Broken engine mount

[Captain Fizz]

I have only had this boat a couple of months and decided to give the engine space bilge a proper scrub.

In doing so, I discovered a fractured front engine mounting.

It is a Thorneycroft engine and the rear mountings are made of at least 15mm thick steel whilst the fronts are only 10mm and of an inherently weak design. Time to get the welder out me thinks.

[Tony Brooks]

Which base engine? I am sure the BMCs used that sort of thickness for parts of the front mounting system (which varies from mariniser to mariniser).

 

Worth checking the shaft alignment (unless you have a two point flexible coupling) and idle speed because it could be excess vibrations that caused it.

[RLWP]

Most of the weight of the engine and gearbox is on the rear mounts, which is why the front mounts are often thinner than the rear ones

 

As well as Tony's list, check your flexible engine mounts. If one or more has worn out it could be transmitting lots of unnecessary forces into the bracketry

 

Richard

[Captain Fizz]

Hi Tony,

It's a Mitsubishi based unit. Having a closer look at the mounting back at my workshop, it has been made from an ancient piece of steel from the scrap box which is just too brittle. It sheared just where the webbing ended and whoever made it had had a couple of goes at getting the holes in the correct place.

All in all, destined to fail at some point.

I shall check shaft alignment when I refit though just to make sure. Tick over is at 750rpm and pretty smooth.

I will replace both front mounts with a slightly chunkier design.

Thanks for your observations Richard. Crossed with my post.

 

Simon.