuity test on a hot-water heater element.

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Selecting an InverterNothing comes without a price, and although theseelectronic marvels are quite capable of producing ad-equate AC power, they need a fairly substantial DCpower source to keep them running. This in itself canbe the limiting factor on some boats. Batteries areheavy, and they too take up space. When selectingan inverter and designing the system that will sup-port it, there are some important considerations youmust make to ensure your ultimate satisfaction.

Classically, people go through a period of denialabout their personal AC consumption whenever thetopic of inverters or generators comes up. Dailypower consumption is the key to sizing not only theinverter itself, but also the battery bank that’s goingto feed it. Use of an inverter on board ties into muchof the discussion throughout this book. Battery types,amp-hour ratings, reserve capacity, wattage—all ofthese factors must be given serious consideration ifyou hope to be successful with an inverter selectionand installation.

AC Need AnalysisThe first step in inverter consideration is to performan honest and accurate analysis of your daily AC us-age. If all you want is to occasionally recharge a lap-top computer or rechargeable electric-drill battery,your needs are minimal. You’ll be served well by oneof the small portable inverters on the market today.But, if you intend to run a TV, microwave oven, andpossibly a refrigeration system in addition to sup-plying outlets for use with things like hair dryers andcoffee makers, you’re going to need an inverter thatpacks some real punch. What this all boils down tois wattage and how many hours per day you’ll be us-ing these appliances.

Be sure to consider usage; many of the appliancesyou’ll be running from the inverter will be used in-termittently. If you’re going to be running a mi-crowave simultaneously with a coffee maker, yourtotal wattage needs could easily be as much as about2,500 watts. Your inverter will need to have the powerto deliver at least 2,500 watts in this scenario; thesmaller 1,000-watt inverter simply won’t do the job.

Determining the AC wattage you need is easy. Asalready stated, wattage, or possibly volts and amps,must be indicated on the appliance. If the value isgiven in volts and amps, simply multiply the voltageby the amperage to determine the wattage of the ap-pliance. Make a list of all the appliances you intend torun with the inverter, and pay particular attentionto the subtotals of gear you expect to run simultane-ously. If money is no object, simply add up thewattage for all the appliances you expect to use. Sizeyour inverter to handle all the possible loads you’llrun simultaneously.

The bottom line here? Don’t cheat! Remember, asalready stated, people tend to underrate their AC us-age, buy too-small inverters, and end up disap-pointed after all is said and done. This can’t beemphasized enough.

Figure 11-16 on page 172 shows a samplewattage load-analysis sheet for determining the sizeof the inverter to select based on wattage.

Next, you’ll need to make some decisions abouthow many hours each day you’ll be running the var-ious appliances listed in your inventory. This willhelp determine battery-bank size. You must alsotake into account the loss through the inverter as itperforms its magic. This loss is really a form of volt-age drop and represents the conversion of some ofthe DC to heat as it’s inverted. Typically, invertersare about 90 percent efficient, so you can expect tolose about 10 percent of the available amp-hoursfrom your supplying battery bank through the in-verter. That, and the fact that you really don’t wantto discharge even the best batteries much below 50percent of their capacity, should tell you that you’regoing to need some serious DC capacity (i.e., bigbatteries) to make this all work as it should.

Figure 11-17 on page 172 shows a typical amp-hour calculation table that should be used to deter-mine total amp-hour consumption between batterycharge cycles when plugged into shore power.

Once you have determined your daily amp-hourrequirements, you need to think about how manydays you might be away from shore power and howfrequently you’ll be charging your batteries with the

172


Amp-Hour Calculation Table for Inverter Battery-Bank Sizing

Use Time/Minutes-Hours Amp-Hours Used(Typical)

Appliance . . . . . . . . . . .5 min. . .15 min. . .30 min. . . .1 hr. . . . .2 hr. . . . .3 hr. . . . .8 hr. . . . .24 hr.

13-inch color TV . . . . . . . . . . . .0.5 . . . . . . .1 . . . . . . . .2 . . . . . . . .5 . . . . . . . .9 . . . . . . .14 . . . . . . .37 . . . . . .110VCR . . . . . . . . . . . . . . . . . . . .0.5 . . . . . . .1 . . . . . . . .2 . . . . . . . .5 . . . . . . . .9 . . . . . . .14 . . . . . . .37 . . . . . .110Curling iron . . . . . . . . . . . . . . .0.5 . . . . . . .1 . . . . . . . .2Table lamp . . . . . . . . . . . . . . . .1 . . . . . . . .2 . . . . . . . .5 . . . . . . . .9 . . . . . . .18 . . . . . . .28 . . . . . . .74 . . . . . .2213-cu. ft. refrigerator . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 . . . . . . . .5 . . . . . . . .9 . . . . . . .14 . . . . . . .37 . . . . . .110Blender . . . . . . . . . . . . . . . . . .2 . . . . . . . .7 . . . . . . .143⁄8-inch drill . . . . . . . . . . . . . . . .4 . . . . . . .12 . . . . . . .2320-cu. ft. refrigerator . . . . . . . . . . . . . . . . . . . . . . . . . . .12 . . . . . . .23 . . . . . . .46 . . . . . . .69 . . . . . .183 . . . . . .550Mid-size microwave . . . . . . . . . .7 . . . . . . .21 . . . . . . .41 . . . . . . .83 . . . . . .166 . . . . . .249Coffee maker . . . . . . . . . . . . . .8 . . . . . . .23 . . . . . . .46 . . . . . . .92 . . . . . .183Vacuum cleaner . . . . . . . . . . . . .8 . . . . . . .25 . . . . . . .50 . . . . . .101 . . . . . .202 . . . . . .302Full-size microwave . . . . . . . . . .12 . . . . . . .34 . . . . . . .69 . . . . . .138 . . . . . .275 . . . . . .413

Wattage Calculation WorksheetAppliance . . . . . . . . . . . . .Rated Wattage . . . Start-up Wattage

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total wattage

Use this table to list all of your AC appliances. Findout the wattage by checking the UL labeling on theappliance. Start-up wattage applies to appliancessuch as refrigeration devices (refrigerators, ice mak-ers, air conditioners). In the case of inverters, themedium- to larger-sized units all have an intermit-tent-output rating that’s usually more than twicethe rated continuous output in watts; this is to al-low for the needed start-up watt requirements ofthese appliances. Be sure to check the specifica-tions of the unit you’re working with to make sureits rating is adequate. In the case of generators, ifsized properly, a typical 20–30 percent overratingfor total maximum draw will take care of this mo-mentary need, especially since it’s unlikely thatyou’ll have all of your appliances running simulta-neously for an extended period of time.

Fig. 11-17. Amp-hour calculation table for determining the correct size of an inverter battery bank.

Fig. 11-16. Wattage load analysis sheet for inverter or generator selection.

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engine’s alternator while underway. If you expect tobe using this system for weekend jaunts at anchor,you must multiply everything by two. If you expectto be away from shore power for a week, multiply byseven, and so forth. Once this is done, go back tochapter 5 and refer to figure 5-2 on page 71, whichshows typical battery amp-hour ratings. Take a com-mon group 27 battery, for example. It has a typicalamp-hour rating of about 105 amps. You can onlyuse a little over 50 of these to prevent excessive bat-tery discharge, so if your daily consumption requires100 DC amps, you’ll need at least two of these group27 batteries for each day away from the dock.

Figure 11-18 shows two formulas for determiningbattery-bank size based on known amps or watts.Figure 11-19 lists some common AC appliances andtheir approximate wattage ratings.

Installing an InverterAfter determining inverter and battery-bank sizing,you may be considering the possibility of installingan inverter on your own. The truth is, to install allbut the simplest inverter with its own self-containedplug outlets goes well beyond the scope of this bookand certainly the abilities of the average boatowner.There are many considerations to make, and even ex-perienced electricians often overlook some of the finepoints of the ABYC’s recommendations for inverterinstallation. If you’re thinking of adding an inverterto your boat, the best bet is to try and find an ABYC-certified marine electrician. The certified tech will bequite familiar with all the nuances of inverter instal-lation, and the end result will be well worth the la-bor expense here.

Having said that, the list of general guidelines thatfollows will enable you to at least converse with aprofessional electrician intelligently to come up withan installation solution that satisfies your needs.

Presently no one makes an ignition-protected in-verter. The nature of the beast is that internalswitching must be accomplished during operation,and this switching process can create some arcing asthe unit is working. For this reason, extreme caremust be taken when selecting a location to mountthe unit. If your boat is gasoline fueled, the invertermust be located in a compartment outside the en-

gine room. Further complicating the issue is the factthat manufacturers of inverters prefer to have themmounted as close to the battery bank feeding them as possible. The reason for this is to minimize theeffects of voltage drop in the DC feeder wires to theinverter.

Minimal voltage drop is a must if the unit is goingto achieve the 90 percent efficiency mentioned ear-

Formula for DeterminingBattery-Bank Size(taking inverter inefficiency into consideration)

To find the amp-hours drawn from the batteries by any givenAC appliance powered by the inverter, you must find the ACamperage or wattage consumed and apply one of the equa-tions shown here.

DC Amp/Hours = AC amps × 10 × 1.1 × hours of useDC Amp/Hours = AC watts ÷ 12 × 1.1 × hours of use

Typical AC Appliance Wattage RequirementsAppliance . . . . . . . . . . . . . . . . . . . . . . .Wattage

Television . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80–100VCR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50Stereo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50Curling iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50Lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100Blender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3003⁄8-inch drill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .500Orbital sander . . . . . . . . . . . . . . . . . . . . . . . . . . . .500Ice maker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200Small refrigerator . . . . . . . . . . . . . . . . . . . . . . . . . .150Mid-size microwave . . . . . . . . . . . . . . . . . . . . . . . .900Hand-held vacuum . . . . . . . . . . . . . . . . . . . . . . . .1,100Hair dryer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1,500

Fig. 11-18. Battery-bank size determination.

Fig. 11-19. Common AC appliances and their wattage re-quirements.

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lier. Batteries give off explosive hydrogen gas whenbeing charged and so need to be well ventilated toremove this gas.

Mounting an inverter close to batteries in an un-ventilated compartment, such as under a V-berth, isnot a good choice unless adequate ventilation isadded to create sufficient air exchange. Also, the in-verter itself is heavy and must be securely mounted toa panel or bulkhead. Inverters must be kept cool tokeep the efficiency up and to ensure the long life ofthe inverter itself. So again, the ventilation issuecomes up. The inverter-location checklist that fol-lows highlights these key points.

� Inverters must be located in a compartment sepa-

rate from gasoline engines and tanks.

� Inverters must be located as close as possible to the

batteries.

� Inverters must be securely mounted to a bulkhead

and through-bolted with adequate backing wash-

ers.

� Inverters must be located in a well-ventilated loca-

tion to allow for cooling of the unit and to allow

any hydrogen gas that builds up as part of battery-

charging to escape.

Further considerations, once a suitable spot forthe inverter has been decidedupon, have to do with propercircuit protection and systemmonitoring.

As for overcurrent protec-tion, consider that both theAC and DC sides of the in-verter will need some form ofovercurrent protection in-stalled. The output side of theinverter may have a circuitbreaker built in, but it pays todouble-check. As for the DCside, protection will need tobe installed.

The special fuses (slow-blow) used for this purposeare generally not provided as

standard with the units, but are available as an optionfrom the inverter manufacturers. These fuses andholders are rated for extremely high amperage andare generally described as class “T” fuses. As for thelocation of these fuses, the 7–40–72 inch rule applies.Refer back to chapter 4 if you need to refresh yourmemory. Figure 11-20 shows this fuse installed in theDC positive feed to an inverter.

As for system monitoring, to comply with ABYCrecommendations your inverter will need to havesome form of indication installed in or very nearyour existing AC panel (or if none exists as yet, nearthe existing DC panel) to let folks know that an in-verter is installed on board, and when it’s on-line.This can be accomplished via the installation of avoltmeter, indicator light, or both. To simplify allthis, spend the extra money and buy the invertermanufacturer’s optional system monitor! You cancover all the compliance issues in one shot, and getsome features built into the dedicated system moni-tor that are extremely worthwhile. These monitorscan provide important data such as volts, amps,amp-hours consumed, and time remaining on thesupplying battery bank, to name just a few of the avail-able functions. Figure 11-21 on page 175 shows a typ-ical inverter-monitoring system. This one is a “Link”unit from Heart Interface, now part of Xantrex.

Fig. 11-20. A T-type fuse installed in an inverter DC feed cable.

175


Inverter WaveformOn the subject of voltage output, there is one addi-tional point that needs to be made regarding invert-ers. Most (but not all) inverters produce what isknown as a modified-square waveform. Shore-basedpower supplies, on the other hand, produce what isknown as a sine waveform. Early inverters produced astandard square waveform.

This technical mumbo-jumbo is all great infor-mation for electrical engineers and of little value toboatowners, except for several issues. First, oldersquare-wave inverters had trouble running thingslike TVs, microwave ovens, and older computers,and could even damage or destroy these appliances.Today’s modified-square-wave and true-sine-waveinverters have pretty much licked that problem, andthe new inverters run just about anything.

The second problem caused by waveform is mea-suring voltage and amperage. As I mentioned earlierin this chapter and in chapter 3, the meter used tomeasure voltage from an inverter should be of thetrue RMS variety to give the best results. Typically,modified-sine-wave inverters will show low voltagewhen measured with an average-responding meter.This is no cause for alarm and not indicative of a faultwith the inverter!

AC GeneratorsJust as with inverters, advanced trou-bleshooting and installation procedures forAC generators go way beyond the scope ofthis book. These things are best left to theABYC-certified professional marine electri-cian. However, some general knowledge ofthese workhorses is still important for theboatowner and will help to ensure thatyour generator is of the proper size and isperforming as it should. The basic trou-bleshooting checklist at the end of this sec-tion will help you to at least point theservice technician in the right direction ifyou do have trouble with your generator.

Rating AC GeneratorsAC generators are rated the same way in-verters are. Wattage is the key here, and

the basic AC use-analysis chart for inverters willwork just as well for determining your generator re-quirements.

The essential difference between generator andinverter ratings is that typically, generator manufac-turers have rated their units in kilowatts (kW). Onekilowatt equals 1,000 watts, so, for example, if yourgenerator is rated at 4.5 kW, it’s a 4,500-watt unit.

As with inverters, boaters are inclined to over- orunderrate their needs with generators. Underratingwill give poor electrical performance, for what shouldbe obvious reasons by now. But a point that manypeople don’t realize is that overrating of a generatorcan wreak havoc with the generator itself. Generatorsare designed to operate at a very specific rpm to gov-ern and control the AC frequency. They must be ableto maintain this rpm over the entire operating rangeof the unit under all levels of electrical load.

The problem is just that—load. Underworkedgenerators will simply freewheel along, eventuallygumming up the cylinders, valves, and rings of the en-gine. Slight overrating in terms of average combinedwattage consumption is OK, but manufacturers rec-ommend that a generator be rated to average 75 per-cent of its total wattage most of the time. Knowingthis, it should be clear that running a TV from even

Fig. 11-21. A typical inverter monitoring panel, the Xantrex “Link” 1000.

176


the smallest generator will damage the unit if that’sthe only draw for extended periods. Generators arereally only suitable for fairly serious AC loads (such aselectric ranges, air conditioners, and hot-waterheaters) all running simultaneously and for extendedperiods of at least and hour or so—for example, dur-ing preparation for the evening meal.

Other serious disadvantages of generators includethe noise of the engine, those wonderful exhaust fumespermeating into the pre-dinner cocktail hour, andsimply having one more engine on board to maintain.

As already mentioned, both the voltage and fre-quency of AC generators are carefully controlled byan engine-mounted governor that keeps engine rpmstable under all electrical loads. If you have a genera-tor on your boat, your AC panel must have a volt-meter to be in compliance with the ABYC standards.It’s a good idea from time to time to monitor thisgauge. Any variation in voltage beyond 10 percentof the normal rated output for the generator that’sindicated by this gauge is an indication of trouble.

Modern generators are commonly regulated tocontrol voltage to as little as plus or minus 2 percentif all is well with the unit. As voltage fluctuates, so toodoes frequency. Normal frequency here in the UnitedStates is 60 Hz. Some of the better multimeters on themarket have the ability to measure fre-quency, and this is not a bad feature tohave if your boat has a generator installedor you’re thinking of having one added.

Measuring Generator OutputVerifying generator voltage and fre-quency is not difficult, but to ensurethat any low-voltage indications onyour AC panel are not due to a wiringand voltage-drop problem between thegenerator and the panel, measurementshould be done right at the output ter-minals on the generator. When check-ing voltage and amperage at thegenerator, be careful of moving partsand the hot exhaust on the generator,and be sure to take your readings at thecorrect location as per the instructions

from the generator manufacturer. If in doubt, makesure you have the service manual at hand, and use it!Figure 11-22 shows the frequency being verified on atypical marine generator.

Generator SafetyOver the years, marine AC generators have evolvedinto quite sophisticated pieces of equipment, and as aresult the safety features available today are extensive.Built-in sensors shut down the generator in the eventof such things as low oil pressure, engine or exhaust-system overheating, and even excessive exhaust back-pressure on some models. The problem is, differentmanufacturers use different systems, and features willvary even from one model to another from the samemanufacturer. To familiarize yourself with your gen-erator, get out the owner’s manual, and if you intendto do any but the most basic service or troubleshoot-ing on the unit, get the workshop manual as well.

Most inadvertent generator shutdown problemsare due to loose connections, low oil pressure (isthere oil in the engine?), or an overheating engine.You may have to trace through the cooling-systemtroubleshooting section of your workshop manual tofind the solution and get the generator up and run-ning again.

Fig. 11-22. Checking frequency with the multimeter.

177


AC Generator Troubleshooting GuideAside from these basic checks, some more advancedprocedures are found in the following checklist.These additional checks are too advanced for mostbeginners and will have to be carried out by a trainedtechnician, preferably one certified on your particu-lar brand of generator.

Low Voltage

� Check the voltage at the generator. If the reading

is OK and your panel meter is reading low, there is

an excessive voltage drop in the wiring between the

generator and the panel.

� Verify correct generator engine rpm and governor

settings.

� Check all connections and wire terminations for

integrity. First make sure the generator is off!

� If voltage is OK until the engine warms up and

loads are applied, the generator voltage regulator

and related circuitry are at fault.

� The voltage regulator may need adjustment or re-

placement.

High Voltage

� Check the frequency for normal range (between

57 and 63 Hz in the United States).

� If possible, adjust the voltage regulator.

� Verify correct engine rpm and governor adjust-

ments.

Erratic Voltage

� The generator brushes could be worn or burned.

� There could be internal wiring problems or loose

connections.

Erratic Frequency

� Check for loads cycling where the generator turns

the current on and off.

� If the frequency is erratic with all loads turned off,

check the governor for proper operation. Can you

hear subtle rpm changes?

High Frequency

� Have the governor operation checked.

Low Frequency

� Turn off all loads. If frequency returns to normal,

the generator is being overworked and is probably

underrated. Either give up some AC toys or pre-

pare to upgrade to a bigger generator.

� Check for faulty governor adjustment.

Galvanic IsolatorsA device that has become increasingly popularin recent years on new boats is the galvanic iso-lator. The trouble with them is that most folks,including many marine electricians, haven’t thefaintest idea what they do. So, what are thesethings used for anyhow? Well, here’s the defin-ition: “A device installed in series with thegreen grounding conductor of the shore-powercable which effectively blocks galvanic currentflow (DC), but permits the passage of alternat-ing current (AC).”

You’re probably still wondering, Yeah, but whatdoes it do? Why do I need one?

If you spend much time at the dock plugged intoshore power, you need a galvanic isolator. Here’swhy: Galvanic current flow is a danger at any marina,putting your boat at risk of galvanic corrosion.The more boats with AC shore power, the greaterthe risk. Your boat could be in great electrical shape,but once plugged into shore power it becomes elec-trically connected to its neighbors via the greengrounding wire in the AC system. This connectioncompletes an electrical circuit between multipleboats, each with potentially dissimilar underwatermetals exposed to the surrounding seawater. What’screated is a giant battery and the potential galvaniccorrosion that can result. Further, it is also possibleto transfer higher-voltage DC stray current from one

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boat to another in this situation. This could generatestray-current corrosion.

How can that be? You might have thought theAC and DC systems were completely separated onyour boat. They are, except for one common pointwhere the DC and AC grounding system are tied to-gether. Any faults that induce current flow in thisnormally non-current-carrying conductor can po-tentially be transferred via this green wire. This straycurrent can cause excess corrosion, rapid deteriora-tion of underwater sacrificial zincs, and, in the worstcase, can cause underwater metal appendages fromyour boat to literally dissolve in seawater. A com-mon cause of stray-current corrosion is wiring thatuses a boat’s electrical bonding system as the DCground for various appliances—typically bilgepumps. Any live wire hanging in the bilge watercould be the culprit.

The only direct path for stray current to flow be-yond any individual boat is via the green groundingconductor in the AC shore-power system (that is, ex-cept for a leak into the water surrounding the boat).It’s important to note that the galvanic isolator is de-signed to isolate only low-level galvanic DC current.

Its purpose is to block only about 1.4 volts or less, nota full 12 volts. All precautions must be taken to en-sure this green wire never has high-level current try-ing to find ground through it unless an AC systemfault occurs. The isolator is intended to block onlythe natural galvanic current that will try to pass dueto the electrically connected dissimilar underwatermetals discussed.

The isolator uses four heavy-duty diodes, oftencombined with a capacitor, to absorb any voltagesurges that may occur. These diodes use their inher-ent resistance and one-way capability to effectivelyblock any small amounts of DC flow. (Galvanic cur-rent is measured at less than 1,200 millivolts, or 1.2volts.) If a fault in the boat’s AC system develops andthe green conductor must be put into real service, ACcan easily overcome this resistance and will flowthrough the isolator.

Remember that the green wire is designed to pro-tect against shock, and its integrity is of paramountimportance. Since the isolator is mounted in serieswith the green wire as the first stop past the shore-power connector on your boat and is often not easilyaccessible, the isolator’s integrity must be known at

all times. A blown diode inside theisolator could have the same effect asclipping off the third grounding ter-minal on an extension cord, as men-tioned earlier.

In consideration of all this, thecurrent version of ABYC Standard A-28, Galvanic Isolators, mandates astatus-monitoring device for a gal-vanic isolator. Both Guest and ProMariner make such devices,which consist of a remote panel thatalarms if a failure occurs. These mon-itors also seem to do a very good jobof identifying other electrical prob-lems, often with the dock wiring theboat is plugged into. This has beensuch a problem that an ABYC com-mittee is now considering a new typeof isolator that is rated as electrically“fail safe,” meaning that if a diodeFig. 11-23. A ProMariner galvanic isolator.

179


fails, electrical continuity through the device cannotbe compromised. As of this writing, the committeehas not finalized a new draft of the standard for re-view. Rest assured that boating magazines will pub-licize the final decision.

If you’re uncertain whether your boat even has agalvanic isolator, check with your dealer. If you canget at the wiring on the back side of your shore-power inlet, trace the green wire through to the ACmaster panel. If the boat has an isolator, it will bemounted here. Figure 11-23 shows a ProMariner gal-vanic isolator, which uses a capacitor, installed on thegreen wire.

Testing Galvanic IsolatorsA simple test to make sure your galvanic isolator isworking as it should, once you’re certain you haveone, is to use the LED tester shown in figure 11-9 onpage 167 to determine ifan open circuit exists inthe grounding conduc-tor.

If all the connectionsand the wiring are intactbetween your AC paneland the shore-powerbox, an open indicates ei-ther a break in continuityinside the galvanic isola-tor or a problem on thedock. Have the marinaoperator verify the con-dition on the dock. If it’sOK, you may have afaulty galvanic isolator.Any ABYC-certified elec-trical technician cancheck this for you if youhave any doubts.

Figure 11-24 showsthe correct location forthe galvanic isolator inrelation to your shore-power inlet and the ACpanel on your boat. If

your boat doesn’t have a galvanic isolator installedand you spend a lot of time at the dock, it would bea good upgrade to any AC electrical system. You cando this one yourself rather easily. Just make sure thatthe isolator you select is rated for the proper amper-age (at least the same as your boat’s AC rating ormore), and preferably with a built-in capacitor foradded protection to the unit itself. Also rememberto mount these units in a spot that’s relatively easyto get at and will offer good ventilation.

Remember that this chapter is not intended tomake you an expert high-voltage electrician. It’s in-tended to give you a little confidence for basic sys-tem checks and to enable you to talk with a marineelectrician as an informed consumer. If you still getnervous around shore power, stay away from it! Callin the experts.

Und

ergr

ound

Con

duct

or (B

lack

)

ShoreConnection

Gro

unde

d N

eutra

l Con

duct

or (W

hite

)

Gro

undi

ng C

ondu

ctor

(Gre

en)


Shore PowerCable




Shor

e Si

deBo

at s

ide




Circuit Breaker

Transfer SwitchGEN–OFF–SHORE

Blac

kW

hite

Gre

en

120 VAC Grounding

Type Receptacle


GeneratorMain Circuit

Breaker

120 VAC Generator

Fig. 11-24. Diagram of the galvanic isolator between the shore inlet and the AC distributionpanel. The galvanic isolator must always be the first device installed in series with the greenwire as it enters your boat. (© ABYC)

Installing Marine Electronic EquipmentChapter 12

Electronic GadgetrySometimes it seems like powerboaters are theworld’s greatest gadgeteers. We who own boats lovethe electronic devices that we install on or attach tothem, and from time to time (as we can afford it)one of our most pleasurable tasks is the selection,purchase, and installation of the latest piece of elec-tronic gadgetry. Few indeed are the boaters amongus who fail to install some new electronic wonderon our boats at least once a year.

My current West Marine catalog is more than 1inch thick, and the lavishly illustrated pages are repletewith images of all manner of electronic doohickeys, allof which, with very little imagination, can become es-sential to the safe and efficient operation of my boat.There are no less than 26 pages of marine radios andaccessories, 10 pages devoted to GPS receivers, 12pages of electronic chart plotters and navigation soft-ware, 6 pages of radar, and an entire section on light-ing. Of course, you can view the entire catalog onlinethese days, at www.westmarine.com.

You can even buy a remote-control underwatervideo camera with a 131-foot cable for a mere$5,999. Would I have one of these video cameras onmy boat? You bet I would, and all that other stuff,too. Like nearly all boaters, if it weren’t for the con-straints of a small budget and a lot of common sense,I would need a bigger boat just to carry all the gad-gets that I would like to install on it. All this won-derful stuff would help me navigate more safely, findthat elusive lunker fish, or communicate with fel-low boaters or friends on shore.

Installing Your Own ElectronicsMost aftermarket electronic accessories for boats areexpensive; some (such as new radar or that videocamera mentioned above) are very expensive. Butone of the best ways to reduce the financial shock ofnew electronics is by doing the installation yourself.

Fortunately, this is a fairly easy task, and with thenever-ending advances in equipment, the immediateresults can be quite gratifying, provided you takeinto consideration certain factors that ensure aproper installation.

Universal Installation DetailsDepending on whether you’re installing a depth-sounder, a fish-finder, a VHF radio, a GPS receiver,or radar, many of the nuances of installing new elec-tronics will vary, but the basic procedures for mostnew equipment are similar, with certain considera-tions in common: magnetic fields, radio-frequencyinterference (RFI), and the power supply. Let’s takea look at these three items one at a time.

Magnetic-Field IssueOne thing that is often taken lightly but is of extremeimportance is the initial decision of where to mountyour new equipment. Besides the obvious ergonomicconsiderations of seeing the screen or controls on thenew device and perhaps keeping it from gettingsprayed with water while underway, stray magnet-ism is a major concern. Today’s small powerboatshave relatively small consoles to work with and al-most always have a compass mounted right in themiddle of the area just in front of the helm. This isusually right where you want to mount that new ra-dio or fish-finder to keep it in plain view and easyto use.

Virtually all of the electronic equipment you’relikely to want on board emits some amount of mag-netism. (Remember from chapter 3 how any currentflowing through a conductor creates a magneticfield?) This magnetism is sure to upset the accuracyof your compass, and in some cases this compass er-ror can be quite pronounced.

Several years ago, without giving the locationmuch thought, I installed a new VHF radio on my

180


www.westmarine.com

boat. I put it about 8 inches from my steering com-pass, right where the old one had been. The new ra-dio worked just fine. I could see the controls, theywere easy to reach when I wanted to transmit, andthe speaker was close by so I could easily hear anyincoming transmission. The problem with my com-pass didn’t show up until several weeks later when Iwas traveling in fog and had to use my GPS to navi-gate to the breakwater entrance to my homeport. Iknew the GPS waypoint was accurate, so all I had todo was follow the compass course to the entrance. Itwas then that I discovered that my compass was 14degrees off! Sure enough, the new VHF speakers hadmuch larger magnets in them than my originalspeakers had, and the magnetic field they generatedwas sending my compass haywire!

Zone of Magnetic SeparationThe bottom line here is quite simple: You mustmaintain a zone of separation between your compassand any new electronic gear you install. The prob-lem I had with my compass was caused by the newradio being too close to it. Ideally, in my experience,a separation of about 16 inches does the trick, butwith highly magnetic equipment such as powerfulspeakers or radar, that zone of separation can con-ceivably extend to 3 feet or more.

You might be thinking that with your boat a 16-inch zone of separation is impossible; your con-sole just doesn’t allow that kind of room. Well,that’s OK; a simple test is all that’s needed to deter-mine if you can close the zone. Temporarily powerup the equipment and move it near the compasswhile looking for any deviation in the compass dial.By slowly and carefully moving the activated equip-ment closer to the compass, you can establish theactual minimum zone of separation for that partic-ular piece of gear. Keep in mind that in some casesany device, such as one with a magnetic speaker, canhave a profound effect on compass deviation with-out even being switched on.

In my experience, Loran and GPS receivers havevirtually no effect on compasses. LCD fish-findersalso seem to be fairly harmless in close proximity tocompasses. (However, their CRT brothers can emit

a serious amount of magnetic interference.) Regard-less, you should always check to be sure. (Note:Never “key” the mike on a VHF radio as part of thistest. Keying the mike on a VHF radio with the an-tenna disconnected can damage the transmitter inthe radio.)

Figure 12-1 shows the compass deviation beingchecked with a set of alligator-clip jumper leads thattemporarily connect the device to a battery. (Thesejumpers are part of your basic tool kit from chapter 1.)

Radio-Frequency Interference (RFI)Another thing to consider when installing certainelectrical devices, such as battery chargers and in-verters, on board is what is known as radio-frequencyinterference (RFI). Things like alternators and faultyignition systems can also emit RFI. You may haveheard one of the effects of RFI, caused by faults likea cracked distributor cap or a bad spark-plug wire,as static over an AM/FM radio. Ignition-induced RFIchanges pitch in direct proportion to engine rpm.

181

Installing Marine Electronic Equipment

Fig. 12-1. Checking compass deviation with a temporaryhookup to an electronic instrument.

182


An easy way to isolate RFI is with a small portabletransistor radio. Simply tune the radio between twoAM stations (FM stations don’t work as well), andyou’re ready to go. Turn on the electrical compo-nent you want to check, and listen for a loud humfrom the radio. Move the radio alternately closer,then farther away from the component you’re check-ing, and listen for a change in the humming noise. Agood device to try this with for the first time is a bat-tery charger. I have not found one yet that did notemit some RFI; it’s quite normal for these devices.

The problem with RFI is that it can affect thingslike electronic compasses, autopilots, and Loran-Csystems, and you’ll never hear a sound. However, youcould end up in Timbuktu instead of your favoritefishing hot spot!

Like the magnetism problem already discussed,you’ll need to ensure that a good zone of separationis kept between devices that cause RFI and devicessensitive to it. For ignition systems and alternators, avariety of suppression devices and filters are avail-able, and they are easy to install. All come with sim-ple instructions. Check your local NAPA Auto Partsstore or a good marine electronics distributor to getthe parts for this job.

With inverters and battery chargers, you can es-tablish the zone of separation you need using thetransistor-radio method described above. Simplymove the radio away from the activated device inquestion until no noise is heard, and your zone ofseparation will have been established. If you’re do-ing this test with a battery charger or inverter, makesure the device is not only on but also under full loador output, whichever the case may be. RFI emissionwill vary proportionally with the amount of electricalactivity within the device. In all cases it’s advisableto consult the manufacturer of any electronic deviceyou intend to install and find out about its sensitiv-ity to RFI. While you’re at it, get any recommenda-tions they may have regarding separation zones andRFI suppression methods.

Power SupplyVirtually all small-boat electronic equipment avail-able today requires only a positive and a negative lead

to get the basic unit running. Some sensitive elec-tronic equipment housed in metal cases may requirea chassis ground (green wire) in addition to the neg-ative lead (yellow or black wire). Still other equip-ment may have an additional hot lead (red wire) topower an internal memory. This extra lead must getpower at all times and must not be switched in anyway. If you have any doubt about how these leadsshould be connected, refer to the installation instruc-tions for the particular equipment in question.

Remember, unlike things such as incandescentcabin lights, most new electronic gear is polarity sen-sitive. This means if you inadvertently switch the pos-itive and the negative wires when you connect themto your power source, you could severely damage theequipment. Most manufacturers supply a red and ablack lead with their equipment, indicating DC pos-itive and negative, although white and black wires arestill widely used. Always refer to the equipment in-stallation instructions to be absolutely certain!

With the exception of VHF and single-sideband(SSB) radios and radar units, the amperage re-quirements for most new electronics are compara-tively low, so wire gauge is not too much of anissue. Generally, on small boats, the length of thewire between the distribution panel and the equip-ment is not that long, so sticking with the samegauge wire supplied with the equipment (usually 16AWG) will suffice.

Figure 12-2 shows a typical wire harness with anin-line fuse installed, as supplied with a Loran-Cunit.

As for the connection to your boat, it’s best todedicate a circuit breaker at your DC distributionpanel for instruments and designate separate positiveand negative bus bars to connect your various piecesof equipment. Not only can direct connections toyour batteries be messy, but they will add to thelength of wire needed to power-up your electronicgear. Figure 12-3 on page 183 illustrates the bestmethod to supply your equipment, by creating a ded-icated branch bus from your main distribution panel.This way you can use bus bars that are adequatelysized, and the addition of more equipment later onwill be a much simpler task.

Once your new gear is mounted where you want it,

183


the next steps are specific to thevarious types of equipment. Nowyou have to think about otherthings, such as antenna or trans-ducer placement.

Installing a VHF RadioYour VHF radio should be themainstay of your onboard com-munication system. Although cellphones have become popular in re-cent years, the best way to get helpwhen the chips are down is still viaVHF radio transmission. For thisreason, the VHF radio needs to beinstalled safely. You may need itwhen things aren’t going so well onyour boat.

DC -

DC +

DC Panel DC + ToElectronicEquipment

DC - FromElectronicEquipment

Positive Bus

Negative Bus

Fig. 12-2. A typical factory harness, with in-line fuse holder installed.

Fig. 12-3. Dedicated bus bars to supply electronic equipment branched off the main distribution panel.

184


Remember that transmission power with a VHFradio is proportional to the power supplying the ra-dio. While transmitting, VHF power needs are ap-proximately four times greater than when the radio isreceiving. You may need to use the radio when max-imum battery power isn’t available; the very reasonfor your call for help could be that your batterieshave drained enough so you can’t get your enginestarted. Poor-quality connections and undersizedwires supplying the VHF could induce excess volt-age drop to the transmitter, so be sure this end of theinstallation is absolutely first-class!

Your next concern is the line-of-sight nature ofVHF radio signals. The higher your radio antenna ismounted, the greater will be the effective range of theradio. So, when considering where to mount the an-tenna on your boat, try to get it as high as possible. Ifyou venture far offshore, you may even want to con-sider one of the antenna mast extensions availablefrom Shakespeare and others as a means of gettingyour antenna as high as it will go. The table in figure12-4 shows the approximate range you can expect fora 25-watt VHF radio, based on antenna height.

How Much Can I Gain?Antenna gain is another important considerationwhen trying to decide which VHF antenna to pur-chase. Gain describes the power amplification avail-able through your antenna, which refocuses theimpedance of the antenna so that instead of trans-mitting a large portion of the signal up into the skyand down into the water, more of the signal is di-rected out toward the horizon where it’s much morelikely to do some good. Gain is measured in decibels(dBs), a logarithmic measure of sound and noise(plus a few other things that don’t concern us here).

Even though the Federal Communications Com-mission (FCC) regulates the output of VHF marineradios to a maximum of 25 watts, the effective radi-ated power of the radio can be greatly increased byinstalling an antenna with a higher gain. (The gainof an antenna is fixed and can’t be adjusted.) As anantenna’s dB rating increases, its radiated beam getsnarrower or flatter, so that an antenna with a very

high gain will have a pancake-shaped radiation pat-tern oriented flat with the surface of the Earth. Thiscan have a profound effect on your radio’s transmitrange without increasing the transmission power, buttoo much gain can work against you, especially ifyou’re pitching and rolling in a rough sea.

The three commonly available antenna dB rat-ings for boats are 3, 6, and 9 dB. Figure 12-5 on page185 illustrates their approximate radiated wave pat-terns. Notice that the 3-dB antenna is radiating abroader pattern than the 6- and 9-dB antennas. Forthis reason, a masthead-mounted 3-dB antenna isthe best choice for most sailboats. If the 6- or 9-dB an-tennas were to be used, the sailboat’s radiated signalwhile heeled underway would either be aimed at themoon or the bottom of the ocean. The best compro-mise for a small powerboat is the 6-dB antenna. It willprovide the maximum range with a minimumamount of signal lost due to the boat rolling in a sea-way.

For extended range, many powerboats with dualstations will mount a 9-dB antenna for the radio onthe upper station, which is more likely to be used ina calm sea. The radio in the lower station, which ismore likely to be used in rough conditions, will havea 6- or even a 3-dB antenna for extra reliability whilethe boat is pitching and rolling.

The Coaxial QuestionBesides the effects of antenna placement and thepower supply to your VHF, you should also consider

Transmitting Antenna Receiving Antenna HeightHeight

5 ft. 10 ft. 25 ft. 100 ft. 250 ft.

5 ft. 5 mi. 7 mi. 9 mi. 15 mi. 23 mi.10 ft. 9 mi. 10 mi. 11 mi. 18 mi. 25 mi.30 ft. 10 mi. 12 mi. 13 mi. 20 mi. 28 mi.60 ft. 12 mi. 14 mi. 15 mi. 21 mi. 30 mi.

Fig. 12-4. Antenna height versus VHF range.

185


the type of cable connecting your antenna to yourradio. Also, when selecting an antenna, look carefullyat the factory lead coming from the base of the an-tenna; it should be of quality coaxial cable (describedbelow). If not, after reading this section you may de-cide on a different antenna. The coaxial lead shouldnot be the only criterion used for antenna selection,however. Internal construction and a quality platedbrass base mount are also considerations.

Coaxial cable (coax) is designed to conduct trans-mitted and received energy between your antennaand radio. Coaxial cable is a two-conductor cablewith a center that you can think of as the “positive”conductor. The next outermost layer of typical“coax” cable is an insulation layer used to keep thewoven ground conductor separated from the centerconductor. This outer conductor is sheathed by theouter “skin” of the cable. Just as with any wiring onboard, the quality and amount of energy lost throughthis cable will affect the performance of the radio. Inthis case the loss is measured in dB rather than thevoltage drop mentioned throughout this book. Thebest advice is to use the largest coax you can to min-imize signal loss. Always install a high-quality lead onany antenna you buy.

There are three common kinds of coaxial cableavailable today: RG-58, RG-8X, and RG-8U. Just aswith regular wiring, the signal loss is proportional tothe length of wire. For most small powerboats, the

wire won’t be much more than 20 feet long, so theloss will be minimal. The table in figure 12-6 com-pares the dB signal loss for a 20- and a 40-foot cablerun using each of the cable types mentioned here. No-tice that the loss in dB between the RG-58 and theRG-8U cable is more than double, even for a fairlyshort 20-foot cable run.

Besides the basic types, coaxial cable comes in dif-ferent construction configurations, and these canmake a difference in the long-term performance ofthe cable. Coaxial is basically a two-conductor ele-ment separated by a PVC insulator. For best long-term results, the center conductor should be oftinned, stranded copper. The second conductor is thebraided outer shield, which should also be of tinnedcopper. Many manufacturers try and save a few dol-lars by using a solid, single-strand untinned centerconductor and untinned shield. This type of coaxworks just fine for cable TV installations at home, butit’s not a good choice for marine VHF installations.

Cable SplicesProbably the biggest source of VHF radio problemsarises out of a corroded antenna connection, either atthe radio or at any point in the antenna lead where asplice is installed to extend the lead. For a simple so-lution to this problem, apply a light coating of sili-cone lubricant to the center stud and threads of thebarrel on the connector itself before screwing it intoplace. This will provide a good watertight seal andkeep the green gremlins (corrosion) away. Regard-less, these connections should be checked at leastonce each boating season to ensure that no corrosion

Coax Type versus Signal Loss in dBCable . . . . . . . . . . .20 ft. . . . . . . . . . . . . .40 ft.

RG-58 . . . . . . . . . . . . . 1.2 . . . . . . . . . . . . . . . 2.4RG-8X . . . . . . . . . . . . . 0.9 . . . . . . . . . . . . . . . 1.8RG-8U . . . . . . . . . . . . . 0.5 . . . . . . . . . . . . . . . 1.0

9db

3db 6db

Fig. 12-5. Wave patterns radiated by 3-dB, 6-dB, and 9-dBantennas.

Fig. 12-6. Signal loss (in dB) for cable runs of 20 and 40feet, using three popular grades of coaxial cable.

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exists. Corrosion here will definitely create inferiorVHF performance.

Eventually you may need to replace one of thesecoax connectors (known as PL-259 connectors). Hap-pily, a recent breakthrough in design has eliminatedvirtually all of the difficulty normally associated withthis task. With a standard connector you must care-fully strip back precise, staggered lengths of each ofthe three layers of coaxial cable down to the centercore. Once this is done, you carefully insert the coax-ial into the connector and either solder both the cen-ter core to the center pin and the braided conductorto the outer body of the assembly, or use special

sleeves to compress all of the components of the coax-ial into place. With the new solderless connectors, allyou do is to cut the end of the coaxial cable square,firmly push the cable into the new connector, squeezetogether the locking arms, and thread on the outercover of the connector. These connectors are sold asCenterpin PL-259-CP connectors, and truly take thework out of this usually finicky task, shown in ffigure12-7. Figure 12-8 gives a complete VHF installationoverview from the DC distribution panel to the radioand from the antenna to the radio.

As a final note to these instructions for VHF in-stallation and general use, remember to check yourradio on an appropriate channel each time you takeyour boat out. This is not at all frivolous. In my ex-perience, most failures with VHF radios occur onthe transmitter side of the circuitry, not on the re-ceiver side. So simply turning on your radio and lis-tening to the chatter on various stations is noassurance that the radio will work as it should if theneed to call for help ever arises. Be certain; alwayscheck for both transmission and reception beforeleaving the dock. Remember, your VHF is an im-portant safety tool, not a toy. Respect and use properradio etiquette at all times. You’ll greatly appreciatethis minor formality if you ever do need to use yourradio in an emergency!

Installing a Fish-Finder or Depth-SounderIn terms of functionality, the latest ver-sions of LCD and CRT fish-finders arereally outstanding. The performancegains over the last 10 years with this typeof equipment have been just phenome-nal, and prices for quality gear have actu-ally gone down for even the mostadvanced, feature-packed units. But, inthe same vein as VHF radio perfor-mance, these fish-finders are only asgood as the information getting to andfrom them. Think of the fish-finder ordepth-sounder transducer as a two-wayantenna that must send and receive

DC -

DC +

DC Panel

DC - FromElectronicEquipment

Coaxial Cable

VHF

In-Line Fuse

Antenna

Fig. 12-7. A Centerpin PL-259-CP coaxial (coax) connector.

Fig. 12-8. Overview of a complete VHF radio installation.

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signals. Rather than shooting through the air, as doVHF signals, these signals leave the underside of yourboat, bounce off the bottom of the waterway, thenget back to the transducer where they are translatedinto water depth. This is how you spot “ol’ silver-sides” hiding in a clump of weeds 10 feet off the portside of your boat.

As with your VHF installation, you must considerany magnetic fields emitting from the control unitof the fish-finder or depth-sounder that could affectyour compass. This is of particular concern if youhave selected a cathode-ray-tube (CRT) instead of aliquid-crystal-display (LCD) device. By their nature,CRT fish-finders emit magnetism right through theface of the screen, so be sure to check this out, as de-scribed earlier in this chapter, before mounting itclose to your compass.

Once you decide where to put your fish-finder ordepth-sounder, make a DC positive and negative con-nection for powering it. The best bet is to hook it upto a dedicated bus bar. Refer to figure 12-3 on page183 to refresh your memory on how this is done.Don’t forget that, depending on the manufacturer,you may need an additional grounding lead to theunit’s case. Be sure to check your installation manualto determine this. (Note: An easy way tofigure this out is to look for a threadedstud with a wingnut on it at the back ofthe instrument. This is the grounding lug.)

Transducer Mounting and TroubleshootingRegardless of which brand of fish-finderyou have, you’ll have three choices fortransducer mounting. But, if you wish tohave the water-temperature-monitoringcapability that comes with most topbrands available today, you’ll be limitedto two of the three mounting options.

No matter which mounting methodyou decide to use, you must give yourtransducer a clear view below the boatthat will not be clouded while underwayby air bubbles or momentary separationof the hull from the water. For power-

boats the transducer should end up toward the rearof the boat at a point on the hull where the bottom issubmerged at all speeds and under all normal seaconditions. You should also consider the noise, theair bubbles and turbulence generated by propellersand lifting strakes built into the hull. This interfer-ence can reduce transducer performance.

As a general rule, try to mount the transducer atleast 18 inches (about 46 cm) away from the pro-peller. The face of the transducer should also be in-ward of the first lifting strake on the bottom of thehull by about 3 to 6 inches (7.6 to 15 cm). If yourboat has a skeg or keel, mount the transducer about12 inches (30 cm) to the side of the keel. This is not tominimize the effect of turbulence but to ensure thatthe transducer’s conical beam is not partially blockedby the keel, reducing its performance. Figure 12-9illustrates all of the dimensions outlined here.

One additional consideration, besides the orien-tation of the transducer, is the wiring harness con-necting the transducer to the display unit. Eventhough these cables are generally much longer thanneeded for a typical installation, the cable lengthshould not be altered in any way. (Factory-suppliedextensions are available if more length is needed.) If

18"

Lifting Strake

Skeg

12"

3"–6"

Fig. 12-9. Transducer location, with separation zones measured out.

188


you find you have excess after running the cable toyour display, do not cut it and splice the connector tothe shortened harness! The length of this harness isengineered to a precise resistance, and alteration willaffect the performance of the unit. Coil excess wireneatly and lock it together with some tie wraps. Hidethe coil behind an out-of-the-way panel away fromany other electrical cables or harnesses. It’s possiblefor this cable to be affected by cross-induction fromother electrical cables and devices. (Remember, allwires with electricity running through them have amagnetic field around them.) Cross-inductancehere will affect the sensitivity of your depth-sounderor fish-finder.

Inside-the-Hull MountIf you aren’t using a transducer with a water-temper-ature probe built into it, you may want to mount yourtransducer inside the hull. This is the simplest of theinstallation choices and will generally prove satisfac-tory, but you may experience a loss of range. If yourboating keeps you in less than about 100 feet of wa-ter, this method may work well for you. This ap-proach only works on boats with a solid-fiberglassbottom. Cored bottoms will not precisely transferthe ultrasonic waves from the transducer, and per-formance may be greatly hindered. If you’re not sureif your boat bottom is cored, check with the builderbefore moving ahead on this type of installation.

If you’re determined to try for an in-hull installa-tion, do some experimenting first. Connect the trans-ducer to the sounder’s display and temporarilyadhere the face of the transducer to the inside of thehull with some nonhardening adhesive, such asBoatLIFE caulk or a similar polysulfide sealer. Try thesounder for a few days under all of the conditionsyou’re likely to encounter. If the display picture isclear and accurate, go for it! If not perfect, but stillfunctional, try different locations inside the hull.

Avoid areas of the hull where it inclines more thanabout 15 degrees. Mounting the transducer at any an-gle greater than this will send its wave pattern to theside of the boat, and not straight down to the bottom.

Once you find the best spot for the transducer,clean away the temporary adhesive and degrease the

hull with some acetone or alcohol. Lightly sandboth the face of the transducer and the hull withsome medium-grit (100-grit) sandpaper. Wipedown everything once more to clear the dust away.Next, apply enough fast-curing 3M 4200 poly-urethane adhesive to provide full contact with theentire face of the transducer. Push the transducerinto the adhesive and wiggle it slightly from side toside to break any air bubbles in the glue. Allow it tosit for about two hours to cure. 3M 4200 is muchbetter for this purpose than the 3M 5200; it curesmuch more quickly than the 5200 and is a bit lesstenacious, making for easier replacement of thetransducer when the time comes to do so. Figure12-10 illustrates a typical glued-in transducer.

Through-Hull MountThrough-hull mounting of a transducer gives excel-lent performance, provided the basic rules for lo-cating it are followed. In addition to the locationrequirements already noted, make sure the trans-ducer is positioned so that its face is aimed straightdown and not canted to one side or the other. If youwant to mount the transducer on an angled sectionof the hull, a mounting pad is required. Use an ap-propriate material for the fairing block (see below),and make sure the stem of the transducer is com-pletely sealed so that water can’t leak into the boat.It’s also important that water not come into contact

3M Brand4200 Adhesive

Fig. 12-10. Inside-the-hull mount with transducer glued inplace.

189


with the freshly exposed fiberglass or core materialaround the perimeter of the through-hull hole; aleak here exposes the laminate or core to water andcan damage the laminate as water attempts to mi-grate into it. 3M 4200 or 5200 works well for thispurpose.

As for the material to use for the fairing block,stay away from wood. Traditionally, wood has beenthe material of choice for this job, but today it’s un-necessary and less desirable than modern materialssuch as Delrin or Marelon. These miracle plastics arenow used for making seacocks and other through-hull fittings, and are widely used in other industries.They are available in sheet and block form from in-dustrial supply houses. The beauty of using plasticis that it will never rot, and it won’t crack on thegrain as do hardwood blocks. These plastics are easyto work using regular woodcutting and formingtools. Figure 12-11 illustrates a through-hull mount-ing with a fairing block.

Transom MountOn smaller boats, the transom mount is usually thesimplest and easiest of the three choices for trans-ducer installation. Figure 12-12 illustrates a typicalinstallation.

Virtually all fiberglass production boats built to-day use a plywood-cored transom. To prevent waterfrom migrating into the core, which will eventually

rot the wood, mounting screws and any holesdrilled for routing the transducer cable through thetransom must be sealed with 3M 5200 or a similarproduct. In addition, the mounting bracket must beset up so that the face of the transducer is pointingstraight down, as with the two other installation options.

Troubleshooting Fish-Finders and Depth-SoundersFor several reasons, fish-finders and depth-soundersare a bit more finicky than other types of electronicequipment. They are sensitive to voltage and willonly operate within a certain voltage range, typicallybetween 10.5 and 16.5 volts for a 12-volt unit. So,that all-night fishing trip at anchor could conceiv-ably drain your battery to below the minimum 10.5-volt level. A faulty voltage regulator on your boatcould also allow the upper 16.5-volt threshold to bereached. Depending on which depth-sounder orfish-finder you have, you might hear an alarm indi-cating high or low voltage, or the unit may automat-ically shut down. There is no problem with the unititself, but it’s a problem nonetheless.

The other fairly common problem with theseunits is fouling of the face of the transducer with seagrowth. Barnacles and other marine growth willeventually block the face of the transducer and affectits ability to transmit and receive a signal. The solu-

Rubber Washer

Hull

Plain Washer

DelrinMounting“Pad”

5200 Adhesive

Transducer

Fig. 12-11. Through-hull mounting of transducers with fair-ing blocks.

Fig. 12-12. A transom-mounted transducer.

190


tion here is simple: Either periodically wipe downthe face of the transducer with a wet cloth to clearthe surface, or prevent the fouling in the first placeby using transducer antifouling paint, available atWest Marine and other marine supply houses. Idon’t recommend that conventional bottom paintbe used to protect these surfaces.

If your fish-finder or depth-sounder stops work-ing altogether or begins to send mysterious signalsthrough your display, there are several additionalsteps you can take to isolate the problem. First, en-sure that the display unit is get-ting power and has a goodground, just as you would forany electrical appliance. Useyour multimeter, set up to readvolts, to make sure the voltageis not below your unit’s mini-mum threshold. If it is, deter-mine why by using all of themethods described throughoutthis book.

Checking your transducermay require hauling the boat soyou can get at the face of theunit. If you’re up to it, a briefunderwater swim may be allthat’s needed. With the sounderturned on, you should hear aticking noise coming from thetransducer as it attempts totransmit its signal. If you don’thear a ticking sound, the trans-ducer is faulty. Also, if you rubthe palm of your hand acrossthe face of the transducer whilesomeone watches the display,they should get a fuzzy readingacross the screen. If not, thetransducer is at fault and needsto be replaced. Naturally, youshould also become familiarwith the controls and calibra-tion settings for your fish-finderand depth-sounder and be surethey are set up properly.

Installing a GPS ReceiverWhether you’re installing a conventional GPS receiveror a chart plotter with an integrated GPS sensor, youessentially need to make the same considerations asyou would with all other electronic devices. One thingthat will make a minor difference in the installation ofyour GPS unit is whether or not you select a standardor differential GPS (DGPS) configuration.

Like all of the equipment discussed so far, the lo-cation for the display unit must be carefully consid-

DC +

DC -

Calibrated FactorySupplied Cable

May have achassisground

GPS Antenna

DC +

DC -

Fixed length cable


GPS Antenna

DC -

DC +

Fig. 12-13. Wiring layout for a standard GPS installation.

Fig. 12-14. Wiring layout for a differential GPS (DGPS) receiver.

191


ered. Follow the procedures described above for de-termining any compass deviation and getting powerto the receiver. The big consideration is where to lo-cate the GPS antenna. GPS receivers use receive-onlyantennas that need a clear view of the sky at all times.Even something like a Bimini top or a windscreencan affect the integrity of a GPS signal. Also, radiotransmissions from other electronic equipment suchas cell phones, VHF radios, and single-sideband(SSB) radios can affect a GPS signal.

The rules here are simple and not too hard tocomply with, even on small boats. Basically, the idealis to maintain about a 1-meter separation, or a littleless than a yard, between transmitting antennas andthe GPS receiving antenna. On most boats this issimply a matter of mounting the VHF antenna onone side of the bridge and the GPS antenna on theother. Mission accomplished! On boats with elabo-rate gear-mount brackets and airfoils, just keep frommounting these antennas adjacent to each other.

GPS is a line-of-sight system between the an-tenna and satellites orbiting overhead. The antennascans the sky via a conical pattern that pointsstraight up. So, unlike VHF, mounting an antennatoo high can actually be detrimental to its perfor-mance in a rolling, pitching sea, particularly if youhave selected the improved accuracy provided by adifferential receiver. An antenna mounted too highwill drive the GPS unit crazy as it swings back andforth trying to find its exact location. Low and asclose to the centerline of the boat as you can get isthe way to go with this installation. Any of the com-mercially available mounting brackets for these an-tennas will do just fine, but don’t think you’llimprove performance by using an extension pole,as you might with a VHF antenna.

If you have a differential GPS receiver (DGPS),one that also receives radio position data from land-based stations in addition to satellite signals, you mayneed an additional positive and negative wire to theantenna.

As with fish-finder and depth-sounder transducercables, your GPS antenna comes with a fixed-lengthcable for attachment to the display unit. Don’t alter

its length, and keep any extra cabling coiled awayfrom other cables and harnesses. Figure 12-13 onpage 190 illustrates a typical wiring hookup for a GPSwithout DGPS. Figure 12-14 on page 190 illustratesa typical installation with a DGPS receiver.

Installing Your Own RadarIn the old days, the average boatowner wouldn’t havedreamed of installing his or her own radar. Today,radar manufacturers have come a long way, and ownerinstallation is not only practical but not that difficult.

The big consideration with radar is the mount-ing of the antenna (scanner). Four basic rules must befollowed:

� Install the scanner on your cabintop or on an ap-

propriate mast with a platform designed to ac-

cept the mounting bolts.

� Position the scanner so that the antenna gets a

good all-around view with as few parts of the su-

perstructure or rigging as possible intercepting

the scanning beam. Any obstructions will cause

shadows and blind sectors on the radar screen.

� To minimize electrical interference, don’t route

the cabling from the antenna near any other on-

board electrical equipment or cabling, just as with

other gear mentioned above.

� Remember that a radar antenna creates pro-

nounced compass deviation. Keep a separation

zone of about 51⁄2 feet (1.7 m) between the radar

antenna and your compass.

When installing an antenna on a powerboat,consider the average angle at which your boatcruises while underway. If the antenna is mountedperfectly level with the boat at the dock, it will tendto aim at the stars while underway. Figure 12-15 il-lustrates the static angle for the antenna and the ef-fect this slightly downward mounting has on thebeam while the boat is underway. To determine theexact angle of the antenna to use, spend a morningdetermining the amount of lift your boat goesthrough from a standstill to cruising speed. Once

192


you have established this angle, you’ll know howmany degrees to tilt the forward edge of your radarantenna downward for optimum scanner perfor-mance while the boat is under way. Typically thisnumber is around 10 or 15 degrees.

The antenna has a definite front-facing positionthat must be observed. Follow the manufacturer’s in-stallation instructions if you’re not sure how toachieve this important orientation. Also, as with theother gear mentioned, the cable that comes with theradar is of a calibrated lengththat should only be alteredby installing a factory-sup-plied harness, which is avail-able in different lengths.

One last thing regardingthe radar antenna: All closed-array scanners (those with afiberglass enclosure) comewith a condensation drainvalve on the bottom shell ofthe antenna housing. Makesure this drain is unob-structed and working as itshould at all times. Conden-sation buildup inside the an-tenna housing will destroythe expensive circuitry inthere.

Once the antenna ismounted and the lead is fed

to the approximate location of the display, perma-nently mount the display. Again, ergonomics is im-portant. Radar is useless if you don’t have a clear,unobstructed view of the entire display. Connect thedisplay to the dedicated instrument bus for positiveand negative return, run a ground from the back ofthe chassis (at the wingnut and stud) to the nega-tive bus bar, connect the antenna cable to the appro-priate socket, and you’re ready to go! Figure 12-16illustrates the wiring hookups for a typical radar in-stallation, with some of the other mentioned con-cerns pointed out in the diagram.

I have one last general note regarding electronicequipment: Never attempt to use this gear untilyou’ve read through the fine points of the owner’smanual and documentation that comes with theequipment. In most cases, before the gear can be usedeffectively there is an initialization or preliminarytuning procedure that must be followed. Be familiarwith these steps, and make sure you take them beforeyou head off into the sunset. The equipment avail-able today is good, but it’s not completely magical; itneeds user intervention to give the best results.

10 - 15°

DC +

Scanner

DC -

Fixed lengthcable


DC -

DC +

Fig. 12-15. Static angle for powerboat radar antenna installation.

Fig. 12-16. Typical wiring hookup for a radar system.

193

ABYC—American Boat & Yacht Council, Inc. Thepreeminent standard-making organization forthe recreational boating industry. The ABYC’sStandards and Technical Information Reports forSmall Craft covers all areas of small-boat con-struction and repair, not just electrical matters.

alternating current (AC)—Current that reverses di-rection. In the United States, the current reversesdirection at the rate of 60 times per second, at 60cycles, or 60 Hz. In Europe and other parts of theworld, the standard is 50 Hz. See also direct cur-rent (DC); frequency; Hertz (Hz).

alternator—A machine that uses the principle ofmagnetic induction to produce electricity. Alter-nators produce AC, which must be rectified toDC to recharge onboard batteries.

ammeter—A meter used to measure the currentflowing through a circuit. Conventional metersmust be hooked up in series with the circuit.Modern inductive-style meters simply clamparound a wire in the circuit.

ampacity—The amount of amperage an electricalconductor or device can safely conduct.

ampere—The unit of measure for electrical current,or rate of electrical flow past a point in a circuit.One ampere is equal to one coulomb (6.24 � 10to the 18th power) of electrons passing a givenpoint per second. Amperage is the stuff that tripscircuit breakers and fuses, and, if not controlled,can burn up your boat!

amp-hour—A current of one amp flowing for onehour; a measure of the electrical energy stored ina battery.

anode—The more positively charged electrode in anelectrical cell.

average-responding multimeter—A meter whosevoltage and amperage readings are calculatedwith an averaging formula.

battery—An electrochemical device that producesvoltage, or a voltage differential across its terminals.

battery bank—A group of two or more batterieslinked together electrically.

battery combiner—Electronic, voltage-sensitiveswitching device for automatically combiningand separating batteries.

battery isolation switch—A mechanical switch usedto connect single or multiple batteries in parallelto a load.

battery isolator—An electronic device that usesheavy-duty diodes to block electrical flow in onedirection, effectively keeping batteries that arecombined separated from each other electricallyto prevent the discharge of one into the other.

battery reserve capacity—The number of minutes anew, fully charged battery at 80°F (26.7°C) canbe discharged at 25 amperes and maintain a volt-age of 1.75 volts or more per cell (10.5 volts for a12-volt battery).

blade-type (ATO) fuse—Common fuse type usinga colored plastic case for the fuse element; widelyused in automotive applications today.

branch circuit—A subcircuit fed from a main or pri-mary circuit.

bus bar—Metal bar used as a termination point formultiple conductors and circuits. A commonpoint for either grounding or positive power feed.

bus (AGC) fuse—The traditional glass cylinder styleof fuse.

cable—Wiring of any type; also cabling.

capacitive-discharge ignition (CDI) unit—The“brain” of a CD ignition system.

capacitor—An electronic component that stores anelectrical charge when voltage is applied.

Glossary


194

G L O S S A R Y

carbon tracking—The carbon path etched into plas-tic or other insulating material by high voltage.

cathode—The negatively charged electrode of a cell.See also anode.

cell—The smallest unit of a battery. A 12-volt stor-age battery has six cells.

charge coils—Coils within a CD ignition systemused to step up voltage supplied to the ignitioncoils.

chassis ground—The case ground for metallic-casedelectrical equipment.

circuit—A complete path for electrical flow from thepositive power source or terminal to the negativeor ground terminal. A complete circuit has thefollowing key elements: a power source, circuitprotection (most circuits), a switch, an electricalconductor, a load or an appliance, and a returnconductor to ground (negative).

circuit breaker—An automatic switch that “trips”when the rated current flow through it is ex-ceeded. A bimetallic circuit breaker uses the dif-ferential thermal expansion of dissimilar metalsto open the switch.

circular mils (CM)—Cross-sectional area of a con-ductor.

closed circuit—A complete circuit, one that isturned on.

coaxial cable—Used typically for antenna leads andto interconnect marine electronic equipment.This two-conductor cable consists of an innerconductor insulated by a dielectric shield that issurrounded by a braided wire conductor andthen insulated on the outside by another layer ofnonconductive sheathing.

cold-cranking amps (CCA)—The number of ampsa battery at 0°F (�17.8°C) can deliver for 30 sec-onds and maintain a voltage of 1.2 volts per cell ormore.

color coding—One of several acceptable methodsof identifying wiring in circuits.

conductor—Any material that has a minimal amountof resistance to electrical flow through it.

conduit—A pipe in which electrical wiring is routed.

continuity—A complete path or circuit that will al-low electrical current flow.

continuous rating—Rated for continuous exposureas compared to intermittent exposure.

corrosion—The process by which metals are de-stroyed. See also galvanic corrosion; stray-currentcorrosion.

crimp—(n.) A type of connector used for terminat-ing wire. As in captive, ring-eye, etc. (v.) To attacha crimp-type connector to a wire using an appro-priate crimping tool.

cross-induction—The inducement of electron flowin a conductor from the magnetic field surround-ing a nearby current-carrying conductor.

CRT—Cathode ray tube. Televisions and comput-ers—before they went to flat screens—used tohave CRTs.

current—The movement of electrons through a ma-terial.

cycles—In AC, the current shift from + to – andback to + is one cycle.

DC ground conductor—A normally current-carrying conductor connected to the side of thepower source that is intentionally maintained atboat ground potential.

DC grounding conductor—A normally non-current-carrying conductor used to connectmetallic non-current-carrying parts of direct-current devices to the engine negative terminal,or a bus attached directly to it. Its purpose is tohelp minimize what is known as stray-current cor-rosion and is also sometimes connected into alightning protection system as well. This wiring,which is generally covered with green insulationand connects to things like seacocks and propeller-shaft struts, should never be used as aDC ground return for an electrical appliance.

195

G L O S S A R Y

deep-cycle battery—A battery designed to withstandbeing deeply discharged at a moderate rate ofcurrent draw over an extended period.

de-rating—Reduction of a nominal rating, typicallyused with ampacity and voltage drop tables.

Deutsch plug—Trade name for a high-quality wa-terproof plug assembly.

DGPS—Differential global positioning system usingboth satellite and land-transmitted data to calcu-late position.

dielectric—An insulating material.

diode—An electrical semiconductor that allowselectrical flow through it in only one direction.

direct current (DC)—Electrical current that flowsin one direction. See also alternating current (AC).

double-pole—A classification of switch or circuitbreaker that allows for the opening of two sepa-rate connections simultaneously.

dry-cell battery—A battery using a dry, paste-likeelectrolyte instead of a liquid. See also wet-cellbattery.

DVOM—Common acronym for digital volt-ohmmeter, also known as a multimeter or VOM.

earth ground—A point that is at the same voltagepotential as the local earth.

electrical potential—Voltage.

electrolyte—The solution inside a battery, but canbe any electrically conductive fluid, such as saltwater.

engine negative terminal—A bolt or stud on an en-gine where the negative battery cable is connected.

ferro-resonant charger—Simple unit using a ferro-resonant transformer to convert AC to a lowervoltage before being converted to DC for charg-ing batteries.

field winding—The wire coils wound onto the ro-tor inside an alternator. When electrical currentflows through these windings an electromagneticfield is created around the rotor assembly, which

induces current flow in the alternator’s statorwindings as the rotor spins.

float charge—The third and final phase of batterycharging. Also known as the finish stage.

flywheel—A wheel used to maintain an engine’srolling inertia between firing strokes.

frequency—The number of complete alternationsper second of alternating current.

fuse—A conductive device designed to melt whenamperage flow through it exceeds a rated amount.

galvanic corrosion—Corrosion resulting from dissim-ilar, electrically connected metals being immersedin an electrolyte.

galvanic isolator—A device installed in series withthe green grounding conductor of the AC shore-power cable designed to block galvanic DC currentflow but permit the passage of AC if required.

galvanic potential—A reference to where a givenmetal may fall on a galvanic series of metals table.“Anodes” and “zincs,” as they are commonlycalled, have a higher galvanic potential thanMonel, stainless steel, and bronze.

gang plug—Plug assembly used for connecting mul-tiple conductors.

gapping—Adjusting the air gap between two elec-trodes.

gel-cell battery—Type of battery with the activeelectrolyte contained in a gelatinous medium.

generator—Generally, a machine that produceselectricity.

GPS—Global positioning system.

ground—At the potential of the Earth’s surface. Asurface or mass at the electrical potential of theEarth’s surface, established at this potential byan electrically conducting connection, either in-tentional or accidental, with the Earth, includingany metal area that forms part of the wetted sur-face of the boat’s hull.

196

G L O S S A R Y

ground-fault circuit interrupter (GFCI)—A deviceintended to protect people that functions to de-energize a circuit or a portion of a circuit when acurrent to ground exceeds a predetermined value(5 milliamps in the U.S.).

harness—A group of conductors running together.

heat-shrink tubing—Insulating sheath that shrinksto size when heated.

heat sink—A mounting for an electronic compo-nent designed to dissipate heat generated by thecomponent to the surrounding air.

Hertz (Hz)—The unit of frequency of an alternatingcurrent. One Hertz is equivalent to one cycle persecond.

horsepower—A measure of power. One horsepoweris equivalent to 746 watts.

hot—Generally considered the power feed conduc-tor in electrical circuitry.

house battery—Used to supply DC loads other thanthe engine stater motor.

hydrometer—A float-type device used to measurethe specific gravity of a fluid relative to another.In electrical work, the battery hydrometer is usedto measure the specific gravity of the battery elec-trolyte relative to pure water.

ignition protected—A critical designation for anyelectrical device that is to be used in an area wheregasoline, battery, or CNG or LPG vapors may ac-cumulate. The ABYC describes ignition protec-tion as: “the design and construction of a devicesuch that under design operating conditions: itwill not ignite a flammable hydrocarbon mixturesurrounding the device when an ignition sourcecauses an internal explosion, or it is capable of re-leasing sufficient electrical or thermal energy toignite a hydrocarbon mixture, or the source ofthe ignition is hermetically sealed.” It is impor-tant to note that unlike most of the ABYC stan-dards, ignition-protection requirements are alsomandated by USCG regulations, and complianceis not voluntary, but mandatory.

impedance—A form of resistance, the ratio of volt-age to current.

inductance—See cross-induction.

induction—See cross-induction.

inductive pickup—Used with measuring instru-ments to sense electrical current flow throughwires.

in-line (fuses, etc.)—A series connection.

insulator—Material with a high electrical resistance.

intercircuit short—Anywhere two circuits inadver-tently become connected.

intermittent rating—See continuous rating.

internal short—Short circuit within the case of anelectrical appliance.

inverter—A device that converts DC voltage to ACvoltage.

joule—A measurement of energy. One Joule equalsone watt for one second.

jumpers—Short lengths of conductors, either wireor strapping.

key—To activate.

kilo (k)—A common prefix meaning 10 to the thirdpower, or 1,000.

lead—A length of wire, usually fairly short. As in“meter lead.”

lead-acid battery—Typical battery using lead platesand sulfuric acid electrolyte.

LED outlet tester—Tester used to verify AC plugoutlet wiring connection status that uses light-emitting diodes (LEDs) to signal status of con-nections at the outlet and its connected wiring.

life cycles—The estimated number of times a batterycan be discharged to a specified level and broughtback up to full charge before it fails.

live—Meaning power is available.

load—Any device in a circuit that dissipates power.

lugs—Ashort,threadedstudusedforwiretermination.

197

G L O S S A R Y

magnetic circuit breaker—Breaker that uses themagnetic field generated by a current-carryingcoil to open the circuit.

magnetic field—Magnetic lines of flux, invisible butpresent around all conductors with electrical cur-rent flowing through them. The magnetic linesof flux surrounding the Earth are the basis for thefunction of a magnetic compass.

magnetic separation—Insulating or moving awayfrom excessive magnetism.

mega (M)—Prefix meaning 10 to the sixth power, orone million.

micro (�)—Prefix meaning 10 to the minus sixthpower, or one millionth.

milli (m)—Prefix meaning 10 to the minus thirdpower, or one thousandth. As in milliamp or mil-livolt.

multimeter—Electrical meter with multiple func-tionality.

ohm (�)—The unit of measurement of electrical re-sistance.

ohmmeter—A device that measures electrical resis-tance.

Ohm’s law—The mathematical equation that ex-plains the relationship between volts, amps, andohms.

open—See open circuit.

overcharging—Forcing excessive current into a bat-tery. Overcharging causes excessive batterygassing and loss of electrolyte, a dangerous situa-tion in either event.

open circuit—A break in a circuit that interrupts theflow of current.

open-circuit voltage—The voltage reading acrossthe terminals of a battery at rest, with no chargegoing in and nothing drawing power from it.

overcurrent-protection device—A fuse, circuitbreaker, or other device installed in a circuit andintended to interrupt the circuit when the currentflow exceeds design ratings.

overrating—Applying more voltage or amperage toa device or component than it was designed totake.

panelboard—Electrical distribution panel. Includesbranch circuit breakers or fuses, and both nega-tive and positive bus bars. May also contain sys-tem volt and amp meters and in the case of ACpanels, a reverse-polarity indicator.

parallel circuit—A circuit that allows more than onepath for current to flow.

pie formula—P � I = E, or W = V � A

pinging—Knocking noise from engine that soundslike marbles are bouncing inside.

polarity—The distinction between + and – in a circuitor on a load device.

potential—See electrical potential.

power—The rate at which energy is used or con-verted. The unit of measurement is the watt,which equals amperage times the voltage. Onehorsepower equals 746 watts. See also horsepower.

pulsar coils—See trigger coils.

radome—See scanner.

reference voltage—The open-circuit voltage of apower source.

relay—An electromechanical switch. See also sole-noid.

reserve capacity—The time in minutes that a batterycan deliver 25 amps before dying.

resistance—Measured in ohms. The opposition toelectrical current flow (amps).

reverse polarity—Connecting battery cables back-wards. Or, in AC, the reversal of the black andwhite conductors.

RFI—Radio frequency interference, emitted by elec-trical devices. Can produce radio “noise,” andcan cause navigation equipment to malfunction.

ripple voltage—Small amount of AC voltage thattypically leaks past rectifiers inside alternators.

198

G L O S S A R Y

root-mean-square (RMS) multimeter—One usingpeak AC voltage values to calculate its readings.

rotor—The moving component inside an alternatorthat has the field winding wrapped around it.

rpm—Revolutions per minute.

scanner—Moving radar antenna (rotating).

self-discharge—The gradual loss of a battery’s ca-pacity as it sits in storage.

self-limiting—An electrical power source whosemaximum output is restricted by its magneticand electrical characteristics.

self-scaling (auto-ranging) ammeter—A meter thatautomatically selects its best range for a measure-ment.

series circuit—A circuit having only one path forcurrent to flow through.

series-parallel circuit—A circuit combining ele-ments of both a series and parallel circuit.

sheath—A material used as an insulating protectivecover for electrical wiring.

shore power—Power delivered from the dock.

short circuit—A circuit fault that effectively short-ens the designed path of current flow through acircuit. Short circuits usually eliminate the loadfrom the circuit, allowing excessive current toflow.

shunt—A short electrical bypass, generally associ-ated with an ammeter.

single loads—An individual electrical load in a circuit, as compared to multiple loads suppliedby a circuit.

sine wave—The waveform made when alternatingcurrent is charted over time.

slave relay—See solenoid.

slow-blow (MDL) fuse—A fuse with a delayed ac-tion used in motor circuits and other circuitswhere start-up load is significantly greater thanthe continuous current draw on the circuit.

smart charger—Computerized multistage batterycharger.

socket—The female part of a plug and socket con-nector.

solenoid—An extra-heavy-duty relay. Used forswitching high-current-draw circuits such asstarter-motor circuits.

specific gravity—The density of a fluid. In electricalterms, the density of battery electrolyte as com-pared to pure water. Indicates state of charge ina battery cell.

spike—Sudden surge in voltage.

starting battery—Cranking battery capable of deliv-ering high amperage for brief periods.

static charge—Surface charge on a battery. Highvoltage but no amperage to back it up.

stator—The stationary armature on an alternatorthat the rotor spins inside of, where alternatorcurrent is produced.

stray-current corrosion—Corrosive activity inducedby electrical leakage. See corrosion.

sulfation—The normal chemical transformation ofbattery plates when a battery discharges. If leftunattended, the sulfate turns to a crystallinesubstance and attaches itself permanently to thebattery plates, ultimately ruining the battery asless and less plate area is exposed to the sur-rounding electrolyte solution.

surface charge—See static charge.

surge (spike)—See spike.

switch—A device used to open and close a circuit.

tachometer—Revolution counter.

terminal—A point of connection to any electri-cal device. As in battery clamp, ring eye con-nector, etc.

tilt switch—Mercury switch designed to turn off thestarting circuit on an outboard engine when it’stilted up out of the water.

timing—Engine’s ignition timing. Point at whichthe spark plug fires in a cylinder.

transducer—Two-way sender-receiver used withdepth-sounder.

199

G L O S S A R Y

transformer—An electrical device consisting of twoor more coils used to magnetically couple one cir-cuit or section of a circuit to another. Transform-ers come in three basic configurations:one-to-one, where voltage on both sides of thetransformer (primary and secondary) stays thesame; step-up, where the voltage is increasedfrom the primary to the secondary side of theunit; and step-down, where the opposite occurs.

trigger coils—Used to send an electrical charge to aCDI’s control box to tell it which cylinder to firenext.

trim gauge—Used to indicate relative IO drive oroutboard engine trim angle.

trip (breaker)—To open the circuit.

trip-free circuit breaker—A breaker designed insuch a way that the resetting means cannot bemanually held in to override the current-interrupting mechanism.

underrating—Not having adequate ampacity. Seealso ampacity.

ungrounded conductor—A current-carrying con-ductor that is insulated from ground. Oftenthought of as the “hot” wire in a circuit.

volt—The unit of voltage or potential differencefrom one side of a circuit to another.

voltage drop—The loss of voltage as it works its waythrough a circuit. Excessive voltage drop indi-cates unwanted resistance in a circuit or circuitcomponent.

voltage regulation—Maintenance of voltage outputdespite variation in output current within engi-neered parameters.

watt—A unit of power. The English unit of mea-surement is the horsepower, which equals 550foot-pounds per second or 746 watts.

waveform—Voltage as a function of time of a re-curring signal. The waveform of AC voltage is thesinusoid, much like that of an ocean wave.

wet-cell battery—A typical cranking or deep-cyclebattery, as compared to a dry-cell flashlight bat-tery. Wet-cell batteries can be recharged; mostdry-cells cannot.

200

Resources

A number of products and tools are mentionedthroughout the Powerboater’s Guide to Electrical Sys-tems. In most cases your local marine store or chan-dlery has or can get you the equipment we’vediscussed. Here are some other useful resources:

Blue Sea SystemsA great resource for parts as well as technical advice.Call 1-800-222-7617 for customer service, or 360-738-8230 for the technical support line; or go towww.bluesea.com.

Boat/U.S.Check them out at www.boatus.com or call 703-461-4666.

Boater’s WorldCall 1-877-690-0004 or visit their website atwww.boatersworld.com.

Defender IndustriesCall 1-800-628-8225 or go to www.defender.com.

MAC Tools Corp.MAC distributes through local franchised mobilevendors. To find a dealer near you, go to www.mactools.com or call 1-800-622-8665.

NAPA Auto Parts StoresNAPA has an excellent line of marine parts and me-chanic’s tools. You can find the stores nearest youat www.napaonline.com.

Snap-OnIn my view, Snap-On produces the finest tools for themechanic available anywhere in the world. If you arelooking for the best, check out www.snapon.com.Like MAC, Snap-On distributes through local mo-bile vendors, but the distribution network is world-wide.

West MarineCall 1-800-685-4838 or go to www.westmarine.com.


www.mactools.com

www.mactools.com

www.napaonline.com

www.bluesea.com

www.boatus.com

www.snapon.com

www.boatersworld.com

www.defender.com

www.westmarine.com

201

Numbers in bold refer to pageswith illustrations

Aabnormal instrument readings,

148–49abrasion protection, 58, 59absorbed-glass-mat (AGM) bat-

teries, 67–69, 97acceleration spark advance, 106,

110acceptance/absorption phase, 98accessories. See direct current

(DC) accessoriesAdvanced Marine Electrics and

Electronics Troubleshooting(Sherman), 155

AGC fuses, 48, 49alternating current (AC)

need analysis, for inverterselection, 171–73

overcurrent protection,162–63, 164, 165, 174

ripple-voltage test, 93–94safety, 157–58terminology, 156–57

alternating current (AC) appli-ances, 171, 172, 173

alternating current (AC) circuitbreakers, 162–63, 164, 165

GFCIs, 166–67alternating current (AC) cir-

cuits, 156–57on boats, 157checking, 167–70color coding for wiring,

158–59compared to DC circuits,

159–62marine vs. residential materi-

als, 162outlet connections, 164, 165overcurrent protection,

162–63, 164, 165, 174

panel feed wire, 162probe pen, 11safety with, 157–58shore-power wiring diagram,

159, 160wire size, 160–61, 162wiring bundles, 161

alternating current (AC) equip-ment. See also alternators

DC-to-AC inverter selection,170–75

galvanic isolators, 177–79generators, 172, 175–77, 176testing resistive, 170

alternators, 86–87engine-driven marine, 87marine vs. automotive, 88one-wire, 81problems with, 87–99tachometer failure and, 152testing, 91–94

American Boat & Yacht Council(ABYC)

amperage for conductors, 46,48, 161, 163

basic wiring standards, 41–46battery cables standards, 77battery location standards,

73–74battery switch standards, 19certification program, 158color code standards, 15–17development of standards,

40–41fuses and circuit breakers

standards, 46–51galvanic isolator standards,

178–79ignition protection, 52–53soldering terminals, 60temperature ratings standards,

46, 47, 48, 161, 162, 163voltage drop and wire size

standards, 32, 43, 44, 45, 137

wire and circuit protectionstandards, 40–59

wiring and connectionrepairs standards, 59–60

American Wire Gauge (AWG),41–42, 77

ammeters, inductive, 11, 29–30,36–37, 93, 169

amperage, 6–9AC, checking, 169adequate, 27–28allowable for conductors, 46,

48, 161, 163charging test, 93DC accessory requirements,

136DC equipment draws, 37measuring, 34, 36–37rating for ATO fuses, 49, 50testing, 42–43

Ampere, Andre-Marie, 6ampere-hours (amp-hours),

70–71, 171–73ampere-interrupting capacity

(AIC), 51amperes (amps), 5, 6, 7–8, 19,

71–72analog multimeters, 26Ancor

inductive ammeter, 11, 29multimeter, 29–30ratcheting crimper, 11, 61,

62, 143anode, 65, 156antenna gain, 184, 185antennas

GPS, 191radar, 191–92VHF, 184–85, 191

appliances, 2AC, 171, 172, 173DC, 8, 136–46

ATO fuses, 48, 49–50automatic float switch, 142

Index


automotive alternators, 88automotive batteries, 66average-responding multime-

ters, 26

Bbase timing, 110batteries. See also battery instal-

lationamp-hour ratings, 70–71basics of, 65–66CCA and MCA, 71–72cost comparisons, 68–69cycles, 66, 68–69dimensions, 71group sizes, 71maintenance and testing,

74–76, 75safety, 72–74selecting, 69–72sulfated, 66–67testing, 74–76, 82–8520-hour rating, 71types of, 66–70

battery-bank size determination,inverter, 171–73

battery boxes, 73, 74battery cable ends, soldering, 60battery cables, 77, 131battery carrying strap, 72, 73battery chargers

ferro-resonant, 67, 96–97four-step, 96growth in demand for, 157smart, 96, 97–99testing, 89–94, 99

battery-charging phases, 97–98battery-charging systems. See

also alternatorsoutboard-engine, 94–96, 95shore-power, 96–99solar cells, 99symptoms, 89testing, 91–94

battery combiners, 77, 82battery hydrometer, 83–84battery installation

acceptable possibilities for,73–74

battery cables, 77battery combiners, 77, 82battery isolators, 77, 79–82battery switches, 77–79, 81series and parallel connec-

tions, 76–77battery isolators, 77, 79–82battery life, 68battery location, 73–74battery safety, 72–74battery switches, 19, 20, 77–79,

81belt tension and replacement,

89–90bilge blower

amperage draw, 43circuit for, 19, 20, 21wiring diagram, 21

bilge pumpinstallation, 140–44, 141, 142,

143wiring diagram, 143

bimetallic circuit breakers, 51blade-type fuses (ATO), 48,

49–50“blinking out” of electronic gear,

82blocking diodes, 99Blue Sea Systems, 82bridge rectifiers, 86–87bulkheads, abrasion protection

through, 58, 59bulk phase, 97–98bullet-type connectors, 145bus-type fuses (AGC), 48, 49butt connectors, 63, 64

Ccabin lights

circuit diagram, 32installation, 139–40wiring diagram, 140

cable, coaxial, 184–86cables, battery, 77, 131cables, vs. wires, 77calories, 6capacitive-discharge ignition

(CDI) systems, 104, 105,110–12

capacitive-discharge ignition(CDI) unit, 100–101, 104,110, 111, 112, 118, 121, 122,134

carbon tracking, 107–8cathode, 65, 156CD players

installing, 144–46wiring diagram, 146

Centerpin PL-259-CP coaxialconnectors, 186

charge coils, 104, 111, 115,116–18, 117

charge controller, 99charging amperage test, 93chassis ground circuits, 3circuit breakers, 2, 50–51

AC, 162–63, 164, 165ampere-interrupting capac-

ity, 51bimetallic, 51for DC accessories, 137–38engine-mounted, 91GFCIs, 166–67locations for, 55, 57magnetic, 51100–150 percent rule, 54–55,

56removing, 51–527–40–72 rule, 57, 58standards for, 46–51testing, 53, 54trip-free, 51, 162

circuit identification, 17–19circuit problems, 9–10circuit protection

in battery installations, 57, 58100–150 percent rule, 54–55,

567–40–72 rule, 57standards, 54–55, 57, 58

circuit protectors, 2circuits, 1–5. See also alternating

current (AC) circuits; directcurrent (DC) circuits;starter-motor circuits

chasing/finding, 19–20components of, 14–15, 20–22continuity/resistance tests, 39

202

I N D E X

identification of, 17–19marine, 2–3marine vs. automotive, 3motor, 54–55nonmotor, 55parallel, 2, 4problems, 9–10series, 2, 3–4series-parallel, 2, 4–5voltage drop, 8–9tachometer, 150

closed switch, 2coaxial (coax) cable, 184–86Code of Federal Regulations

(CFR), 102cold-cranking amps (CCA), 19,

71–72color coding

ABYC, 15–17for AC wiring, 158–59for DC accessories, 138ISO, 159reverse polarity, 159substituting wire colors,

18–19colored heat-shrink tubing, 18, 19colored tape and wire ties, 18compass deviation, 180–81, 191conductors, 2

allowable amperage of, 46,48, 161, 163

bundling of AC, 160–61insulation and temperature

ratings, 46, 47, 48, 161, 162,163

sizes for voltage drop, 43, 44,45

connection repairs, 59–64connectors, 60, 61

bullet-type, 145butt, 63, 64coaxial cable, 185–86

continuity, 37alarm, on multimeters, 27checking, 132–33, 150–51,

169–70measuring, 37–39trigger-coil and short-to-

ground tests, 117

corrosionof battery terminals, 75of cables and connections, 20,

75of fuses, 142galvanic, 177protection for ignition sys-

tems, 104, 106silicone sealers and, 109stray-current, 177–78

cranking batteries, 69–70, 82crimping, 61–63crimping tools, 11, 61, 62, 63cross-induction, 161–62, 188cruisers, batteries for, 70–72current-draw test, 127–28current requirements for starter

motors, 127

DDC-to-AC inverters. See invert-

ersdecibels (dB), 184, 185deep-cycle batteries, 67, 68,

69–70, 82depth-finders

installing, 186–90, 187, 188,189

troubleshooting, 189–90de-rating, 160detonation. See pingingDeutsch plugs, 104, 106diesel engines

amperage requirements,71–72

current-draw test, 127engine shutoff, 85oil-pressure sender failures,

152tachometer for, 150

differential GPS (DGPS), 190–91digital multimeters, 26–28, 38diode rectifiers, 95, 96diodes, 27, 79, 80, 82, 86, 99direct current (DC)

galvanic isolators and, 178inverter-chargers and, 96rectifiers and, 86–87, 95, 96

direct current (DC) accessoriesamperage requirements, 136color coding, 138fuses and circuit breakers,

137–38installing, 136–46length of wire, 137panel feed wire, 138voltage drop and wire size, 137voltage requirements, 136wire type, 137wiring diagram, 138

direct current (DC) circuitsamperage draws for onboard

equipment, 37compared to AC circuits,

159–62distribution panels, 52, 55, 56,

137, 160, 182, 183. See alsomaster distribution panels

distributor caps, 101maintenance of, 107–8

distributorless ignition systems(DIS), 102–3

distributors, 101–2double-pole AC circuit breakers,

163, 164draw test, 94dual battery installation, 57, 58,

79, 81DVA adapter, 115, 116–18, 117

EEd Sherman wiggle test, 169, 170electrical circuits. See circuitselectrical potential, 6electrical symbols, 13electricity, 1electrolyte, 65, 72–73, 83–84, 97electronic equipment

heat sinks, 144installing, 180–92

electronic ignition systems. Seeignition systems

end strippers, 11, 62, 143engine ground, 91, 128–29engine ignition switch, 133–35,

134

203

I N D E X

engine instrumentationabnormal readings, 148–49future equipment, 155interpretation problems,

147–48troubleshooting, 149–55

engine-mounted circuit break-ers, 91

engines. See diesel engines; igni-tion entries; outboard entries;starter motor entries

engine stop control, 112equalization phase, 96, 98extension harness, 132–33

Fferro-resonant battery chargers,

96–97field-excitation voltage testing,

92, 93field windings, 86fires, 78fish-finders

installing, 186–90, 187, 188,189

troubleshooting, 189–90float/final phase, 98Fluke RMS multimeters, 11, 30flywheel, 104, 116, 118, 121four-step chargers, 96frequency, 156fuel gauges

problems, 149, 152troubleshooting, 153–54wiring diagram, 153

fuel-tank sending unit, 153–54fuses, 2, 47–48

AGC, 48, 49ATO, 48, 49–50circuit breakers and, 50–51corrosion, 142locations for, 55, 57MDL, 48, 49, 141, 174100–150 percent rule, 54–55,

56ratings, 487–40–72 rule, 57, 58sizing, 137–38

standards for, 46–51testing, 53, 114

Ggain, antenna, 184, 185galvanic corrosion, 177galvanic isolators, 177–79galvanic potential, 66gasoline engines. See ignition

entries; outboard entries;starter motor entries

gasoline engines, CCA ratingsfor, 71, 72

gassing, 67gauges

abnormal readings, 149console-mounted voltmeters,

149, 152, 153fuel, 149, 152, 153–54future equipment and, 155mechanical, 147oil-pressure, 148, 152, 153,

154, 155temperature, 148–49, 152–53trim, 149, 154

gel-cell batteries, 67, 68–69, 97General Motors V8 engine, 154,

155generators, AC, 172, 175–77, 176GPS (global positioning system)

receivers, 181, 190–91grid, of battery, 66ground, 1

engine, 91shorts to, 9–10

ground continuity, 127grounded conductors, 158, 159grounded lead, 156, 159ground-fault circuit interruptors

(GFCIs), 158, 166–67grounding lead, 159, 187grounding lug, 187Guest, 78, 178

Hharnesses. See wiring harnessesHeart Interface Link 1000, 174,

175

heat-shrink tubing, 18, 64, 168heat-shrink-type crimp connec-

tors, 141heat sinks, 80, 144horsepower, 6hot lead, 156, 159hot-water heaters, 168, 170house battery, 69hydrometers, 83–84

Iidle-speed spark control, 110ignition coils, 101, 104, 105,

111, 115–16ignition-control module,

100–101, 102, 104, 110, 111,134

ignition problem quick-checklist, 114–20, 121

ignition protection, 52–53, 103,123, 166

ignition sensors, 108–9ignition switch, 133–35, 134ignition systems

final checks and ignition tim-ing, 120–22, 121

ignition problem quick-checklist, 114–20, 121

inboard components,100–103, 101, 102

maintenance of, 103, 104–7,106

MerCruiser Thunderbolt sys-tems, 107–10, 108, 109

outboard and PWC, 103–4,105, 110–20, 121

regulations regarding, 103testing, 112–20, 121troubleshooting, 106–7

ignition timing, 109–10, 122CDI unit, 111and engine problems, 106, 107

ignition wires, 103impedance, 26, 157inboard ignition-system compo-

nents, 100–103, 101, 102induction, 29, 87, 101, 103–4,

111–12, 156

204

I N D E X

inductive ammeters, 11, 29–30,36–37, 93, 169

inductive pickups, 28, 29, 36–37inductive voltage sensor, 167inside-the-hull transducer

mount, 188installations

battery, 76–82bilge pump, 140–44, 141,

142, 143cabin lights, 139–40DC accessories, 136–46depth-sounders, 186–90, 187,

188, 189DGPS receiver, 190–91dual battery, 57, 58, 79, 81electronic equipment, 180–92fish-finders, 186–90, 187,

188, 189galvanic isolators, 179GPS receiver, 190–91inverter, 173–74magnetic-field issue and,

180–81radar, 191–92RFI and, 181–82speakers, 145–46VHF radio, 183–86, 191zone of magnetic separation

and, 145, 181, 182instrumentation, engine

abnormal readings, 148–49future equipment, 155interpretation problems,

147–48troubleshooting, 149–55

insulationflexible cords, 46wire, 43, 46wiring conductors, 46, 47, 48,

161, 162, 163intercircuit shorts, 10, 106internal shorts, 10International Standards Organi-

zation (ISO) color coding,159

inverter battery-bank sizing,171–73

inverter-chargers, 96

inverters, 170AC need analysis, 171–73installing, 173–74monitoring, 174, 175waveform, 175

JJoule, James, 6joules, 5, 6jumper leads, 11jumpers, 108junction boxes, 20–22

Kknock-retard spark control,

109–10

Llabels, for circuits, 17–18lead (wire), 3lead-acid batteries. See batterieslight emitting diode (LED)

charging system testers, 93,94

light emitting diode (LED) out-let testers, 11, 167

lights. See cabin lightsloaded voltage, 92loads, 2, 92load test, 84–85Loctite, 108, 109Loran, 181, 182, 183lugs, vs. terminals, 77

Mmagnetic circuit breakers, 51magnetic-field issue, 180–81magnetic induction. See induc-

tionmagnetic separation, zone of,

145, 181, 182Marinco, 78, 169marine-cranking amps (MCA),

71–72marine vs. automotive circuits, 3marine vs. residential AC mate-

rials, 162

master distribution panels,14–15, 19–20, 142. See alsodistribution panels

MDL fuses, 48, 49, 141, 174mean best timing (MBT), 110mechanical gauges, 147Mercury Marine

ABYC color coding and, 17alternators, 81, 88, 89DIS, 102DVA adapter, 116–18, 117ignition sensor, 109SmartCraft, 155starter-motor circuit, 124,

125Thunderbolt systems,

107–10, 108, 109tilt-stop switch testing, 120,

121meter leads, 34, 36, 37modified-square waveform, 175motor circuits, 54–55multimeters, 5, 11, 25

analog, 26checking AC voltage at an

outlet, 168charging amperage test, 93checking generator voltage

and frequency, 176checking starter-motor cir-

cuits, 128–30, 129digital, 26–28, 38draw test, 94inductive pickups, 28, 29,

36–37measuring amperage, 34,

36–37measuring resistance and

continuity, 37–39, 150–51,169–70

measuring voltage, 30–31, 32,33

measuring voltage drop,31–34, 35, 130–32

multiple, 28–29open-circuit voltage test, 84outboard-engine tests,

115–20, 121recommended, 29–30

205

I N D E X

multimeters (continued)ripple-voltage test, 94selecting, 25–30testing neutral-safety switch,

132–33testing solenoids, 126, 127

NNational Electric Code (NEC),

17National Fire Protection Associ-

ation (NFPA), 17National Marine Manufacturers

Association (NMMA), 40neutral-safety switch, 128, 129,

130, 132–33no-load voltage, 92no-maintenance batteries, 68nonmotor circuits, 55

OOhm, Georg Simon, 5ohmmeters. See also multimeters

checking internal battery of,38

interpreting, 38–39testing spark-plug wire, 115

ohms, 5, 6, 7–8Ohm’s law, 5–8, 7oil-pressure gauges

problems, 148troubleshooting, 152, 154,

155wiring diagram, 153

oil-pressure sending unit, 152,154, 155

OMCalternators, 81, 88, 89starter-motor circuit, 124

100–150 percent rule, 54–55, 56open circuits, 9open-circuit voltage test, 84optical-timing systems, 122oscilloscopes, 157outboard and PWC ignition sys-

tems, 103–4, 105CDI system, 110–12engine stop control, 112

testing, 112–20, 121outboard-engine charging sys-

tems, 94–96, 95Outboard Engines: Maintenance,

Troubleshooting, and Repair(Sherman), 135, 148

outboard-engine starter circuits.See starter-motor circuits

outletsAC connections, 164, 165checking voltage at, 167, 168GFCI, 166–67

overcharging batteries, 76, 86,89, 97

overcurrent protectionAC, 162–63, 164, 165, 174standards, 57, 58

overload (OL) readings, 38–39,170

Ppanelboards. See distribution

panelspanel feed wire, 138, 162parallel circuits, 2, 4personal watercraft (PWC) and

outboard ignition systems,103–4, 105

CDI system, 110–12engine stop control, 112testing, 112–20, 121

pie formula, 6, 7, 8pinging, 106, 109–10PL-259 coax connectors, 185–86polarity, 156, 159

checking on AC circuits,167–70

polarity-sensitive electronicequipment, 181

potential, 5power formula, 7, 8power supply circuit, 20power supply for electronic

equipment, 182–83probe pen, for AC, 11ProMariner galvanic isolator,

178, 179pulsar coils, 104, 111

Rradar installation, 191–92radio-frequency interference

(RFI), 181–82radios. See single-sideband

radios; transistor radios;VHF (very high frequency)radios

ratcheting crimper, 11, 61, 62,63, 143

rectifiersbridge, 86–87diode, 95, 96silicon-controlled, 104

reference voltage, 92remote control

engine ignition switch and,133–35, 134

neutral-safety switch, 128,129, 130, 132–33

outboard-engine starter cir-cuit, 128, 129

outboard-engine stop switch,119–20

repairsprocedures, 40–59wiring and connections,

59–64resistance, 6–9, 156

measuring, 37–39resistive equipment checks, AC,

170resistor-type wiring, 115reverse polarity, 159ripple-voltage test, 93–94Romex wire, 41, 162, 164root-mean-square (RMS) multi-

meters, 11, 26, 30, 157rotor, 86, 108, 109

Ssafety

AC, 157–58AC generator, 176battery, 72–74, 84corrosion protection for igni-

tion systems, 104, 106galvanic isolators, 177–78

206

I N D E X

ignition protection, 52–53,103, 123, 166

overcurrent protection, 57,58, 162–63, 164, 165, 174

wire and circuit protectionstandards, 40–59

safety goggles, 84schematic diagrams. See wiring

diagramssensor coils, 104, 111series circuits, 2, 3–4series-parallel circuits, 2, 4–57–40–72 rule, 57, 58Sherman, Ed, wiggle test, 169, 170shore-power battery-charging

systems, 96–99short circuits, 9–10, 39shorts to ground, 9–10, 106, 117shunt meters, 28silicon-controlled rectifier

(SCR), 104silicone sealers, 109sine waveform, 175single-pole AC circuit breakers,

163, 164, 165single-sideband (SSB) radios,

182, 191slave relays, 125slow-blow fuses (MDL or T), 48,

49, 141, 174smart chargers, 96, 97–99Snap-On

amp gauges, 28, 29inductive ammeter, 11inductive meters, 128spark tester, 11, 113

Society of Automotive Engineers(SAE), 41–42, 52

solar cells, 99soldering

battery cable ends, 60terminals, 59–64

solenoidsoutboard-engine, 134–35starter, 125–28, 126, 127

spark, testing for, 112–13spark advance, 106, 110spark control, 109–10spark-plug gapping tool, 112

spark plugs, 103, 106, 112checking, 106, 107testing, 113–14

spark-plug wires, 115spark testers, 11, 113speakers, installing, 145–46specific gravity, 83–84sponge lead, 65standards. See under American

Boat & Yacht Council(ABYC)

Standards and Technical Infor-mation Reports for SmallCraft (ABYC), 32, 41

starter-motor circuits, 124, 125diagnostics, 124–25engine ignition switch,

133–35, 134neutral-safety switch, 128,

129, 130, 132–33outboard-engine, 128–32,

129, 130, 131troubleshooting, 125–28, 126,

127starter motors

current requirements for,127–28

diagnostics, 124–25, 135U.S. Coast Guard regulations

for, 123starter-motor solenoids, 125–28,

126, 127, 134–35starting battery, 69state of charge, 84static charge, 83stator windings, 86stop switch testing, 115, 119–20,

121stray-current corrosion, 177–78sulfated batteries, 66–67surface charge, 85switches

automatic float, 142battery, 19, 20, 77–79, 81closed, 2engine ignition, 133–35, 134neutral-safety, 128, 129, 130,

132–33stop, 115, 119–20, 121

switch panelsbilge pump, 142checking source voltage, 34master distribution, 14–15,

19–20, 142symbols, wiring diagram, 13–14

Ttachometers, 149, 150–52tape and wire ties, 18, 59, 60temperature compensation,

98temperature gauges

problems, 148–49troubleshooting, 152–53wiring diagram, 153

temperature ratings of wire, 46,47, 48, 161, 162, 163

temperature-sending unit, 153terminals

color codes for, 61integrity, 75soldering, 59–64

testing/tests. See also trouble-shooting

AC amperage, 169AC circuits, 167–70AC resistive equipment, 170alternator, 91–94amperage, 42–43, 93batteries, 74–76, 82–85battery chargers, 89–94, 99battery-charging systems,

91–94battery isolators, 80–81CDI units, 118charge coils, 115, 116–18, 117charging amperage, 93circuit breakers, 53, 54compass deviation, 181continuity/resistance, 39,

132–33, 150–51, 169–70current-draw, 127–28diodes, 27draw, 94fuel tank sender, 154fuses, 53, 114galvanic isolators, 179GFCI outlets, 166–67

207

I N D E X

testing/tests (continued)high-tension ignition coils,

115–16load, 84–85neutral-safety switch, 132–33ohmmeter battery, 38open-circuit voltage, 84outboard and PWC ignition,

112–20, 121polarity, 159, 167–70rectifiers, 96reverse polarity, 159ripple-voltage, 93–94spark, 112–13spark plugs, 113–14spark-plug wires, 115specific gravity, 83–84starter solenoid, 126–27stop switch, 115, 119–20, 121temperature-sending unit,

153three-minute charge, 85three-step voltage, 92–93tilt-stop switch, 115, 120, 121trigger coils, 115, 116–18, 117unregulated charging sys-

tems, 95–96voltage, AC, 167–69voltage drop, 31–34, 35, 128,

130–32water spray, 115, 116wiggle, 169, 170

3M 4200, 188, 1893M 5200, 188, 189three-minute charge test, 85three-step chargers. See smart

chargersthree-step voltage test, 92–93through-hull transducer mount,

188–89tie-wraps and clamps, 18, 59, 60tilt-stop switch testing, 115, 120,

121timing, 110. See also ignition

timingtools, 10, 11. See also specific tools

for bilge-pump installation,143

top dead center (TDC), 102

transducers, 187–90transformers, 101transistor radios, for checking

RFI, 182transom transducer mount, 189trigger coils, 104, 111, 115,

116–18, 117trim gauges, 149, 154trip-free circuit breakers, 51, 162troubleshooting. See also test-

ing/testsAC generators, 177depth-sounders, 189–90engine instrumentation,

149–55engines, 106–7fish-finders, 189–90ignition systems, 106–7starter-motor circuits,

125–28, 126, 127tachometers, 149, 150–52temperature, fuel, and oil-

pressure gauges, 152–55transducers, 187–90

T-type fuses, 48, 49, 141, 17420-hour rating, 71

Uundercharging batteries, 76, 86,

89Underwriters Laboratories (UL),

8, 52, 160ungrounded conductors, 158U.S. Coast Guard regulations,

40, 102, 123US Marine, 88, 89

VVHF (very high frequency)

radioscompass deviation and,

180–81installation, 183–86, 191power supply, 182

Volta, Alessandro, 5voltage, 6–9

checking on AC circuits,167–69

DC accessory requirements,136

loaded, 92measuring, 30–31, 32, 33no-load, 92open-circuit test, 84to outboard-engine solenoid,

134–35reference, 92ripple-voltage test, 93–94to starter-motor circuits,

128–30, 129to starter-motor solenoid, 127three-step voltage test, 92–93

voltage drop, 3, 8–9acceptable, 32AC vs. DC, 157, 160battery combiners and, 82conductor sizes for, 43, 44, 45for DC accessories, 137inverters and, 173–74maximum, 32measuring, 31–34, 35, 128,

130–32and wire size, 43, 44, 45, 137,

144voltage regulators, 87voltmeters. See also multimeters

to check outboard-enginestarter-motor circuit,128–29

for open-circuit voltage test,84

voltmeters, console-mounted,149, 152, 153

volts, 5, 6, 7–8Volvo Penta

alternators, 88, 89starter-motor circuit, 124

Wwater-spray test, 115, 116Watt, James, 6wattage, 7–9

and AC, 160AC appliance requirements,

173load analysis sheet, 171, 172

208

I N D E X

watts, 5, 6, 7–8waveforms, 157, 175West Marine, 62, 68, 136, 180wet-cell batteries, 67, 68–69, 72,

73wiggle test, 169, 170windings

field, 86stator, 86

wire connectors, 60, 61, 62, 63,64

wire identificationABYC color code, 15–17circuit identification, 17–19

wire sizeAC, 160–61, 162AWG standard vs. SAE stan-

dard, 41–42and circuit breaker sizing,

137–38for DC accessories, 137for electronic equipment, 182manufacturer’s recommenda-

tions, 55, 143rounding up, 43, 144selecting, 42–43and voltage drop, 43, 44, 45,

137, 144wire stripper, 11, 62, 143wire ties, 18, 59, 60wiring

AC, 160–62, 161allowable amperage for con-

ductors, 46, 48, 161, 163

circuit identification, 17–19color coding, 15–17, 18–19,

158–59ignition, 103insulation standards, 43, 46,

47, 48, 161, 162, 163junction boxes, 20–22length for DC accessories,

137locating, 21–22panel feed, 138, 162routing and support, 57–59securing, 141spark plug, 115standards for, 40–59types, 41–42, 137

wiring and connection repairs,59–64

strippers, 11, 62, 143wiring diagrams

bilge blower, 21bilge pump, 143cabin lights, 140CD player, 146component identification,

14–15for DC accessories, 138DGPS receiver, 190, 191double-pole AC circuit

breaker, 164drawing your own, 22–24elements of, 13–14galvanic isolator, 179GPS receiver, 190, 191

need for, 12outboard-engine remote-key,

120poor quality, 15radar, 192shore-power, 159, 160single-pole AC circuit

breaker, 165symbols, 13–14tachometer, 150temperature, fuel, and oil-

pressure gauges, 153wiring harnesses

checking for continuity,132–33

with in-line fuse holder, 183junction boxes, 20–22repairing, 63securing, 58, 59, 60for transducers, 187–88

workshop manuals, 103, 116,118, 124, 125, 132, 176

XXantrex

Link 1000 inverter monitor-ing panel, 174, 175

multiphase smart charger, 99

Zzone of magnetic separation,

145, 181, 182

209

I N D E X

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Powerboater's Guide to Electrical Systems, Second … public/Jurine praktika/Powerboater's... · Malestrom. Maintenance,Troubleshooting, and Improvements Ed Sherman Second Edition