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Post by callisto on May 31, 2013 13:43:59 GMT
I have a SO 40.3 with a fixed 3 bladed prop. When sailing and locked in reverse the prop "sings" between 4.7 and 6 knts. Does anyone else have experience of this and any suggestions as to how to stop it??
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Post by so40gtb on Jun 6, 2013 2:04:40 GMT
A bit more info would help - have you taken a look at the prop shaft when this happens? Does it rotate? I assume that your prop is "conventional" fixed, correct?
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Post by callisto on Jun 10, 2013 15:45:43 GMT
apologies for not replying sooner (been sailing for a week)
It is the conventional fixed 3 bladed prop and I lock the in reverse when sailing. The first time it happended I did check that it was not rotating but that'swhen it first happended - I pretty sure it does not move/rotate.
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Post by j on Jun 11, 2013 2:48:10 GMT
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Post by callisto on Jun 11, 2013 14:29:11 GMT
To stop it turning when sailing !
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Post by callisto on Jun 11, 2013 14:33:48 GMT
Sorry - replied to question before reading link - very interesting - will have to consider some kind of shaft lock as you get a drone from ther gear box when sailing as well but thanks for the link - well noted..
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Post by tedp on Jun 13, 2013 8:31:11 GMT
The manual on my SO32 advises to lock the prop in reverse as well when sailing. This is normal practice and it has been discussed before on this forum.
My boat has a two blade prop and occasionally I also experience the 'singing' you refer to. If it does I unlock it for a moment, then re-lock it and usually the singing stops.
I expect it is a vibration of one or more prop blades acting like a tuning fork due to the water flowing across the sharp edge. If you strike a prop blade with a tool when the boat is on the hard, it will give off a similar tone height.
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Post by callisto on Jun 14, 2013 9:18:20 GMT
Thanks for that. When I lock the prop i need to start the engine or almost stop the boat to engage neutral so to date have just put up with the noise until I either slow or speed up which stops it.
I am considering a folding prop but this will still require to engage reverse and back to all those other issues.....
Thanks again
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