Engineering · Propulsion — Stern Tube
An oil-lubricated stern tube bearing is sealed at the after end to:
- AKeep lube oil in and seawater out around the propeller shaft✓ Correct
- BCool the propeller
- CProvide thrust
- DIncrease shaft RPM
Explanation
The stern tube supports the propeller shaft where it passes through the hull. Oil-lubricated tubes use aft (and forward) lip seals to retain lubricating oil and exclude seawater; seal failure shows as oil loss or water contamination of the stern tube oil.
Authority: Modern Marine Engineer's Manual; shafting
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