engine maintenance chapter 6 inboard drive systems
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Engine MaintenanceEngine Maintenance
Chapter 6Chapter 6
Inboard Drive SystemsInboard Drive Systems
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Objectives for the StudentObjectives for the Student
1.Have an understanding of the various drive systems associated with inboard marine engines
2.Have knowledge of the design of marine propellers and how the various configurations affect the boat’s performance
3.Have basic knowledge of how to perform routine maintenance of inboard drive systems
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Reduction GearingReduction Gearing
Optimizes engine speed and Optimizes engine speed and propeller speedpropeller speed
Typically 1.5:1, 1.9:1, 2.1:1, etc.Typically 1.5:1, 1.9:1, 2.1:1, etc.
ExampleExample 2.1:1 means engine is running at 2.1:1 means engine is running at
2,100 rpm while propeller is turning at 2,100 rpm while propeller is turning at 1,000 rpm1,000 rpm
Lower speed means higher torqueLower speed means higher torque
44
Straight Drive TrainStraight Drive Train
The entire drive system is angled The entire drive system is angled to pass through the hullto pass through the hull
55
Angled Drive TrainAngled Drive Train
Output shaft is offset 8-12 Output shaft is offset 8-12 degreesdegrees
66
Vee DriveVee Drive
Permits engine to be placed Permits engine to be placed further aft in hullfurther aft in hull
77
Inboard Performance Inboard Performance SystemSystem
88
PropellersPropellers BladesBlades
number of blades generally increases with number of blades generally increases with power requirementspower requirements
DiameterDiameter outside edge to outside edge across centeroutside edge to outside edge across center larger diameters need more torque to drive larger diameters need more torque to drive
themthem PitchPitch
distance of advance for one revolutiondistance of advance for one revolution Other characteristicsOther characteristics
shape, cupping, rakeshape, cupping, rake
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Propeller PerformancePropeller Performance
Boat speed and engine speed Boat speed and engine speed are keyare key Optimize both!Optimize both!
Best speed is the rated boat Best speed is the rated boat speed at wide open throttlespeed at wide open throttle
1010
Jet DriveJet Drive
Flush mounted for shallow Flush mounted for shallow water operationwater operation
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Specialty Drive SystemsSpecialty Drive Systems
Trolling motors are electric Trolling motors are electric motors used for low speed motors used for low speed applicationapplication
Bow and stern thrusters are Bow and stern thrusters are used for close-in maneuveringused for close-in maneuvering
1212
Routine MaintenanceRoutine Maintenance
Oil levelOil level Transmission fluid levelTransmission fluid level Impeller pumpImpeller pump Transmission oil cooler (may clog Transmission oil cooler (may clog
with impeller bits)with impeller bits) Water intake strainerWater intake strainer Hoses and clampsHoses and clamps
1313
Vee Drive MaintenanceVee Drive Maintenance
Same as standard inboard, plus…Same as standard inboard, plus… Keep an eye on the transmissionKeep an eye on the transmission
1414
Propeller MaintenancePropeller Maintenance
Inspect for chips, nicks, dents, Inspect for chips, nicks, dents, etc.etc.
Check for cavitation damage Check for cavitation damage (small pits)(small pits)
1515
Jet Drive MaintenanceJet Drive Maintenance
Same as standard inboard, Same as standard inboard, plus…plus…
Special manufacturer’s Special manufacturer’s requirements for the drive unitrequirements for the drive unit
1616
Winter StorageWinter Storage
Prevent freezingPrevent freezing Haul outHaul out Run potable antifreeze through raw Run potable antifreeze through raw
water systemwater system Warm the engine, then change the Warm the engine, then change the
oiloil Maintain transmission fluidMaintain transmission fluid If hauled out, disconnect the drive If hauled out, disconnect the drive
shaft couplingshaft coupling
1717
Spring ServiceSpring Service
Check stuffing boxCheck stuffing box If hauled over the winter:If hauled over the winter:
Allow the boat to sit in the water for Allow the boat to sit in the water for five daysfive days
Reconnect drive shaft coupling and Reconnect drive shaft coupling and check alignmentcheck alignment
Replace raw water impellerReplace raw water impeller Check stuffing box againCheck stuffing box again
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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
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