BLUEMOMENT

I'm reading your description to mean that the pin would limit the movement in extreme circumstances, a massive lurch or inversion.

The mount with the pin at the wrong place can't be carrying enough weight to compress the rubber to the same extent as the other 3.

Ash

Thinking about this further.

Nick and I are describing lining up a plain uncoupled shaft with either the central boss of the gearbox flange or the hole in the coupling bolted to the gearbox.

In your case, if the shaft is already connected to the box, and hence supported, then you need to check that your alterations leave the shaft central to the stern tube.

Ash

I had realised that. I'm wondering if I should slacken off the coupling all the way and do the adjustments somewhere near before I tighten it up again.

First job is to see if I can make this mount look like the other 3.

That is, first job after I dismantle the boat again to get at the engine

aquaplane wrote:I had realised that. I'm wondering if I should slacken off the coupling all the way and do the adjustments somewhere near before I tighten it up again.

If it is relatively easy to pop out the bolts, then it might be a good idea. You then know that the coupling isn't loading / unloading the mounts.

Give the engine a good shake between adjustments to ensure that it's sitting down on it's mounts.

Ash

Nick's advice to start with the propshaft centred in the stern tube is good. I used half an old cutless bearing on mine. There is just one wee problem though - it requires removal of the stern gland which may be the thing stopping the sea coming in. So much easier with the boat on the hard.

If it is an R&D coupling, they recommend .010" or better N,S,E & W.