Engine replacement

[owen]

I am planning on changing my engine with a reconditioned one(3gm30 from 3hm)
The footprints are not quite the same with about 8cm difference with the longitudinal and 3cm on width.
My question is would it be best to drop the engine in , line up the prop shaft first and then mark the mounts position or work out the mounts first.
Thanks in advance

 

[sailorman]

You have the shaft position & angle, from that, work out the offset for the mounts allowing for adjustment the mount bolts, that how i did mine. It then involved cutting down the existing grp bed tops & reforming, including ss inserts to take the mounting feet fixings

 

[alahol2]

I found it easiest to make a very simple 'mock up' of the engine feet and shaft position. This can then be lined up in the engine bay and the bearers adjusted before starting with the actual engine.

 

[DanTribe]

I found it easiest to make a very simple 'mock up' of the engine feet and shaft position. This can then be lined up in the engine bay and the bearers adjusted before starting with the actual engine.

Good advice. I did an accurate full size drawing on A3 paper and made a template from ply and roofing battens. use this to check and mark feet positions and shaft centre. Adjustments are much easier to do in timber than in steel in-situ.
One small thing I learned. I photocopied my drawing. My photocopier was not 100% accurate, only millimeters out but it took ages to realise!

 

[Contest1]

You have the shaft position & angle, from that, work out the offset for the mounts allowing for adjustment the mount bolts, that how i did mine. It then involved cutting down the existing grp bed tops & reforming, including ss inserts to take the mounting feet fixings

Sounds like a plan!

 

[Tranona]

The differences are so minor and assuming the current bearers are wide enough and long enough best to bolt the engine to the shaft, line it up properly then drill for the new holes. If the old bolts were coach screws, plug the holes and redrill new holes. Worth checking the drawings for the height of the mounts to the centreline of the gearbox coupling as you may have to put packing pieces under the mounts or reduce the height of the bearers locally so that the engine feet sit roughly half way up the studs on the mounts. The critical datum point is your existing prop shaft coupling which is why important to bolt to that first and then locate the mounts to suit.

That is exactly how I did it changing from a Yanmar 1GM to a Nanni 14 with similar differences in mount positions. Had to put a 10mm spacer on top of the bearers to get the mounts at the right height, but otherwise it was very straightforward.