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We have just had our stern gear replaced, the prop because I'd taken a chunk out of it due to hitting something solid and the shaft, cutlass bearing and dripless stern gland (Volvo stuffing box) due to wear. On leaving the dock and heading up the canal we now have a whine in forward gear only from tickover to just over 1000 rpm. 

 

With the previous propellor there was about one finger of shaft exposed between the prop and hull. I can now get two fingers in easily. This gives less than an inch clearance between the end of the shaft and the leading edge of the rudder blade. Could this be the cause? 

 

It's a Vetus prop, shaft and bearing with a Vetus badged Centaflex coupling. Just the gland seal is Volvo Penta. 

Edited by pearley

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Could be prop singing. Usually more of a screech than a whine and over quite a narrow rev range.

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At certain blade speeds you can get a "chirp" which is more of an off board noise, easier to hear from outside or in a nearby boat. This is dependant on the blade shape and edges and the position relevant to the rudder and hull.

 

A "whine" after repair because of a damage event would suggest gearbox or stern gland to me. Particularly if noticeable on board. Did they hammer the blade off the shaft?

 

So what precisely is the noise like?

Edited by Boater Sam
smellings

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I think the words "with the previous propeller" are significant. I bet the previous one was more substantial than the replacement. I and others have complained about whining propellers. It is annoying if you suffer from it. In our case it was impossible to ignore. Sometimes filing the edges does the trick

 

How far the shaft extends beyond the stern gland seems to affect things too.

 

Our noise didn't go away until we replaced the propeller.     

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2 hours ago, Boater Sam said:

At certain blade speeds you can get a "chirp" which is more of an off board noise, easier to hear from outside or in a nearby boat. This is dependant on the blade shape and edges and the position relevant to the rudder and hull.

 

A "whine" after repair because of a damage event would suggest gearbox or stern gland to me. Particularly if noticeable on board. Did they hammer the blade off the shaft?

 

So what precisely is the noise like?

It's a whine increasing in intensity until just over 1000 revs when it disappears. Stern gland is a dripless Volvo one and was replaced. Bearing was replaced. 

2 hours ago, Cheshire cat said:

I think the words "with the previous propeller" are significant. I bet the previous one was more substantial than the replacement. I and others have complained about whining propellers. It is annoying if you suffer from it. In our case it was impossible to ignore. Sometimes filing the edges does the trick

 

How far the shaft extends beyond the stern gland seems to affect things too.

 

Our noise didn't go away until we replaced the propeller.     

Engineer has been back and tapped shaft further into the coupling. Whine when in gear whilst still tied up seems to have gone now. We'll see/hear properly when we move tomorrow. 

2 hours ago, Boater Sam said:

Cheap prop used?  Happens a lot.  Go see Crowthers for a proper one.

Old and new props are both Vetus

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I would guess that this is prop singing, usual cure is apparently filing the edges to sharpen them but when I had a singing prop it just went away eventually, I think that when the prop grew a coating of what is probably metal deposits from the anodes and hull it changed it just that little bit. I try not to think about that too much.

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8 hours ago, Bee said:

I would guess that this is prop singing, usual cure is apparently filing the edges to sharpen them but when I had a singing prop it just went away eventually, I think that when the prop grew a coating of what is probably metal deposits from the anodes and hull it changed it just that little bit. I try not to think about that too much.

I suspect a few nicks from stones altered the vibration frequency of one or two blades a little.

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I have been sent a pdf  from Vetus showing what to do. Very much the same as you. We'll have to live with it until our next dry docking by which time it might well have gone or changed.

Edited by pearley

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2 hours ago, Scholar Gypsy said:

This is what I did - involving some filing, as described on an earlier post here (link is in the blog). Worked a treat.

https://nbsg.wordpress.com/2016/11/05/blacking-and-no-more-singing/

When you say "an angle of 30 degrees", does that mean 30 deg to the edge of the blade and 60 deg to the face?

 

Edited by Señor Chris

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17 minutes ago, Señor Chris said:

When you say "an angle of 30 degrees", does that mean 30 deg to the edge of the blade and 60 deg to the face?

 

No, a 30 degree angle between the file and the face of the blade. I kept going until the tip had reduced in thickness by about 50%. if you enlarge the photo in my blog you can see the size of the filed area - the shiny bit, about 2mm. I reckon I halved the thickness of the tip from 2mm to 1mm  (sin (30deg) = 0.5). 

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12 minutes ago, Scholar Gypsy said:

No, a 30 degree angle between the file and the face of the blade. I kept going until the tip had reduced in thickness by about 50%. if you enlarge the photo in my blog you can see the size of the filed area - the shiny bit, about 2mm. I reckon I halved the thickness of the tip from 2mm to 1mm  (sin (30deg) = 0.5). 

OK, thanks - I'm out of the water at the moment so I'll give it a go.

 

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2 hours ago, pearley said:

I have been sent a pdf  from Vetus showing what to do. Very much the same as you. We'll have to live with it until our next dry docking by which time it might well have gone or changed.

People have been known to do it underwater.

 

Filing the prop, that is.

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21 hours ago, BruceinSanity said:

People have been known to do it underwater.

 

Filing the prop, that is.

I know and I've filed dings myself but the amount Vetus and Simon talk about is quite considerable and fairly specific. To do it properly would need fairly clear water, at least enough to see one blade at a time, not something easily found around Birmingham. 

 

I'll see how it is after a stones, etc have been kicked up and taken their toll on the prop. 

singing prop info.pdf

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