Propeller whine - why?

[Bojangles]

I've just launched a new 55' N/b with a Barrus 40hp Shire engine with PRM box and propeller as recommended by Barrus. Between 1100 and 1300 revs the propeller whines, or I think some say 'sings'. Below and above these revs there's just the normal prop wash noise.

 

Currently I 'm cruising at 1000 revs, which is fine. But if I want a bit more power I get this horrible whine.

 

Can anybody tell what generally causes this noise and hopefully how it can be stopped.

Edited June 1, 2008 by Bojangles

[alan_fincher]

Have you seen this previous thread ?

 

http://www.canalworld.net/forums/index.php...ging++propellor

[alan_fincher]

There appear to be two identical threads on this.

 

Mods - can you please remove one of them! Ta.

[Bojangles]

Have you seen this previous thread ?

 

http://www.canalworld.net/forums/index.php...ging++propellor

 

Thanks Alan for your help and the link which is exactly the prob I'm having

 

When I do searches I never seem to put in the correct search criteria and therefore I hadn't seen the info .

 

Cheers Jack

[Yoda]

I've just launched a new 55' N/b with a Barrus 40hp Shire engine with PRM box and propeller as recommended by Barrus. Between 1100 and 1300 revs the propeller whines, or I think some say 'sings'. Below and above these revs there's just the normal prop wash noise.

 

Currently I 'm cruising at 1000 revs, which is fine. But if I want a bit more power I get this horrible whine.

 

Can anybody tell what generally causes this noise and hopefully how it can be stopped.

 

Has it got a dent in it?

[Dominic M]

I think I posted this originally in the wrong section - ooops

 

I've just launched a new 55' N/b with a Barrus 40hp Shire engine with PRM box and propeller as recommended by Barrus. Between 1100 and 1300 revs the propeller whines, or I think some say 'sings'. Below and above these revs there's just the normal prop wash noise.

 

Currently I 'm cruising at 1000 revs, which is fine. But if I want a bit more power I get this horrible whine.

 

Can anybody tell what generally causes this noise and hopefully how it can be stopped.

Change the prop size. It's common for a whine to happen at certain rpm - but very annoying when it is at normal cruising speed. Changing the prop to one with a different pitch or size will cure it normally.

[bottle]

Three previous mentions of "singing prop" not read them but they may help.

 

http://www.canalworld.net/forums/index.php...ging+prop\

 

http://www.canalworld.net/forums/index.php...ging+prop\

 

http://www.canalworld.net/forums/index.php...ging+prop\

 

The wonders of 'search'

[bargeeboy]

I've just launched a new 55' N/b with a Barrus 40hp Shire engine with PRM box and propeller as recommended by Barrus. Between 1100 and 1300 revs the propeller whines, or I think some say 'sings'. Below and above these revs there's just the normal prop wash noise.

 

Currently I 'm cruising at 1000 revs, which is fine. But if I want a bit more power I get this horrible whine.

 

Can anybody tell what generally causes this noise and hopefully how it can be stopped.

 

We fit 40 hp Shire in our NarrowCraft boats and expirienced this a few years ago whilst perfecting our design.

 

I would suggest that the gap around the weedhatch baffle is not such a good fit. Dock the boat and check you might need to lengthen the baffle supports or make a new one that fits snug.

 

You might also have the blade too close to the counter. In this case change the 18x10 blade to a 17x12 .

Edited June 2, 2008 by bargeeboy

[Timleech]

I've just launched a new 55' N/b with a Barrus 40hp Shire engine with PRM box and propeller as recommended by Barrus. Between 1100 and 1300 revs the propeller whines, or I think some say 'sings'. Below and above these revs there's just the normal prop wash noise.

 

Currently I 'm cruising at 1000 revs, which is fine. But if I want a bit more power I get this horrible whine.

 

Can anybody tell what generally causes this noise and hopefully how it can be stopped.

 

The cause can sometimes be quite elusive.

I fitted new prop shaft & bearing to a boat a couple of years ago, all identical, the owner had a bad whine problem afterwards which hadn't been there before. The one thing which had changed was that I'd found the engine had been way out of line, one of the reasons why the sterngear had worn. The misalignment had been putting a vertical load on the bearings which had stopped the shaft oscillating and thus damped the whine which had probably been there potentially all along.

There are various things which can be tried, basically anything which introduces a change.

Altering shaft projection from the bearing is often an easy one. I've had good results on a couple of occasions from sharpening the leading edges of the propellor blades. I've also heard from people for whom the opposite, blunting the blades, has worked.

I was once told of two identical ships of which one had this problem. At one stage both were in dry-dock at the same time. As all other efforts had failed, it was decided to swap propellors between the two ships, after which neither had the problem.

 

Tim

[Foxglove]

I've been unlucky enough to have a singing prop on the present boat and the last one . It was cured both times by taking the prop off and having experts put an anti-singing edge on . It 's basically a chamfer of around 20 degrees ground on the suction side of the blade tips . Diagram and explanation here , scroll to the bottom of the page http://www.olds.com.au/marine/terminology.html .

 

If you are happy with the size of your prop this solution is preferable and cheaper than buying a new prop of a different size . I managed to get my prop off and back on again through the weedhatch but it would be better to do it in drydock if you can put up with the noise until the boat's due for blacking .

 

With sympathy ,

 

Duncan

[NB Alnwick]

There appear to be two identical threads on this.

 

Mods - can you please remove one of them! Ta.

 

Threads merged and moved to 'Boating > General Boating' - I will remove any duplicated or surplus responses.

 

Best wishes,

Graham

[Bojangles]

To all of you that responded thankyou very much for your helpful replies. I feel we're now in with a chance of silencing the singing.

 

Jack