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AuthorMessage
mmarvel
mmarvel

Posted: Mon Aug 12, 2013 12:57pm

Post Subject: Singing prop

Hi, i have a 45 narrowboat with a 35hp Beta marine engine. I have become increasingly aware of a whining noise at certain revs., but not at others. It has be suggested to be prop whine caused by the blunting of the prop edges. I am soon to have the boat out of the water and want to cure this very annoying noise. Am told that sharpening the leading/trailing edges will cure it?? Would welcome your advise. Many thanks

Tony-B
Tony-B

Posted: Mon Aug 12, 2013 2:08pm

Post Subject: Singing prop

Often sharpening the trailing edge is recommended but other experts recommend rounding the leading edge. You should certainly remove and knicks and burs from the blades. It is claimed that a sharp leading edge cases the blade to vibrate and this resonates throughout the prop. If you can alter the resonation frequency of each blade so they do not excite the other blades you might effect a cure. Using a F type adjustable spanner on each blade tip, through the weed hatch, to put a small kink in one or more blades may have the effect you want. I am not going to recommend that you grind the blade yourself but certainly talk to whoever takes the boat out of the water. This is a common problem. One other point. The anti-cavitation plate that hangs down from many weed hatches have been known to vibrate and create a noise against the hatch trunk. Try temporally replacing the weed hatch with a stout piece of plywood to see it the noise stops. If it does try either griding the plate edges down to give greater clearance or stiffen whatever holds the plate to the weed hatch cover. I often feel that curing such things is a bit like black magic. Tony Brooks

Puppies
Puppies

Posted: Fri Aug 23, 2013 6:36pm

Post Subject: Singing prop

We had a singing prop too from 1100to1600rpm. We had to change the propeller to an Axiom which cost some money but did the job. Visit their website for a last resort.

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