Not so "Good Vibrations"

[specialk]

Weather is nice here, take the boat out last week, not paying too much attention, should have due to drought, but water was the lowest it has ever been. Driving along on normal route, maybe a little off than normal then all of the sudden we feel the boat gradually go from 25mph to 0 in about 30 yards or so. Sandbar. Hop out, and much to my surprise, I was able to walk in all directions about 50 yards with water only up to my knees. Try to get a boat to pull us out to no avail, had to get a barge with a crane to get it out.

Pull it out of the water, and everything looks pristine, no water in boat, tracking fins perfect, no gel coat cracks, prop appears perfect, spins easily. Put it back in water, and I notice some small, but new vibrations, trailer it, and spin up to 3000 rpm, notice the same vibrations, so not due to tracking fins. Examine prop again, no detectable changes, no water coming in from prop shaft.


I assume it has to be the prop or prop shaft. I can send the prop back to ACME for inspections, how hard is the prop shaft to take off and how do I find out if it is true or not.

Any other sources that one can think of, again looks pristine.

[whitlock87]

I would guess it is your prop.

Also just an FYI, never put the boat into gear unless in the water!
If you run the boat in gear while it is on the trailer, you can / will damage the shaft seal.

On the good side, it could have been a lot worse.

I would use a dial indicator to see if the shaft is true.

[specialk]

Trailer was in water, basically making sure that it was not the tracking fins, which I had a very low suspicion

I will send prop off to Acme

[Surf406]

just a thought

check your key way in the prop you might of sheerd it a bit and didnt notice till you pull the prop, if you did it could make the prop wander a bit on the shaft instead of locking in and turning true.

[IDBoating]

Sand packed in the strut bearing?

[boatwakes]

Most likey bent strut which will lead to bent shaft. Eyeball it vertically then check where the shaft passes through the cutlass bearing and see if it's leaning to one side, either X or Y axis. The latter will only be visible if the shaft has had time to rub diagonally into the rubber. I say strut because it, unlike the prop , is not designed to take ANY load, it's only there to hold the shaft true to the transmission output shaft angle. It's also made of bronze which is malleable and morphs into various shapes fairly easily where the prop is a NiBral alloy and far stronger than the strut.