Jump to content

New engine mounts


NBDensie

Featured Posts

Recently we have had problems with engine vibration and gearbox "rattle" on our Isuzu 35 powered narrowboat.  The local boatyard found that the engine was mis-aligned and the mounts were in poor condition.  These were replaced.  This seems to have cured the vibration and rattling problems.

 

However, since then the engine has sounded louder and rougher.  Previously in deep water and low revs it "purred" not much louder than a car engine.  Walkers on the towpath had asked whether the boat was electric!  I cant see that happening now.

 

Do new mounts take a while to bed-in or should I look elsewhere for a solution? 

 

Note that we have Vetus water lubricated stern gear.  When new it did not leak at all but for some years, prior to the vibration problems, it has leaked about a tablespoon (15ml) of water a day.  Now it is leaking about 1litre/day, but only leaks when the prop is turning..  I was hoping that stopping the vibration would improve matters but it didnt.  Any links to the vibration or is it probably simply a matter of replacing the rubber seals?

 

Any thoughts much appreciated.

 

 

 

Link to comment
Share on other sites

Have you got a flexible coupling between the gearbox and stern seal? Aquadrive or something? There really should be as flexible mounts mean that the engine is moving just a bit all over the place. Alignment is really important on engines bolted direct to the bearers but much less so if there is a flexible coupling in the drive train. I've aligned a few engines and to be honest the first attempt is not always successful. (sometimes the second attempt isn't either but don't tell anybody)

Link to comment
Share on other sites

51 minutes ago, Bee said:

Have you got a flexible coupling between the gearbox and stern seal? Aquadrive or something? There really should be as flexible mounts mean that the engine is moving just a bit all over the place. Alignment is really important on engines bolted direct to the bearers but much less so if there is a flexible coupling in the drive train. I've aligned a few engines and to be honest the first attempt is not always successful. (sometimes the second attempt isn't either but don't tell anybody)

 

I agree about the alignment, but I think that stern gland is matched to a Cutless rubber shaft bearing, so a small degree of radial misalignment would be less critical.

 

Unlike Quattrodave, I wonder if the mounts are too soft and are allowing the shaft to bang against the stern tube, but I am sure the alinement should be rechecked.

 

I also suspect these Vetus stern gears are often matched with the hard plastic not very flexible type shaft coupling, which would not be my choice if there was no room for an Aquadrive.

Link to comment
Share on other sites

Thanks all for your comments.....

 

To answer one point:  I have greased the the stern gear with silicone grease through the grease point every 6months-year.

 

Based on your comments, my current thoughts on what to do next......

1) I need to get the boatyard to recheck that the new engine mounts are appropriate for my engine.  Engine mounts specifically stated to be suitable for an Isuzu 35 are available and look like my old ones.  The new mounts look different.

2) The engine alignment should be rechecked.

3) Whether a coupling is right for water lubricated stern gear ("cutlass bearing"?) and what sort is open to question.  Since the boat worked perfectly well without any stern gear leaks for 10 years with no coupling I think I wont pursue it.

4) I am not clear whether incorrect mounts could cause the increased noise levels and the change in tone. I now find the boat unpleasant to drive so need to do something.  Perhaps get the mount situation confirmed first.

5) No one has suggested getting the stern gear checked - perhaps the rubber shaft seals and the prop/bearings should be checked for wear? Hopefully this can be done withoiut taking the boat out of the water.

Link to comment
Share on other sites

Cutless bearing 

 

On the majority of narrowboats the shaft bearing just in front of the propeller is a brass/bronze sleeve and this is why it needs the greaser used very regularly. The front bearing is brass/bronze and is in effect the stern gland housing. The shaft is held rigidly, so can't really wave about.

 

On a Vetus stern gland the gland is mounted on rubber so it does not really support the shaft and the back bearing is a rubber tube with long slots/flutes in it house in a brass sleeve. The rubber allows the shaft a degree of freedom, so the shaft can wave about, especially at the front. The shaft is located by the Cutless rearing at the back and the engine coupling at the front. On these installations, it is vital that the shaft is wedged both vertically and horizontally right in the middle of the free movement before any attempt is made to align the engine to it. I just wonder it the yard just let the shaft drop and aligned to that rather than centralise it. If they did it may well bang on the tube with flexible mounts.

 

  • Greenie 1
Link to comment
Share on other sites

Just a thought. Increased noise and change of tone !! If, as is likely,  the engine was lifted to facilitate changing the mounts could the exhaust have been damaged? When I changed my mounts a couple of years ago I had to loosen the manifold to braided s/s connection. 

Link to comment
Share on other sites

2 hours ago, NBDensie said:

3) Whether a coupling is right for water lubricated stern gear ("cutlass bearing"?) and what sort is open to question.  Since the boat worked perfectly well without any stern gear leaks for 10 years with no coupling I think I wont pursue it.

 

I agree that as long as it properly aligned, the type of flexible coupling should not matter unless the engine is jumping about.

 

I think the shaft was not centralised so it is now pushing down on the seal and being a lip seal the lip will distort and probably leak.

 

 

 

Link to comment
Share on other sites

1 hour ago, NBDensie said:

Given the number of things that could go wrong I would be very grateful for any recommendations for someone in the Rugby or Braunston areas who could sort it all out

Try Mant Marine Services 07904031758. Can't remember his name but he does a fair amount of work in Cropredy. Not had any need of his services but heard several positive comments. 

Link to comment
Share on other sites

17 hours ago, Slim said:

Try Mant Marine Services 07904031758. Can't remember his name but he does a fair amount of work in Cropredy. Not had any need of his services but heard several positive comments. 

 

Clive Mant, excellent boat engineer but not cheap.

Link to comment
Share on other sites

When I 'shot' an engine mount, I bought a set of soft mounts as advised by a Chandlers, and had no end of problems with them. Eventually, I discovered my original mounts were R & D mounts, so I phoned them up. They asked for details such as Engine, gearbox, drive coupling and boat length and specified new mounts, with the front different to the back. They were neither cheap nor horrendously expensive, but did the job wonderfully. 

The lesson learnt is consult the experts and you get what you pay for.

  • Greenie 2
Link to comment
Share on other sites

42 minutes ago, Ex Brummie said:

When I 'shot' an engine mount, I bought a set of soft mounts as advised by a Chandlers, and had no end of problems with them. Eventually, I discovered my original mounts were R & D mounts, so I phoned them up. They asked for details such as Engine, gearbox, drive coupling and boat length and specified new mounts, with the front different to the back. They were neither cheap nor horrendously expensive, but did the job wonderfully. 

The lesson learnt is consult the experts and you get what you pay for.

 I agree completely with the principle.  Now all I need is an expert - any recommendations for one that covers the East Midlands?  Cost is not a major issue.  However implementation is beyond my experience.

Link to comment
Share on other sites

3 hours ago, NBDensie said:

 I agree completely with the principle.  Now all I need is an expert - any recommendations for one that covers the East Midlands?  Cost is not a major issue.  However implementation is beyond my experience.

Maybe the way to go would be to enquire and order from the manufacturer. Finding a local boatyard to fit them may not be too difficult. Lots of boatyards are too lazy, or generally disinclined to do such groundwork, but will pick up your pieces.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.