Engineering · Propulsion — Reduction Gear
A reduction gear between a high-speed diesel and the propeller shaft is fitted to:
- AIncrease propeller RPM above engine RPM
- BReverse the direction of the engine
- CAllow the engine to run at its efficient high speed while the propeller turns at a slower, more efficient speed✓ Correct
- DIncrease fuel pressure
Explanation
Diesels are efficient at relatively high RPM, but propellers are efficient at lower RPM with larger diameter. The reduction gear matches the two, and on many installations also provides for clutching and reversing.
Authority: Modern Marine Engineer's Manual; marine propulsion
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