Refastening or relocating H-25 outboard-motor mount
Lpenrose, I am doing the same thing. The caveat I would offer you is about compression vs tension. Most people think they have to support the motor mount from falling off the boat. They beef up the mounting bolts and provide huge washers and backing plates, etc. In fact the only time you worry about that is when engaging reverse gear. The real issue is in beefing up the transom itself to take the compression of 9.9 HP pushing on it against water that's 8 times as dense as air.
It is vital that you spread the load of the two mounting rails over a bigger surface than they actually cover. I worked on a guy's 25.5 and his mount is (in the infinite wisdom of the post-Cherubini Hunter '80s) simply bolted to the transom... that 's it. Needless to say there are spider cracks all through the gelcoat in that area. The transom is slowly caving in from the press of the motor's thrust.
What I recommended to him (and am doing to my 1st-gen H-25) is a pair of G-10 plates, cut about 3/8" wider all the way round, bonded to the hull (use 5200 or epoxy) and then the motor mount bolted through those. This is a little better than the rails placing the whole load on the transom alone. I would have made them bigger but the transom is curved and G-10 doesn't like to be bent (in fact it just doesn't bend). So I elected to make vertical plates. The 5200 will actually provide a bit of 'give' further sparing the transom surface from a pointed load.
As for the backing plate inside the transom, with most of the thrust issue solved I just pierced the old plywood in places and pumped it full of epoxy like I've done to nearly every other old bit of wood on this boat. It is rejuvenated enough to not need replacing-- and again, as I said, the real issue is on the other side of the load, not here, so I don't really care about the plywood inside the boat any more than this.
I have solved the boarding-ladder issue for Diana by designing a very narrow folding ladder that mounts on my narrow IOR-era transom beside the on-center motor mount. The steps are about 9-10" wide. Why do you need anything wider in an emergency? It will fold up against the stern rail like a regular one. As soon as I have plans approved by my SS guy I can offer them to people.
On the subject of boarding ladders remember to have at least 2 or 3 FULL step spaces that extend BELOW the waterline, for unless you are an Olympic gymnast who can lift his foot to his chest whilst floating neck-deep in the water you will never get back aboard otherwise.
