Singing Prop Any cure??

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H4B

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Reported on this forum before, a whine which comes in when shaft locked and sailing over 6 knots. I fitted a new shaft and replaced a sloppy cutlass bearing but still have whine albeit at a slightly different frequency.After 5 years its beginning to annoy me.
So, does any body have a cure ,short of a new prop. Would obviously like a new three bladed folder but got a quote and had to sit down.!! Any suggestions gratefully received.
Thanks.
 
I have been told (via a very experienced marine engineer) that a singing prop can be cured by.... a) if the edges are sharp, smoothing them off a little or b) if the edges are blunt, filing them a little sharper.

I don't have practical experience of this technique, but it may be worth exploring .

regards... Gubbo
 
Could it be that the prop is rotating with the motion of the boat through the water. The noise being from the bearings and other odds and ends as the shaft rotates. Try putting the thing in gear, this will stop the prop but will slow the boat too.
 
It only sings when its locked. The whine stops when prop left to trail with the associated trundling noises.
 
[ QUOTE ]
I had my singing prop fixed by T Norris marine.They did it while I waited cost about £25.

Martin

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Do you know what they did to it.? The edge filing sounds plausible but I would have to put the boat on the slip for a tide and would want to be sure of what to do .
Thanks Howard
 
The singing is resonance, and to stop it one has to change the resonant frequency of the assembly. A very cheap quick trick could be trying a shaft anode. This may at least help in identifying what is actually singing, it may be the shaft or it may be the prop.

The cheery side is that it does mean that it is unlikely there are casting failures in your prop.

PS reprofiling props to stop them singing is a black art, thoughm if there are obvious defect smoothing them out is unlikely to make things worse
 
[ QUOTE ]
Could it be that the prop is rotating with the motion of the boat through the water. The noise being from the bearings and other odds and ends as the shaft rotates. Try putting the thing in gear, this will stop the prop but will slow the boat too.

[/ QUOTE ]

I remember there being big discussions on here about whether a boat was slowed or not by locking the shaft
 
[ QUOTE ]
The singing is resonance, and to stop it one has to change the resonant frequency of the assembly. A very cheap quick trick could be trying a shaft anode. This may at least help in identifying what is actually singing, it may be the shaft or it may be the prop.

The cheery side is that it does mean that it is unlikely there are casting failures in your prop.

[/ QUOTE ]

Having fitted a new shaft and cutlass bearing and the fact that it does not sing when trailed I am convinced its the prop, as you say resonating.

What are the arguments re trailing or locking the shaft. ?
 
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