Engine MaintenanceEngine Maintenance

Chapter 1Chapter 1

What Makes the Boat GoWhat Makes the Boat Go

22

Objectives for the StudentObjectives for the Student

1.Have a good grasp of the components of the modern marine propulsion system

2.Have an understanding of the principles of the modern marine engine, both two stroke and four stroke

3.Have an understanding of the general troubleshooting methodologies that can be used and repair work that needs to be done

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The Marine EngineThe Marine Engine

Needed for combustion:Needed for combustion: fuelfuel air (oxygen)air (oxygen) ignition sourceignition source

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The Marine EngineThe Marine Engine

A compressed fuel/air mixture is ignitedA compressed fuel/air mixture is ignited

Burning mixture increases in temperature and Burning mixture increases in temperature and pressurepressure

Expansion of gas is converted to linear piston Expansion of gas is converted to linear piston motionmotion

Crank converts linear motion to rotary motionCrank converts linear motion to rotary motion

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The Marine EngineThe Marine Engine

IntakeIntake fuel/air enters fuel/air enters

the the combustion combustion chamberchamber

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The Marine EngineThe Marine Engine

CompressionCompression mixture is mixture is

compressed compressed within the within the cylindercylinder

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The Marine EngineThe Marine Engine

Power Power compressed compressed

charge is charge is ignited to move ignited to move the piston the piston downwarddownward

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The Marine EngineThe Marine Engine

ExhaustExhaust spent gases spent gases

are expelledare expelled

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The Diesel EngineThe Diesel Engine

IntakeIntake air enters the air enters the

combustion combustion chamberchamber

1010

The Diesel EngineThe Diesel Engine

CompressionCompression air is air is

compressed compressed to high to high temperaturetemperature

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The Diesel EngineThe Diesel Engine

PowerPower fuel is fuel is

injected and injected and autoignitesautoignites

1212

The Diesel EngineThe Diesel Engine

ExhaustExhaust the spent the spent

gases are gases are expelledexpelled

1313

DisplacementDisplacement

Cylinder DisplacementCylinder Displacement The total volume of air that can be moved in The total volume of air that can be moved in

one engine cycle for one cylinderone engine cycle for one cylinder BoreBore

Diameter of the cylinderDiameter of the cylinder

StrokeStroke Total piston travel from Total piston travel from

TDC to BDCTDC to BDC

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DisplacementDisplacement

Volume of a Right Circular CylinderVolume of a Right Circular Cylinder

• V = r2 h

• where

• V = volume

• = 3.1416

• r = radius (1/2 diameter) of cylinder

• h = height of the cylinder (stroke)

r

h

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DisplacementDisplacement

Engine DisplacementEngine Displacement The total volume of one cylinder’s The total volume of one cylinder’s

displacement, times the number of cylindersdisplacement, times the number of cylinders

• Displacement = n V = n r2 h

• where

• n = number of cylinders

•V = volume of one cylinder

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DisplacementDisplacement

Example: Chevrolet 350 V-8Example: Chevrolet 350 V-8 Bore = 4.00 inches (10.16 cm)Bore = 4.00 inches (10.16 cm) Stroke = 3.48 inches (8.84 cm)Stroke = 3.48 inches (8.84 cm)

Displacement = n V = n Displacement = n V = n rr22 h h

Displacement = 8 x 3.1416 Displacement = 8 x 3.1416 x (2.00 inches)x (2.00 inches)22 x 3.48 x 3.48 inchesinches

Displacement = 350 Displacement = 350 inchesinches33 or 350 cubic inches or 350 cubic inches or 350 cubic inches or 350 cubic inches displacement or 350 CIDdisplacement or 350 CID

Displacement = n V = n Displacement = n V = n rr22 h h

Displacement = 8 x 3.1416 Displacement = 8 x 3.1416 x (5.08 cm)x (5.08 cm)22 x 8.84 cm x 8.84 cm

Displacement = 5735 cc or Displacement = 5735 cc or 5.7 liters5.7 liters

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Size MattersSize Matters

Engines of Greater Displacement Engines of Greater Displacement Generally Deliver More HorsepowerGenerally Deliver More Horsepower More fuel/air consumed per strokeMore fuel/air consumed per stroke More heat releasedMore heat released More power producedMore power produced

1818

Engine CompressionEngine Compression

Compression RatioCompression Ratio The cylinder’s total volume at BDC, divided by The cylinder’s total volume at BDC, divided by

volume at TDCvolume at TDC

• Compression Ratio = V / v

• where

• V = volume at BDC• BDC = bottom dead center

• v = volume at TDC

• TDC = top dead center

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Engine CompressionEngine Compression Compression Ratio = V / vCompression Ratio = V / v

V = 8.8496 cubic inches (145 cc)V = 8.8496 cubic inches (145 cc) v = 1.0411 cubic inches (17 cc)v = 1.0411 cubic inches (17 cc)

V / v = 8.8496 / 1.0411 = 8.5:1V / v = 8.8496 / 1.0411 = 8.5:1 V / v = 145 / 17 = 8.5:1V / v = 145 / 17 = 8.5:1

2020

Horsepower and TorqueHorsepower and Torque

HorsepowerHorsepower measure of workmeasure of work 1 hp = 745 watts1 hp = 745 watts

TorqueTorque measure of rotational forcemeasure of rotational force

pounds-foot (lb-ft)pounds-foot (lb-ft) Newton-meter (Nm)Newton-meter (Nm)

2121

The Marine Drive SystemThe Marine Drive System

Three Basic Types of Marine Drives:Three Basic Types of Marine Drives: OutboardOutboard InboardInboard Stern Drive, also known as Stern Drive, also known as

Inboard/Outboard or I/O driveInboard/Outboard or I/O drive

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The Marine Drive SystemThe Marine Drive SystemOutboard SystemsOutboard Systems

Power Head

Intermediate Housing

Lower Unit

2323

The Marine Drive SystemThe Marine Drive SystemInboard SystemsInboard Systems

2424

The Marine Drive SystemThe Marine Drive SystemStern Drive (I/O) SystemsStern Drive (I/O) Systems

2525

Thrust UnitsThrust Units PropellerPropeller

2-4 blade (inboards)2-4 blade (inboards) 3-6 blades (outboards)3-6 blades (outboards)

PitchPitch measure of advance (one measure of advance (one

rotation through a solid rotation through a solid object)object)

DiameterDiameter diameter of a circle that diameter of a circle that

describes the blade tipsdescribes the blade tips

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Thrust UnitsThrust Units

Water JetWater Jet Internal impellerInternal impeller Good for shallow water operationGood for shallow water operation Directs thrust using steerable Directs thrust using steerable

nozzle and reverse gatenozzle and reverse gate

2727

General Troubleshooting General Troubleshooting MethodologyMethodology

Check the ObviousCheck the Obvious Check the EasyCheck the Easy Check SystematicallyCheck Systematically Make No Erratic AdjustmentsMake No Erratic Adjustments

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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