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Engine seems to be getting louder


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Running my engine seems to be getting louder and louder. It's hard to be sure as it's gradual but I was having to shout to make myself heard today and I'm sure that's not normal. I installed a hospital silencer about 2 years ago and I remember the engine being really quiet. I don't think it's the exhaust though, it sounds like there is something vibrating or something loose. Could it be that my engine mounts are wearing out?

 

It seems to be louder when the engine is cold and as it warms up it gets quieter, and if I get the revs just so then it's quieter. Traveling at tickover is unpleasantly noisy.

 

My only thought is to spend some time in the engine hole with my torque wrench and beta 38 manual and make sure everything is tight.

 

Would appreciate any ideas or tips to try to find the source of the noise...

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Check the temperature of the stern gland after a run and look to see if the shaft is in the centre of the pusher. That is unless you have a flexible (Vetus) stern gland or a Aquadrive type shaft coupling.

 

If a mount or mounts have collapsed the shaft will be running hard down on the gland and transmitting a lot of vibrations from the engine and shaft to the gland and thus the hull.

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8 minutes ago, zenataomm said:

Louder in gear or same as in neutral?

 

It's loud in neutral as well as in gear.

 

3 hours ago, Tony Brooks said:

Check the temperature of the stern gland after a run and look to see if the shaft is in the centre of the pusher. That is unless you have a flexible (Vetus) stern gland or a Aquadrive type shaft coupling.

I'll check this tomorrow, thanks. What temperature is normal for the stern gland?

 

 

7 minutes ago, Machpoint005 said:

Stupid question: have the sealing strips dropped off the deck boards?


My boat has a steel hinged lid, never had any sealing strips. It's really more of a vibration sound.

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9 hours ago, jetzi said:

 

I'll check this tomorrow, thanks. What temperature is normal for the stern gland?

 

They are often slightly warm but should not be hot, there should be no discomfort if you hold your hand on it but the hotter it is the more friction is in the gland assembly.

  • Greenie 1
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Anything that could drop down on to the engine, I had a floor support drop on to the top of the engine and it sounded like the engine was about to explode.

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5 minutes ago, Mike Tee said:

Engine mounts OK?

Forgive the stupid question, but how would I know?

 

1 minute ago, Rob-M said:

Anything that could drop down on to the engine, I had a floor support drop on to the top of the engine and it sounded like the engine was about to explode.

I stand on top of the engine when entering and exiting the engine bay (very awkward to get in otherwise). Am I damaging something by doing this?

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4 minutes ago, jetzi said:

Forgive the stupid question, but how would I know?

 

I stand on top of the engine when entering and exiting the engine bay (very awkward to get in otherwise). Am I damaging something by doing this?

 

1. Lever between (say) the sump flange and pivoted on the engine bed close to each mount and push down on the free end, see how much the engine will lift. I would suggest 6mm would be the absolute maximum and 3mm may be better. Lets have others opinions.

 

Look for signs of rubber attacked by hydrocarbons - sticky black mess.

 

Check the shaft going into stern gland as I  described.

 

2. Depends on where you put your boot but standing on a cast metal rocker cover should not do any harm, I would not stand on an exhaust manifold that was cantilevered away from the head like a BMC one.

 

 

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Take some pictures of the engine mounts and post them here. We can then opine.  You may get asked for detail or close ups of a possibly dodgy one.

 

N

 

PS.

Sucking of teeth and muttering are currently subject to COVID social distancing requirements.

Edited by BEngo
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When the rubber lump in engine mounts wears or rots it can make metal to metal contact = noise.  Engines without oil or water also get noisy but they don't often last very long  

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Maybe the engine idle speed has dropped off a little and the engine just needs speeding up a bit. This can happen over a period of time as things like the pump and governor speeder springs can stretch. Once the idle speed has dropped of just a little it can introduce vibration and rough running.

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4 hours ago, jetzi said:

Forgive the stupid question, but how would I know?

 

I stand on top of the engine when entering and exiting the engine bay (very awkward to get in otherwise). Am I damaging something by doing this?

If you have a pressure release cap on top of the engine, these can be damaged by being stood on too often. You can also possibly damage the fuel.spill rails unless you take care to keep away from these every time.

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Here are photos of the mounts.

 

I can already see the problem. The nut on the port-fore engine mount has worked loose, and with a crowbar I am able to rock the engine diagonally quite far until it bumps against the engine bearers. On the other two mounts it only moves a couple of mm.

 

So I suppose I just need to tighten this bolt?

 

Any idea how tight they should be? I have a torque wrench.

 

 

 

EngineMountStbdFore.jpg.5d673e8f53508a49e7db8614d5d796e0.jpgEngineMountPortAft.jpg.6f9f61e1b7d73c1e7562c947e28b593d.jpgEngineMountStbdAft.jpg.86f4182c715c45b03e65806fd3c3b914.jpgEngineMountPortFore.jpg.26bf58ee0c4cbe43912d1aad2b627f72.jpg

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You do NOT wind the top nut down but the bottom nut up.

 

Take the top nut up half a turn, tighten the bottom nut with a spanner then tighten the top nut down again half a turn as long as it is tight, 50 ft/lbs will do.

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18 hours ago, jetzi said:

 

It's loud in neutral as well as in gear.

 

...My boat has a steel hinged lid, never had any sealing strips. It's really more of a vibration sound.

 

Ah! Has the lid become slightly deformed, either leaving a gap that wasn't there before, or so that part of the lid now fouls part of its aperture it didn't previously touch? Was it screwed down before, and isn't now? 

 

I'm not saying there isn't a new mechanical source inside the engine, but a change in the transmission path might make quite a difference to what you hear.

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Ignoring the loose nut (do as Tracy says) The top picture suggest degraded rubber by hydrocarbons oozing out of the mount while the second one seems to have a strange strip of rubber sticking out. I would not be a bit surprised if at least two mounts have gone soft or failed.

 

With studs and nuts that size I doubt you can overtighten the nuts with normal tools, in the garage we would say the torque setting is FT.

 

After tightening that nut and in an ideal world you would undo the flexible shaft coupling (unless it's an Aquadrive type) and check the shaft alignment but if the noise goes away when the nut is tight its probably near enough.

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Ah, that looks like the problem. Now the tricky bit. Check the two rear mounts and hopefully they will look as though they have not moved. Then as Tracy said, wind the bottom nut up till the whole thing comes up to the top nut, that should then be OK as the top nuts are Nylock and vibration proof. That should all be perfect.  There is a 'should' in that last bit. Keep an eye and ear out for noise, vibration and wear for a while just in case things have moved a bit. It took me ages to get my engine sitting straight, level and square on its mountings and nicely lined up to the shaft.

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That loose mount was definitely 90% of the problem. Sounds much better now. I do notice that the engine doesn't seem to hum perfectly consistently - every few seconds it either sounds like the revs briefly speed up for half a second or slow down for half a second. i don't know if this is related or if there is something else going on.

 

Also - it's hard to say - but I think the engine is getting louder the longer it runs for. I think perhaps the bottom nut of that mount is working loose. I am going to let it run for half an hour and then check. If it is working loose again, is there anything I can do to stop it??

 

 

 

3 hours ago, Tracy D'arth said:

You do NOT wind the top nut down but the bottom nut up.

Thanks i definitely would have done this the other way around if you hadn't said!

 

 

 

1 hour ago, Tony Brooks said:

The top picture suggest degraded rubber by hydrocarbons oozing out of the mount while the second one seems to have a strange strip of rubber sticking out. I would not be a bit surprised if at least two mounts have gone soft or failed.

It could be oil from the engine as well - it's really mucky in there at the moment - I need to spend some time cleaning and repainting the bilge soon.

 

If the mounts have gone soft, I take it that's a boatyard job with a mini crane to lift the engine?

 

2 hours ago, Bee said:

Ah, that looks like the problem. Now the tricky bit. Check the two rear mounts and hopefully they will look as though they have not moved. Then as Tracy said, wind the bottom nut up till the whole thing comes up to the top nut, that should then be OK as the top nuts are Nylock and vibration proof. That should all be perfect.  There is a 'should' in that last bit. Keep an eye and ear out for noise, vibration and wear for a while just in case things have moved a bit. It took me ages to get my engine sitting straight, level and square on its mountings and nicely lined up to the shaft.

 

I wound down the top nut a bit so it's probably not in exactly the right place... I am only running out of gear at the moment, I suppose putting it in gear, checking for vibration, balancing, rinse repeat is the only way to align it.

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2 minutes ago, jetzi said:

That loose mount was definitely 90% of the problem. Sounds much better now. I do notice that the engine doesn't seem to hum perfectly consistently - every few seconds it either sounds like the revs briefly speed up for half a second or slow down for half a second. i don't know if this is related or if there is something else going on.

 

Also - it's hard to say - but I think the engine is getting louder the longer it runs for. I think perhaps the bottom nut of that mount is working loose. I am going to let it run for half an hour and then check. If it is working loose again, is there anything I can do to stop it??

 

 

 

Thanks i definitely would have done this the other way around if you hadn't said!

 

 

 

It could be oil from the engine as well - it's really mucky in there at the moment - I need to spend some time cleaning and repainting the bilge soon.

 

If the mounts have gone soft, I take it that's a boatyard job with a mini crane to lift the engine?

 

 

I wound down the top nut a bit so it's probably not in exactly the right place... I am only running out of gear at the moment, I suppose putting it in gear, checking for vibration, balancing, rinse repeat is the only way to align it.

 

 

Red:  That sounds like surging and its not unusual for diesels to do that if the governor is either a crude design or maybe bait sticky. I would ignore it, especially as you are probably now hyper-aware.

 

Blue: If it is do it up even tighter but I doubt it is.

 

Last paragraph: if you have messed with the top nut then the alignment is now out and the diagonal loads are unbalanced. You can try by trial and error but it really needs the engine alignment checking but if those mounts have had it then it would be better to get it all done at once. If an engineer changes the mounts they should do the alignment as routine. The proper way is to free the shaft at the coupling and go through the alignment process.

  • Greenie 1
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Alignment is done with feeler gauges between the disconnected coupling halves unless you have a Python or Aqua drive, I doubt that you have the mechanical savvy to do it so I would get the mounts sorted by a marine engineer and ensure that he aligns it properly.  Its more of a knack than a skill. some are good at it, others,,,,,well.

You need to get all that oil sorted out too, it will wreck your new mounts. They will rot if oily.  Is it a leak or spillage?

Can you sent a pix of the coupling and shaft behind the gearbox?

 

 

Edited by Tracy D'arth
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