Nautique 230 vibration issue

[hal2814]

Today while out at the lake our 2011 Nautique 230 suddenly started violently shaking at anything above idle. We made it back to the boat ramp. I thought for sure the prop was damaged but when I pulled the boat out the prop looked fine. I got it home and looked for engine codes in LINC but couldn’t find any. While I was looking it over I noticed the prop was loose on the shaft. Could that cause the vibration? It’s my understanding the prop is firm against the shaft while moving forward. In the morning I intend to drop the boat in and see if the vibration went away after tightening the prop nut. If it does, I have a brand new nylon nut I’ll probably put on. Is there anything else I should check our while I’m out there tomorrow? I’m also concerned with how the prop got loose to begin with. We changed the prop but that was last August and we’ve been out about a dozen times since then.

[Stevemo14]

Did you replace the prop nut cotter-pin, and was it there when you pulled the boat? If not, they can break after being bent a few times, and if it fell out the nut will loosen over time.

[hal2814]

Thanks for the tip. Cotter pin is in good shape. It’s the nylock style nut, not the castle style. The cotter pin is too far back to stop the nut from spinning. It would just keep it from falling all the way off.

[charlesml3]

No, the prop being a little loose on the shaft will not cause this kind of vibration. When you go forward, the prop will push forward onto the shaft anyway. Almost for sure you have a bent flute on that prop. They can be hard to spot sometimes.

-Charles

[hal2814]

So I just did a water test. I tested with my old prop (ACME 1235) and the one I had on at the time of the incident (ACME 2079) and they both ran fine after pretty thorough lake trials. I agree with Charles that this should not cause that kind of vibration so I’m at a loss. It wasn’t some minor thing. It was a violent shudder. I think my next move is to re-lap the 2079 and install it with a new prop nut, cotter pin, and key. I’m also open to any other ideas.

[charlesml3]

So I just did a water test. I tested with my old prop (ACME 1235) and the one I had on at the time of the incident (ACME 2079) and they both ran fine after pretty thorough lake trials. I agree with Charles that this should not cause that kind of vibration so I’m at a loss. It wasn’t some minor thing. It was a violent shudder. I think my next move is to re-lap the 2079 and install it with a new prop nut, cotter pin, and key. I’m also open to any other ideas.

If they're both fine now then the most likely explanation is a piece of rope or something got caught on the prop. When you got back to the dock you probably went into reverse to slow and that set it loose from the prop.

And as far as lapping the prop on the shaft goes.... I'm not convinced this does anything at all besides look good and possibly make people feel better about it. I know the factory doesn't do this and neither do the dealers. It certainly doesn't hurt, but I'm not convinced it makes anything better either.

-Charles