Engine MaintenanceEngine Maintenance

Chapter 2Chapter 2

Inboard Spark Ignition Inboard Spark Ignition EnginesEngines

Part 1Part 1

22

Objectives for the StudentObjectives for the Student

1.Have a good understanding of the component parts of the marine gasoline engine and how these parts work together to perform the useful function of propelling the boat

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

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What’s Covered in This ChapterWhat’s Covered in This Chapter

Engine ComponentsEngine Components engine blockengine block cylinders and cylinder headscylinders and cylinder heads crankshaft, pistons, and connecting crankshaft, pistons, and connecting

rodsrods valve trainvalve train manifoldsmanifolds

Associated Systems Required for Associated Systems Required for OperationOperation fuel systemsfuel systems cooling systemscooling systems exhaust systemsexhaust systems lubrication systemslubrication systems ignition systemsignition systems electrical and starting systemselectrical and starting systems

44

Engine ComponentsEngine Components

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

55

Engine ComponentsEngine Components

Engine BlockEngine Block largest single component largest single component

of an inboard spark of an inboard spark ignition engineignition engine

principle purpose Is to principle purpose Is to enclose the cylinders and enclose the cylinders and provide support for the provide support for the crankshaftcrankshaft

may be either Inline, Vee, may be either Inline, Vee, or Opposed in design or Opposed in design

A Vee Type Engine Block. The Crankshaft Is Not Shown

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Engine ComponentsEngine Components

CylindersCylinders perfectly round perfectly round

holes in the engine holes in the engine blockblock

sides are finely sides are finely finished to a finished to a smooth surfacesmooth surface

pistons ride up and pistons ride up and down inside the down inside the cylinderscylinders

Cut Away of an Engine Block to Show the Cylinders.

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Engine ComponentsEngine Components Engine Cylinder Engine Cylinder

ConfigurationsConfigurations InlineInline

VeeVee

OpposedOpposed

Diagram of a 6 Cylinder InlineEngine Block with Last Two Cylinders Cut Away

Cut Away Drawing of a V-8 Engine

The Opposed Engine is basically a flattened vee design. It is sometimes referred to as a "pancake engine"

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CrankshaftCrankshaft

Primary Rotating Primary Rotating ComponentComponent

Converts Converts Reciprocating Reciprocating Motion to Rotary Motion to Rotary MotionMotion

High-Tensile SteelHigh-Tensile Steel

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Piston, Rings, Connecting RodPiston, Rings, Connecting Rod

PistonsPistons pushed down by pushed down by

burning fuelburning fuel top is part of the top is part of the

combustion combustion chamberchamber

RingsRings seal piston within seal piston within

cylindercylinder Connecting RodsConnecting Rods

connect piston to connect piston to crankshaftcrankshaft

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Engine ComponentsEngine Components

Flywheel (on Flywheel (on transmission end transmission end of crankshaft)of crankshaft) maintains maintains

momentum momentum between power between power strokesstrokes

Vibration Damper Vibration Damper (on other end of (on other end of crankshaft)crankshaft) offsets torsional offsets torsional

vibrationvibration

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Oil PanOil Pan

Oil Reservoir Oil Reservoir on Bottom of on Bottom of Engine BlockEngine Block

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CamshaftCamshaft

Provides TimingProvides Timing intake and intake and

exhaust valvesexhaust valves either spark plug either spark plug

or fuel injectoror fuel injector Rotates (chain or Rotates (chain or

gear driven)gear driven) 4-cycle engines: 4-cycle engines:

at half crankshaft at half crankshaft speedspeed

2-cycle engines: 2-cycle engines: at crankshaft at crankshaft speedspeed

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ValvesValves

Intake and Exhaust Valves Open into CylindersIntake and Exhaust Valves Open into Cylinders Most are Opened by Camshaft Pressure and Most are Opened by Camshaft Pressure and

Closed by Strong SpringClosed by Strong Spring

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ManifoldsManifolds

IntakeIntake carburetor to cylinder head (induction)carburetor to cylinder head (induction)

ExhaustExhaust exhaust block (exhaust valves) to mufflerexhaust block (exhaust valves) to muffler exhaust elbow is raw water cooledexhaust elbow is raw water cooled

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Summary – Engine ComponentsSummary – Engine Components

Major Marine Engine ComponentsMajor Marine Engine Components crankcase or cylinder blockcrankcase or cylinder block cylinders and cylinder headscylinders and cylinder heads crankshaftcrankshaft pistons, rings, connecting rodspistons, rings, connecting rods flywheel, vibration damperflywheel, vibration damper oil panoil pan camshaftcamshaft valvesvalves manifoldsmanifolds

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Associated SystemsAssociated Systems

Fuel SystemFuel System Cooling SystemCooling System Exhaust SystemExhaust System Lubrication SystemLubrication System Ignition SystemIgnition System Electrical and Starting SystemsElectrical and Starting Systems

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Fuel SystemFuel System

Gasoline is the Fuel for Inboard Spark Gasoline is the Fuel for Inboard Spark Ignition EnginesIgnition Engines

Gasoline is Mixed with Oxygen (Air) Gasoline is Mixed with Oxygen (Air) Before It Enters the Combustion Before It Enters the Combustion ChamberChamber

Work Done Depends on Heat Obtained Work Done Depends on Heat Obtained from Burning the Fuelfrom Burning the Fuel

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Fuel SystemFuel System

Gasoline is Ranked by Octane NumberGasoline is Ranked by Octane Number Higher octane number burns at higher Higher octane number burns at higher

temperaturetemperature Higher octane number provides a stable, Higher octane number provides a stable,

controlled burncontrolled burn Low octane sometimes ignites Low octane sometimes ignites

prematurely, resulting in “pinging” or prematurely, resulting in “pinging” or “knocking”“knocking”

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Fuel SystemFuel System

When RefuelingWhen Refueling close all hatches and extinguish all flamesclose all hatches and extinguish all flames good contact between nozzle and fuel pipegood contact between nozzle and fuel pipe

Fuel TankFuel Tank properly installed and well ventedproperly installed and well vented periodically inspected for fuel leaksperiodically inspected for fuel leaks

BilgesBilges run blowers for at least 5 minutes before starting enginerun blowers for at least 5 minutes before starting engine before starting gas engines, sniff bilge for gas fumesbefore starting gas engines, sniff bilge for gas fumes

Safety Precautions With Gasoline

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Fuel SystemFuel System

Components of the Fuel Components of the Fuel SystemSystem carburetors or fuel injection carburetors or fuel injection

systemsystem fuel pumpfuel pump fuel filterfuel filter

CarburetorCarburetor vaporizes gasolinevaporizes gasoline throttle controls fuel volumethrottle controls fuel volume

SimplifiedCarburetor

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Fuel SystemFuel System Electronic Fuel InjectionElectronic Fuel Injection

delivers more power than carburetorsdelivers more power than carburetors fuel is metered into the air intake streamfuel is metered into the air intake stream controlled by several sensorscontrolled by several sensors

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Fuel SystemFuel System Fuel PumpsFuel Pumps

mechanical low pressure diaphragmmechanical low pressure diaphragm may be electricmay be electric

Intake

Discharge

2323

Fuel SystemFuel System Flame ArrestorsFlame Arrestors

grid of closely space metal louvers, which allow free grid of closely space metal louvers, which allow free air flow but immediately extinguish any flameair flow but immediately extinguish any flame

Flame Arrestors are Required by Federal Law (all Flame Arrestors are Required by Federal Law (all boats manufactured after 1948)boats manufactured after 1948) even on fuel injected gasoline engineseven on fuel injected gasoline engines

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Cooling SystemsCooling Systems Proper CoolingProper Cooling

temperatures above:temperatures above: 400 F (204 C) may break down lubrication400 F (204 C) may break down lubrication 500 F (260 C) may burn valve seats500 F (260 C) may burn valve seats

aluminum begins to lose its strengthaluminum begins to lose its strength Water in Water Jacket Removes 90% of Water in Water Jacket Removes 90% of

Waste HeatWaste Heat Lubrication in Engine Removes 10% of Lubrication in Engine Removes 10% of

Waste HeatWaste Heat Must Have Airflow Outside of EngineMust Have Airflow Outside of Engine Overcooling May Cause Poor Lubrication Overcooling May Cause Poor Lubrication

and Alter Engine Clearancesand Alter Engine Clearances

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Cooling SystemsCooling Systems Direct (or Open) CoolingDirect (or Open) Cooling

engine is cooled by seawaterengine is cooled by seawater disadvantage: engine exposed to raw (salt) disadvantage: engine exposed to raw (salt)

waterwater Indirect (or Closed) CoolingIndirect (or Closed) Cooling

engine is cooled by coolantengine is cooled by coolant mixture of antifreeze and clean (distilled) mixture of antifreeze and clean (distilled)

waterwater coolant is then cooled by seawater in heat coolant is then cooled by seawater in heat

exchangerexchanger disadvantage: requires heat exchangerdisadvantage: requires heat exchanger

2626

Cooling SystemsCooling Systems

Direct

Simplified Schematic

2727

Cooling SystemsCooling Systems

Indirect(note heat exchanger)

Simplified Schematic

2828

Cooling SystemsCooling Systems

Keel Cooler

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PumpsPumps Normally belt driven from engineNormally belt driven from engine

Cooling SystemsCooling Systems

Impeller(Rotary)

Centrifugal

Gear

3030

Cooling SystemCooling System ThermostatThermostat

temperature-sensitive device used to temperature-sensitive device used to maintain correct operating temperaturemaintain correct operating temperature

Ratings: 145 F (63 C) and 195 F (90 C)Ratings: 145 F (63 C) and 195 F (90 C) fully open at approximately 20 F (11 C) over fully open at approximately 20 F (11 C) over

ratingrating

3131

Exhaust SystemsExhaust Systems

Exhaust Gases are Extremely Hot and Exhaust Gases are Extremely Hot and PoisonousPoisonous

Two Types of Exhaust: Wet and DryTwo Types of Exhaust: Wet and Dry wet is preferred and safestwet is preferred and safest

Exhaust System Must Not Ingest WaterExhaust System Must Not Ingest Water anti-siphon break (vacuum valve)anti-siphon break (vacuum valve)

Exhaust Mixing Elbow

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Exhaust SystemsExhaust Systems Sailboat Exhaust Risers are Normally Below Sailboat Exhaust Risers are Normally Below

Waterline (especially when heeling)Waterline (especially when heeling) In Such a Case, an Anti-Siphon Valve is Needed In Such a Case, an Anti-Siphon Valve is Needed

to Let Air into the Exhaust Line (break vacuum)to Let Air into the Exhaust Line (break vacuum)

Typical Sailboat Typical Inboard Powerboat

Elbow below water line; may permit siphoning of seawater into engine

Elbow above water line; no siphoning effect

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Lubrication SystemsLubrication Systems

Purpose of OilPurpose of Oil Characteristics of OilCharacteristics of Oil Lubrication SystemsLubrication Systems Oil PumpsOil Pumps Oil FiltersOil Filters Compounds and SealsCompounds and Seals

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Lubrication SystemsLubrication Systems

Purpose of OilPurpose of Oil oil reduces friction between moving partsoil reduces friction between moving parts

PurposePurpose lubrication – slippery surface between lubrication – slippery surface between

moving partsmoving parts seal – between piston rings and cylinder seal – between piston rings and cylinder

surfacesurface cool – especially bearingscool – especially bearings clean – contaminants held in suspensionclean – contaminants held in suspension

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Lubrication SystemsLubrication Systems Characteristics of OilCharacteristics of Oil

Viscosity and DetergencyViscosity and Detergency viscosity is the oil’s resistance to flowviscosity is the oil’s resistance to flow changes with temperaturechanges with temperature SAE numbers: the lower the number, the SAE numbers: the lower the number, the

thinner the oilthinner the oil Detergency is the oil’s ability to cleanDetergency is the oil’s ability to clean

change oil while warm to remove contaminantschange oil while warm to remove contaminants Foaming – trapped air bubbles in the oilFoaming – trapped air bubbles in the oil

reduces lubrication effectivenessreduces lubrication effectiveness major cause is overfilling of crankcasemajor cause is overfilling of crankcase

3636

Lubrication SystemsLubrication Systems

Lubrication System of a Typical 4-Cycle EngineLubrication System of a Typical 4-Cycle Engine

3737

Lubrication SystemsLubrication Systems Oil FiltersOil Filters

remove foreign particles from the oilremove foreign particles from the oil canister typecanister type replaceable elementreplaceable element full-flow (filters all) and bypass type (filters some)full-flow (filters all) and bypass type (filters some)

Caution: do not interchangeCaution: do not interchange

NoteBypassValve

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Lubrication SystemsLubrication Systems Anti-seize CompoundsAnti-seize Compounds

soft metal particles soft metal particles suspended in grease-like suspended in grease-like vehiclevehicle

reduce the probability of reduce the probability of parts rusting togetherparts rusting together

used on threads, nuts, studs, used on threads, nuts, studs, boltsbolts

SealsSeals used to seal lubrication on used to seal lubrication on

shaftsshafts if leaking, must be replacedif leaking, must be replaced

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Lubrication SystemsLubrication Systems SummarySummary

purpose of oil: lubricate, seal, cool, cleanpurpose of oil: lubricate, seal, cool, clean characteristics: viscosity and detergencycharacteristics: viscosity and detergency oil filters: remove foreign particles from oiloil filters: remove foreign particles from oil periodically check oil – don’t overfillperiodically check oil – don’t overfill follow manufacturer's recommendations follow manufacturer's recommendations

for oilfor oil Change oil and filterChange oil and filter

every 100 hours (doesn’t wear out, just gets every 100 hours (doesn’t wear out, just gets dirty)dirty)

before winter storagebefore winter storage

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Ignition SystemsIgnition Systems

DistributorDistributor Condenser and Breaker PointsCondenser and Breaker Points Other Ignition SystemsOther Ignition Systems CoilCoil Spark Plug WireSpark Plug Wire Spark PlugsSpark Plugs

4141

Ignition SystemsIgnition Systems

Battery and Alternator are Primary Sources of Battery and Alternator are Primary Sources of EnergyEnergy

Ignition Coil Produces High Voltage for Spark Ignition Coil Produces High Voltage for Spark PlugsPlugs

4242

Ignition SystemsIgnition Systems Distributor Delivers Spark to Each CylinderDistributor Delivers Spark to Each Cylinder

at the specific instant when the breaker points at the specific instant when the breaker points openopen

4343

Ignition SystemsIgnition Systems Points and CondenserPoints and Condenser

old technologyold technology condenser prolongs the life of the points by reducing condenser prolongs the life of the points by reducing

arcingarcing breaker points switch the coil’s primary circuitbreaker points switch the coil’s primary circuit

Gap is Adjustable

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Ignition SystemsIgnition Systems Solid State IgnitionSolid State Ignition

points control a transistor (not full coil points control a transistor (not full coil current)current)

increased point life; condenser not requiredincreased point life; condenser not required hotter spark than conventionalhotter spark than conventional can be converted to solid statecan be converted to solid state

Capacitor-Discharge IgnitionCapacitor-Discharge Ignition variation of transistorized ignitionvariation of transistorized ignition much hotter spark (hotter than solid state)much hotter spark (hotter than solid state)

Electronic IgnitionElectronic Ignition replaces points with a control modulereplaces points with a control module individual ignition coil for each spark plugindividual ignition coil for each spark plug computer controlledcomputer controlled

4545

Electrical and Starting Electrical and Starting SystemsSystems

Boat BatteriesBoat Batteries Battery ChargingBattery Charging Starting SystemsStarting Systems Fuses and Circuit BreakersFuses and Circuit Breakers WiringWiring

4646

Electrical and Starting Electrical and Starting SystemsSystems

Battery SelectionBattery Selection classificationclassification

Starting: provides high current for a short time but is Starting: provides high current for a short time but is ruined by deep dischargesruined by deep discharges

Deep-Cycle: constructed to tolerate repeated deep Deep-Cycle: constructed to tolerate repeated deep discharges – good for use as House batteriesdischarges – good for use as House batteries

Dual Purpose: provides high starting current and can Dual Purpose: provides high starting current and can withstand deep dischargeswithstand deep discharges

technologiestechnologies Flooded-Cell: regular lead/acid storage batteryFlooded-Cell: regular lead/acid storage battery Gelled Electrolyte: sealed, maintenance freeGelled Electrolyte: sealed, maintenance free Absorbed Glass Mat: glass fiber mats saturated with Absorbed Glass Mat: glass fiber mats saturated with

water-diluted sulfuric acidwater-diluted sulfuric acid

4747

Charging SystemsCharging Systems

Generators: No Longer in ProductionGenerators: No Longer in Production AlternatorsAlternators

driven off engine with vee beltdriven off engine with vee belt use diodes to convert AC output to DC for use diodes to convert AC output to DC for

battery chargingbattery charging will charge batteries, even at low engine rpmwill charge batteries, even at low engine rpm

4848

Starting SystemsStarting Systems

Electric Starters are Low Voltage, Direct Electric Starters are Low Voltage, Direct Current Motors Used to Crank the EngineCurrent Motors Used to Crank the Engine

Starter Starter ComponentsComponents frameframe armaturearmature brushesbrushes field windings field windings drive mechanismdrive mechanism

4949

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