Prop Noise

[ben373]

On my 37 benne I recently changed the prop from a folding Volvo to a fixed low drag.

The old Volvo was was worn out and vibrated. The new is nice and smooth but gets a noise when powering up which I think is cavitation noise.

Got caught in a choppy sea recently and the noise was very evident.

The prop maybe slightly overpitched.

Is this noise normal or do I have some other problem? The noise was not there with the Volvo prop.

Thanks

[Nicholson58]

Is the pitch and other blade criteria similar to the old prop? If its digging too hard it could be cavitation. Does the boat perform differently? leser or greater acceleration from stopped? Top speed? Speed with respect to rpm? Do you see a change in engine temperature? Cavitation can usually be stopped by backing off throttle.

[delmarrey]

What size is the prop shaft, and how long is it?

You could be whipping the shaft with the new torque.

[ben373]

Thanks for the reply. I am getting slightly more speed the engine is not overheating and the boat is going nicely. Is the noise anything to worry about. The prop maker suggests maybe going up 1 on the pitch because it is a low drag fixed prop. The blades are narrow.

[delmarrey]

Have someone go below while accelerating to watch the shaft. If it's whipping, then it'll need to be de-pitched a bit.