Vibration from weed weed hatch

[PeterF]

9 minutes ago, umpire111 said:

What did he do, file the prop?

Yep.

[GUMPY]

On 20/07/2021 at 15:54, umpire111 said:

It’s not a vibration sound, 99% sure it’s turbulence or cavitation 

 

Loddon suffers from "ventilation" where air is sucked in from the edge of the counter.

Only happens when tramping on a bit, I believe it's caused by being over propped, (1500rpm is over 5mph in deep water) and there is not enough water available to satisfy the prop so it drags air in.

Never really noticeable when travelling at canal speeds.

It sounds like blodylaboop and bubbles of air appear in the propwash. Is this similar?

After living with it for nine years I might get the pitch reduced on the prop next year😱

 

But then I might not.

[umpire111]

4 minutes ago, Loddon said:

 

Loddon suffers from "ventilation" where air is sucked in from the edge of the counter.

Only happens when tramping on a bit, I believe it's caused by being over propped, (1500rpm is over 5mph in deep water) and there is not enough water available to satisfy the prop so it drags air in.

Never really noticeable when travelling at canal speeds.

It sounds like blodylaboop and bubbles of air appear in the propwash. Is this similar?

After living with it for nine years I might get the pitch reduced on the prop next year😱

 

But then I might not.

It’s something like that but mine is quiet in deeper water, not a sound on the Thames, only happens in shallower canals.

[ditchcrawler]

1 hour ago, umpire111 said:

It’s something like that but mine is quiet in deeper water, not a sound on the Thames, only happens in shallower canals.

Mine shudders all over the place when I power out of an empty narrow lock, maybe I should leave at tickover?

[umpire111]

Well strange, back to the boat for a couple of weeks sailing, out for one day and still that annoying noise. Then I replaced stern gland packing….not a noise since! This is first time I ever changed packing, I removed two untouched rings from the gland, but there was not a sign of any debris for the one at the business end, is that usual? I put three new rings of packing in. Could that noise have been from stern gland? I’m very confused.

[Bee]

Well I never thought of that or even heard of it before but I suppose that if the shaft is not nicely supported in the packing it could indeed wobble a bit. Would have thought there would be a fair bit of water coming in but machinery can do odd things.

[dmr]

That's interesting. Assuming the stern gland is now tighter you will have a tiny bit more load on the engine, and any couplings will also have a bit more pre-load.

If the problem is a resonance of any sort you will also have increased the damping.

You could slightly slacken the stern gland nuts and see if the problem returns but probably better just to carry on and keep your fingers crossed.

 

If the problem does return then do a few turns on the greaser and see if that gives a short term fix.

[PeterF]

5 hours ago, umpire111 said:

Well strange, back to the boat for a couple of weeks sailing, out for one day and still that annoying noise. Then I replaced stern gland packing….not a noise since! 

 

Well now, we have been out these last few weeks and ours keeps making the noise which I have described before when accelerating and as noted also have a new Colecraft shell. Perhaps I will go ahead and repack the gland, I have done it in the water on my old boat so know how to do it.

[umpire111]

6 minutes ago, PeterF said:

 

Well now, we have been out these last few weeks and ours keeps making the noise which I have described before when accelerating and as noted also have a new Colecraft shell. Perhaps I will go ahead and repack the gland, I have done it in the water on my old boat so know how to do it.

Look forward to your after comments

[blackrose]

I haven't read every post on this thread so you may have already considered this, but I'd have thought that the noise and vibration could be coming from almost anywhere at the back of the boat. It could even be a mooring stake or hammer laying on the uxter plate or deckboards vibrating on supporting gutters.

 

It's quite difficult to identify exactly where vibrations are emanating from, but if you haven't done it already I'd be removing or isolating every loose object in the engine space and laying deckboards on bits of carpet or underlay to make sure they're not the culprits before thinking about modifying the weedhatch, prop or stern gland.

[umpire111]

1 hour ago, blackrose said:

I haven't read every post on this thread so you may have already considered this, but I'd have thought that the noise and vibration could be coming from almost anywhere at the back of the boat. It could even be a mooring stake or hammer laying on the uxter plate or deckboards vibrating on supporting gutters.

 

It's quite difficult to identify exactly where vibrations are emanating from, but if you haven't done it already I'd be removing or isolating every loose object in the engine space and laying deckboards on bits of carpet or underlay to make sure they're not the culprits before thinking about modifying the weedhatch, prop or stern gland.

Did all that some months ago on day 1, Tx