Engine MaintenanceEngine Maintenance

Chapter 7Chapter 7

Outboard Engines and Drives, Outboard Engines and Drives, and Stern Drivesand Stern Drives

22

Objectives for the StudentObjectives for the Student

1.Have a good understanding of the component parts of the outboard marine engine and how these parts work together to propel the boat through the water

2.Have knowledge of the fuel, lubrication, cooling, exhaust, ignition and electrical systems needed for the outboard engine to function properly

3.Have an understanding of the stern drive that is used in inboard/outboard operation

33

The Marine Drive SystemThe Marine Drive SystemOutboard SystemsOutboard Systems

Power Head

Intermediate Housing

Lower Unit

44

Outboard Engine Outboard Engine CrankcaseCrankcase

Similar to conventional Similar to conventional crankcase, but designed crankcase, but designed to work verticallyto work vertically

Different bearing designDifferent bearing design

Dry sump lubricationDry sump lubrication

55

Outboard Engine Outboard Engine CrankshaftCrankshaft

Bearings are Bearings are designed for designed for vertical vertical operationoperation

Relies on mist Relies on mist lubricationlubrication

66

Outboard Engine PistonsOutboard Engine Pistons

Long skirt to valve intake and exhaust portsLong skirt to valve intake and exhaust ports

No oil control groovesNo oil control grooves

Domed head to scavenge cylinder gasesDomed head to scavenge cylinder gases

77

Outboard CarburetionOutboard Carburetion

Multiple carburetors are commonMultiple carburetors are common Individual carburetors are simpler than inboard Individual carburetors are simpler than inboard

engine designsengine designs

88

Outboard LubricationOutboard Lubrication

Oil mist lubricationOil mist lubrication Usually requires oil and fuel to be Usually requires oil and fuel to be

premixedpremixed Can be injected from oil reservoirCan be injected from oil reservoir

No sump requiredNo sump required No oil cooling benefitNo oil cooling benefit

99

Outboard Cooling and Outboard Cooling and ExhaustExhaust

Cooling derived Cooling derived from impeller from impeller pump in lower unitpump in lower unit

Most water cools Most water cools the exhaustthe exhaust

Exhaust is vented Exhaust is vented through the through the propeller hubpropeller hub

1010

Outboard IgnitionOutboard Ignition

MagnetoMagneto Coil energy is Coil energy is

provided by magnet provided by magnet in engine flywheelin engine flywheel

Distributor / Distributor / breaker pointbreaker point Same as inboard Same as inboard

enginesengines Solid stateSolid state

1111

Outboard Drive SystemsOutboard Drive Systems

1212

I/O Drive SystemsI/O Drive Systems

Inboard engineInboard engine Outboard drive Outboard drive

systemsystem Generally pierces Generally pierces

the transom, not the transom, not the hullthe hull

1313

Tilt and Trim SystemsTilt and Trim Systems

Mechanical on Mechanical on small drivessmall drives

Hydroelectric on Hydroelectric on larger systemslarger systems

1414

Routine MaintenanceRoutine Maintenance

Service twice per seasonService twice per season Check lower unit lubricant and Check lower unit lubricant and

replace if necessaryreplace if necessary Replace zincs as needed (when Replace zincs as needed (when

>50% consumed)>50% consumed) Check boots and seals for cracksCheck boots and seals for cracks

1515

Winter StorageWinter Storage

Prevent freezingPrevent freezing Check and replace lubricant as neededCheck and replace lubricant as needed

Replace zincs as needed (when >50% Replace zincs as needed (when >50% consumed) consumed)

Warm the engine, then change the oilWarm the engine, then change the oil Run potable antifreeze through the raw Run potable antifreeze through the raw

water systemwater system Check boots and seals for cracksCheck boots and seals for cracks Paint housing if neededPaint housing if needed

1616

Spring ServiceSpring Service

Should not be necessary!Should not be necessary!

1717

Remember…Remember…

You should be able to You should be able to identify problems and identify problems and explain them to a mechanicexplain them to a mechanic