Boat vibration

[rgriffiths]

We have a Colecraft with a Beta 1505 engine. The engine was recently removed so that new engine mounts could be put on. A new drive plate was fitted at the same time. All is clean and tidy and the engine runs very nicely.

 

However ... there is a general vibration across the whole boat with the engine running, both when stationary or when cruising. Cups rattle, the kitchen towel roll unravels, walls vibrate (gently push the bathroom wall with your finger and it stops but it is a very annoying noise the rest of the time).

 

Is this something anyone else has experienced and managed to resolve? Could it be that the engine is held too tightly on the new mounts? Clutching at straws a little and perhaps something I have to live with but it is very irritating.

Edited September 19, 2016 by rgriffiths

[Tiggs]

And it was not like this before the engine was removed?

 

Why did you want new mounts? what was wrong with the old ones?

 

There could be a lot of things causing vibrations but engine misalignment is often the issue - however you say that vibration is bad when stationary - so I would question the mounts - are they the correct sort for that engine?

Edited September 19, 2016 by Tiggs

[rgriffiths]

The mounts were replaced following the surveyors report. We then bought the boat. The mounts have since been checked since by the engineer that fitted them (I called him out as I thought it was not right) and another engineer subsequently (albeit a 5 min poke around and a sniff). The alignment was checked too. The mounts are the right ones so I am told, and the engine is sitting reasonably low on them, which I have also been told is good.

 

But 2 months on it is getting really annoying.

Edited September 19, 2016 by rgriffiths

[system 4-50]

Is this relevant (from the BetaMarine manual):

The pillar stud on the flexible mount is secured into position by the lower locknut, do not forget to tighten this. Also ensure that the stud is not screwed too far through the mounting body so that it can touch the bearer. This will cause vibration and knocking noises which are very hard to find! If the flexible mounting is too far offset then the loading on the flexible mounting will cause premature failure, modifications are needed.

[Tiggs]

system 4-50 has an idea that appears to have been a issue a few times before; other instances talk about knocking, but if it is too far wrong then it won't knock it will transmit vibration - so well worth investigating.

 

The second mechanic appeared to think the vibration you had was "normal". In fact there will always be some, buy unwind of kitchen roll suggests it is much worse than normal.

[ditchcrawler]

How about exhaust

[Tony Dunkley]

We have a Colecraft with a Beta 1505 engine. The engine was recently removed so that new engine mounts could be put on. A new drive plate was fitted at the same time. All is clean and tidy and the engine runs very nicely.

 

However ... there is a general vibration across the whole boat with the engine running, both when stationary or when cruising. Cups rattle, the kitchen towel roll unravels, walls vibrate (gently push the bathroom wall with your finger and it stops but it is a very annoying noise the rest of the time).

 

Is this something anyone else has experienced and managed to resolve? Could it be that the engine is held too tightly on the new mounts? Clutching at straws a little and perhaps something I have to live with but it is very irritating.

 

You will get the sort of vibration you describe if the mounts are not adjusted correctly so as to share the weight of the engine, and the dynamic loads when running, equally between all four mounts.

[Chewbacka]

We have a Colecraft with a Beta 1505 engine. The engine was recently removed so that new engine mounts could be put on. A new drive plate was fitted at the same time. All is clean and tidy and the engine runs very nicely.

 

However ... there is a general vibration across the whole boat with the engine running, both when stationary or when cruising. Cups rattle, the kitchen towel roll unravels, walls vibrate (gently push the bathroom wall with your finger and it stops but it is a very annoying noise the rest of the time).

 

Is this something anyone else has experienced and managed to resolve? Could it be that the engine is held too tightly on the new mounts? Clutching at straws a little and perhaps something I have to live with but it is very irritating.

If you mean 'all the nasty vibration' stops when you push the bathroom wall then I think you have a resonance problem.

You can check this by increasing the engine revs to say 1100rpm and the vibration should greatly reduce if it is resonance.

 

If it is resonance then you can improve/fix this by changing the resonant frequency of the wall. To do this either stiffen the wall with a batten or try fixing a big weight (guessing at 2 or 3 kg) in the centre of the wall. If this works you can then find a more visually pleasing method.

[bizzard]

 

You will get the sort of vibration you describe if the mounts are not adjusted correctly so as to share the weight of the engine, and the dynamic loads when running, equally between all four mounts.

Indeedee.

[dor]

Engine not set up properly on the mounts is my guess. A lot of canal "engineers" (I use the term with caution) just do not know how to set them up properly. Most common mistake that will give rise to excessive vibration is the engine rocking on the diagonal. Front and rear mountings seem ok and lined up, but engine can still rock.

[bizzard]

Engine not set up properly on the mounts is my guess. A lot of canal "engineers" (I use the term with caution) just do not know how to set them up properly. Most common mistake that will give rise to excessive vibration is the engine rocking on the diagonal. Front and rear mountings seem ok and lined up, but engine can still rock.

Indeedee again. In my opinion most of the inland waterways boatyard fitters need to go to proper old fashioned coastal working boat yards to learn the skills properly, I'd be inclined to avoid posh and flashy coastal marinas though for having work done.

[rgriffiths]

Thanks all. The bathroom wall is just an example and I have tried adding a positioned coat rack to no avail. The vibration of the boat goes at about 1500 rpm. There is definately a resonance issue - I can feel it in my ears. As I say, very annoying.

[Chewbacka]

Thanks all. The bathroom wall is just an example and I have tried adding a positioned coat rack to no avail. The vibration of the boat goes at about 1500 rpm. There is definately a resonance issue - I can feel it in my ears. As I say, very annoying.

So first off see if you can reduce the vibrational energy going into the hull by tuning the mounts as already suggested by others, then think about damping any surfaces that resonate at idle or cruising engine speed.