engine vibration

[RonBarr]

Following an anchor line wrapping around the prop recently I have noticed extreme vibration when throttling up our Yanmar between 900 and 1500 rpm.approx - it smooths out after that but the vibrations feel like the shaft is going to fly off! Nothing seems amiss when diving although not in great visibility. Anyone had a similar experience?

Ron B
Hoyt 32

[N1YDY]

what type of prop do you have? could a blade have been bent? if the prop folds or feathers, could it have been damaged, or might there be some debris stuck in it? could the cutlass bearing or strut been damaged? just some ideas, and good luck! i had a bit of rope get stuck in my max-prop once. it prevented one of the three blades from acheiving the correct pitch, and caused vibration. unlike your situation, however, the vibration was evident at all rpms.

Hank

[Michel]

Anyone had a similar experience?

Ron B
Hoyt 32

Yes, I once drifted over a standing fishing net with the engine and prop running slowly. The straight keel of the F33 (centerboard was up) slid over steel wire on the top of the net. Propshaft was bent and the engine mounts on one side torn. You could have a slightly bent prop blade as well.

[GeoffSchultz]

The alignment could be off caused by a failing/loose motor mount.

-- Geoff

[THATBOATGUY]

I'm going plus one on checking for broken mounts and bent shaft.

George

[Rick Simonds]

Add another guess for a bent prop shaft and/or propeller blade. The fact that the vibration gets better at higher speeds while moving makes me suspect the prop strut/cutlass bearing, too (a floppy cutlass will often stabilize at higher RPM.)

I hit a floating board once, stopping the engine instantly dead. It made a mess of everything. A machine shop can straighten everything back out.