Flexi coupling broken? (Video)

[Mark Payne]

Hi just doing winter maintenance and checking and I have found this.
Something is not right!

Took a little video here: https://youtu.be/sURBFnqNQno

The engine is a Yanmar JH4E. The coupling is a Vetus Uniflex going onto a 35mm shaft.

I looked again and I am now sure that the shaft is not in the centre of rotation of the coupling. I don't think the shaft is bent. I think there is a transverse error between the rotation centre of the engine and the shaft side of the coupling.

Is this a thing anyone has seen? Is this an adjustment within the coupling?
I don't think it has anything to do with engine alignement (?).

Is the coupling duff?

Cheers

Mark

[Mark Payne]

Actually, having looked at it again, there is no way the aluminium cast outer housing should be not tight to the flange all the way around.

Something is coming adrift here....

[Privilege]

If you can view the coupling with the engine running and in gear, and it is misaligned you will see the shaft vibrating from side-to-side. It will also probably vibrate noticeably.

Another way to tell for sure is to remove the bolts from the coupling so that the coupling will sit at its natural alignment. Someone with more expertise than me can advise but the tolerance for alignment is within thousands of an inch. It should be an easy fix as you then just adjust the height of the feet by adjusting the bolt on them until the faces are properly aligned.

[Mark Payne]

Just an update:

I removed the coupling and it is indeed falling apart! Its an easy fix to be honest. The hex socket head bolts (4) that hold the engine side stud flange to the rest of the coupling are lose. Once the stud flange is bolted to the gearbox output flange these bolt heads are hidden/covered but they can clearly still rotate and loosen themselves off.

Taken the unit home for better inspection and a rebuild with thread lock!

Mark

[Suijin]

I was going to say, the oscillation looks (although hard to see from the angle of the video) like it goes right up to the coupling, putting the problem pretty likely right at the coupling itself.