Engine Maintenance Chapter 6 Inboard Drive Systems

2 Objectives 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

3 Reduction Gearing Optimizes engine speed and propeller speed Optimizes engine speed and propeller speed Typically 1.5:1, 1.9:1, 2.1:1, etc. Typically 1.5:1, 1.9:1, 2.1:1, etc. Example Example 2.1:1 means engine is running at 2,100 rpm while propeller is turning at 1,000 rpm 2.1:1 means engine is running at 2,100 rpm while propeller is turning at 1,000 rpm Lower speed means higher torque Lower speed means higher torque

4 Straight Drive Train The entire drive system is angled to pass through the hull The entire drive system is angled to pass through the hull

5 Angled Drive Train Output shaft is offset 8-12 degrees Output shaft is offset 8-12 degrees

6 Vee Drive Permits engine to be placed further aft in hull Permits engine to be placed further aft in hull

7 Inboard Performance System

8 Propellers Blades Blades number of blades generally increases with power requirements number of blades generally increases with power requirements Diameter Diameter outside edge to outside edge across center outside edge to outside edge across center larger diameters need more torque to drive them larger diameters need more torque to drive them Pitch Pitch distance of advance for one revolution distance of advance for one revolution Other characteristics Other characteristics shape, cupping, rake shape, cupping, rake

9 Propeller Performance Boat speed and engine speed are key Boat speed and engine speed are key Optimize both! Optimize both! Best speed is the rated boat speed at wide open throttle Best speed is the rated boat speed at wide open throttle

10 Jet Drive Flush mounted for shallow water operation Flush mounted for shallow water operation

11 Specialty Drive Systems Trolling motors are electric motors used for low speed application Trolling motors are electric motors used for low speed application Bow and stern thrusters are used for close-in maneuvering Bow and stern thrusters are used for close-in maneuvering

12 Routine Maintenance Oil level Oil level Transmission fluid level Transmission fluid level Impeller pump Impeller pump Transmission oil cooler (may clog with impeller bits) Transmission oil cooler (may clog with impeller bits) Water intake strainer Water intake strainer Hoses and clamps Hoses and clamps

13 Vee Drive Maintenance Same as standard inboard, plus… Same as standard inboard, plus… Keep an eye on the transmission Keep an eye on the transmission

14 Propeller Maintenance Inspect for chips, nicks, dents, etc. Inspect for chips, nicks, dents, etc. Check for cavitation damage (small pits) Check for cavitation damage (small pits)

15 Jet Drive Maintenance Same as standard inboard, plus… Same as standard inboard, plus… Special manufacturer’s requirements for the drive unit Special manufacturer’s requirements for the drive unit

16 Winter Storage Prevent freezing Prevent freezing Haul out Haul out Run potable antifreeze through raw water system Run potable antifreeze through raw water system Warm the engine, then change the oil Warm the engine, then change the oil Maintain transmission fluid Maintain transmission fluid If hauled out, disconnect the drive shaft coupling If hauled out, disconnect the drive shaft coupling

17 Spring Service Check stuffing box Check stuffing box If hauled over the winter: If hauled over the winter: Allow the boat to sit in the water for five days Allow the boat to sit in the water for five days Reconnect drive shaft coupling and check alignment Reconnect drive shaft coupling and check alignment Replace raw water impeller Replace raw water impeller Check stuffing box again Check stuffing box again

18 Remember… You should be able to identify problems and explain them to a mechanic