Issues After Prop Shaft Removal

[Rhian]

We recently had the rubber cutlass bearing replaced on our Beneteau 473, which involved the removal of the prop shaft and rudder.

Now, back in the water, we have noticed at very low revs there is a high pitched squealing noise and a lot of vibration. Also, when sailing above 6.5 knots, we get the same noise and if we lock the prop we get a resonance through the shaft which is also very loud.

If anyone has any comments, advice or suggestions, we would be grateful as at the moment, it is ruining our sailing and we are worried about further damage to the engine, gearbox etc.

Many Thanks

[donradcliffe]

It sounds like another case of having the yard work on your boat when you are not there.

I'm assuming the cutlass is in a strut, so its not likely that the bearing is running dry--the squeal could be the outside of the bearing turning in its holder. It could be they used the wrong size bearing.

Noise when you lock the shaft is a total mystery.

[Vasco]

Originally Posted by donradcliffe

It sounds like another case of having the yard work on your boat when you are not there.

I'm assuming the cutlass is in a strut, so its not likely that the bearing is running dry--the squeal could be the outside of the bearing turning in its holder. It could be they used the wrong size bearing.

Noise when you lock the shaft is a total mystery.

The B473 does not have a strut. It should have a through hull and water cooling to the shaft log. Perhaps there's a problem with this.

[Rhian]

Thanks for your responses - we will keep investigating!

[model 10]

Originally Posted by Rhian

We recently had the rubber cutlass bearing replaced on our Beneteau 473, which involved the removal of the prop shaft and rudder.

Now, back in the water, we have noticed at very low revs there is a high pitched squealing noise and a lot of vibration. Also, when sailing above 6.5 knots, we get the same noise and if we lock the prop we get a resonance through the shaft which is also very loud.

If anyone has any comments, advice or suggestions, we would be grateful as at the moment, it is ruining our sailing and we are worried about further damage to the engine, gearbox etc.

Many Thanks

Do you have a automatic propeller? If one blade was out of whack or stuck, it might cause the cutlass to squeal when turning because of the weird load on the shaft and it would cause a turbulence when stopped which could vibrate the prop shaft. You guy's have skinny prop shafts right?

[Rhian]

The prop shaft is 30mm but we don't have an automatic prop. It now seems that the engine may be slightly out of alignment with the shaft, causing it to pinch the new cutlass bearing. We have been told it might improve with a few more hours motoring, otherwise we might have to re-align the engine a touch.

[DefinitelyMe]

Had this problem before (minus the weird noise with the prop locked....... not sure what that is!). Turned out to be an alignment issue. Can you turn the prop shaft by hand (when it's not in gear!)? If so, and if this is indeed the issue as you say then it's probably not too bad. My noise abated pretty quickly; maybe 10 hours of motoring. Or you can re-align the engine with a couple of feeler-guages.

[Vasco]

Originally Posted by Rhian

The prop shaft is 30mm but we don't have an automatic prop. It now seems that the engine may be slightly out of alignment with the shaft, causing it to pinch the new cutlass bearing. We have been told it might improve with a few more hours motoring, otherwise we might have to re-align the engine a touch.

This sort of problem does not usually correct itself. If it's an engine alignment problem it should be corrected asap.

[Rhian]

Yes, we can turn the prop shaft by hand, so fingers crossed it will be OK :-)

[Boatyarddog]

Maybe the prop shaft is touching the packing box, rubbing on it a bit?


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[Snowpetrel]

Originally Posted by Vasco

The B473 does not have a strut. It should have a through hull and water cooling to the shaft log. Perhaps there's a problem with this.

+1 Good call, I assume you have checked the stern tube is full of water and the shaft seal has been bled? The water injection point /bleed line might have blocked up since the last slipping.

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[Suijin]

Originally Posted by Rhian

Now, back in the water, we have noticed at very low revs there is a high pitched squealing noise and a lot of vibration. Also, when sailing above 6.5 knots, we get the same noise and if we lock the prop we get a resonance through the shaft which is also very loud.

Just to clarify, you get the same noise, a high pitched squealing, when under sail and the shaft is locked in gear and not turning? Or you just get resonance?

If you're (aside from the resonance) getting the same noise at low RPMs and when the shaft is locked, then it stands to reason that they have the same cause, and it also stands to reason that it has nothing to do with the seal or with alignment. Neither would be the cause if the shaft is not turning.

Are you certain you don't have a feathering prop? If you have a max prop then there is an excellent chance that they took the prop off when they removed the shaft, and to take it off you have to take it apart. There's a remarkably good chance that when they put it together they did not get the pitch of all the blades the same. That's pretty much the only thing I can think of that could be the cause, although the high pitched squeal when underway with the shaft not turning is pretty baffling.