How high can an engine be on the mount studs?

[bbalan]

Hi All,
During a long rebuild on the hard, the hull of my 1969 Cross 46 trimaran shifted a bit, slightly changing the angle of the prop shaft as it goes through the cutlass bearings in the stern tube and strut.

The engine (Yanmar 4JH2TE) needed to be moved up a bit so I could align it. I'm at the very top of the mount studs on the front of the engine so will weld a 1/2" shim under those mounts. The aft mount has just under 3/8" thread showing beneath the lower nut (see pic).

Should I put a 1/8" shim under the aft mounts or is that overkill?
I'm also changing all 4 mounts during this process (giving the R&D mounts a try).
Many thanks for any advice.
Cheers,
Bruce
s/v Migration
Phuket, Thailand

[Zach]

How long has she been back in the water?

If I were in your shoes, I would keep the prop shaft loose and bolts out, let her float for a week or two and see if floating gives her old shape back.

Boats are funny like that, particularly wooden ones!

[bbalan]

Hi Zach,
I put her in the water without the shaft connected and let her sit for a week before connecting the shaft the engine. Now she's been in for 2 months. I'll check the alignment again before doing the mounts but I don't think it has changed much.
Thanks,
Bruce

[JK n Smitty]

From the photo it doesn't look too bad. I had a my mounts much higher than that. I had a 1/2" shim made of SS at a machine shop. So a 1/8" shim I probably wouldn't worry about. My boat had lasted 13 years at the top of the studs.