Quite engine but noisy drive or cavitation?

[andy3784]

I have had my narrow boat for some years but only recently had time to cruise any for distance. Whilst the engine noise is low the racket coming from the prop is now getting on my nerves. I think it might be cavitation. It is almost always present with only a few golden moments when it goes away for a brief period. How can I confirm the problem? Who can help me fix it? Any ideas? Oh for a quite life. I have no sound insulation under my cruiser stern which houses a Lombarini 1204 engine driving a 12" prop on my 45' boat.

[alan_fincher]

Hi, welcome!

 

Sorry to ask the obvious, but....

 

1) Has it always done this?

2) If "no", did it worsen slowly over time, or all come on at once?

3) Have you either had a good look at it on a slip, or by fumbling down the weed hatch, and are you sure there is no obvious damage to the prop, or bending of the shaft?

[Keeping Up]

To ask two more obvious questions:

 

Does it do this at all speeds, or only slow or only fast?

Is there any chance you could try and describe the noise? Does it whistle, is it a steady note or varying, does it pulsate, etc?

[andy3784]

Hi, welcome!

 

Sorry to ask the obvious, but....

 

1) Has it always done this?

2) If "no", did it worsen slowly over time, or all come on at once?

3) Have you either had a good look at it on a slip, or by fumbling down the weed hatch, and are you sure there is no obvious damage to the prop, or bending of the shaft?

It has happened all the time as far as I remember. With no previous experiece on a narrow boat I did not thing it an issue before.

There is nothing obvious on the prop as seen or felt through the weed hatch and the shaft looks ok.

The noise is a whoop,whoop, whoop at all speeds and is loud all through the boat.

[Yoda]

It has happened all the time as far as I remember. With no previous experiece on a narrow boat I did not thing it an issue before.

There is nothing obvious on the prop as seen or felt through the weed hatch and the shaft looks ok.

The noise is a whoop,whoop, whoop at all speeds and is loud all through the boat.

 

I would be surprised if this wasn't a bent prop.

[Smelly]

Might the prop be singing?

[andy3784]

Might the prop be singing?

 

 

I have posted a short video on which you can hear the sound although the relative volume v's the engine noise is louder in the flesh so to speak.

Unfortunately it could take 4 days for the video to be searchable on Youtube.

Hopefully If you go to Youtube.com and search Anonymus boat noise it should give a view of the boats wake and the offending sound.

thanks.

[RLWP]

I have posted a short video on which you can hear the sound although the relative volume v's the engine noise is louder in the flesh so to speak.

Unfortunately it could take 4 days for the video to be searchable on Youtube.

Hopefully If you go to Youtube.com and search Anonymus boat noise it should give a view of the boats wake and the offending sound.

thanks.

 

Can you not post a link to it?

 

Richard

[Ike]

[mykaskin]

If I am hearing what I think I'm hearing - we had the same problem with our prop - like a swishing sound? It may be the prop edges that aren't very good and causing cavitation around the tip of the prop. It steadily got better on ours as the blade wore down, but you might want to check with your hands that the blades are nicely shaped.

 

It could also be prop singing where resonant vibrations set up in the blades, all you can do is physically alter the prop shape/size but will effect performance, or replace with a new one of good quality.

 

Cheers,

 

Mike

[Yoda]

Having listened to the sound, I have decided that it is sticky water causing the problem.

[Timleech]

Could be that if your weedhatch lid has a false base (to improve water flow), it's not mounted sufficiently rigidly to the lid.

 

Does it, and if so how is it supported from the lid?

 

Tim

[steelaway]

Could be that if your weedhatch lid has a false base (to improve water flow), it's not mounted sufficiently rigidly to the lid.

 

Does it, and if so how is it supported from the lid?

 

Tim

 

 

I agree

I would suspect the weed hatch - it sounds too clancky to be prop singing

Loosen the weed hatch lid clamp and see if the noise changes

 

Alex