Engine mount position.

[Lon nan Gruagach]

Ha very funny. Can't move the pump Dougal. Tried a bigger stud but the rear mount same side braket snapped, just moved the problem. Not sure what you mean 'flexible coupling' on top

My thought is that the long stud and rigid fixing to the engine is bending the stud.
Something like https://www.merlinmotorsport.co.uk/p/misab-anti-vibration-rubber-mounting-washers-csa005

where the stud is nutted to the engine.
Maybe the rubber sandwich will provide enough give.

 

[Plum]

My thought is that the long stud and rigid fixing to the engine is bending the stud.
Something like https://www.merlinmotorsport.co.uk/p/misab-anti-vibration-rubber-mounting-washers-csa005

where the stud is nutted to the engine.
Maybe the rubber sandwich will provide enough give.

Sorry but that will not help. Don't forget that, except in the rare case of there being a seperate thrust bearing, the boat is being pushed along by its engine mounts.

Www.solocoastalsailing.co.uk

 

[Lon nan Gruagach]

Sorry but that will not help. Don't forget that, except in the rare case of there being a seperate thrust bearing, the boat is being pushed along by its engine mounts.

Www.solocoastalsailing.co.uk

Well that thought opens a large can-o-worms...
If it is a linear displacement of the engine that is causing the stud to fail then it would be the shorter ones that die first. So, that implies that (lets use prop thrust) not only pushes the engine forwards, but because the longer stud is less rigid then the engine will also twist (yaw)... nasty, very nasty.
To prevent that then the simplest solution is to make all studs the same length. If the long one cant be shortened then its pair across the engine needs its mount dropped so it is the same length.

 

[chrishelen]

I have managed to shorten the offending stud by 12mm by packing the mount up. Hopefully it will work. I have a busy day today. fingers crossed.

 

[rogerthebodger]

I have managed to shorten the offending stud by 12mm by packing the mount up. Hopefully it will work. I have a busy day today. fingers crossed.

Could you fit a spacer between the top of the mount and the underside of the engine stud where it is clamped to the engine foot.

This would reduce the bending stresses on the stud.

 

[chrishelen]

Good idea. I had thought about welding an inch block on the underside of the engine mount bracket, with a hole in it of course. Wonder if it would work?