... and how strong is it and how many problems have you had with it?
I'm sure that with a 9'-6" x 4'-6" transom, three plies of 3/4" (2-1/4") would give you much better lap and joint options on fabricating the oversized transom and would be many times strong than two 3/4" plies with a 3/4" collar around the outdrive. Build that 2-1/4" out of CCA plywood and encapsulate it in marine grade epoxy resin and you'd never have to worry about it again.
That is totally what I thought as well. Then the one that's in it has rotten! I couldn't believe it but it is, marine grade plywood, painted heavy with epoxy resin, rotten in about 10 years. I was shocked, now there must be a leak or some water ingressing that's assumed but I cant find it, im sure its there though.
So Im going to weld plates (fancy way of saying thick pieces) and drill and tap for all the attachments like stabilizers, sounder, fishhawk, swim platform, kicker motor bracket to eliminate the through the hull penitrations even though it will not rot doing it the way im going to.
I use the boat allot and its out in bad weather allot, and its going to get wet allot, that is not going to change
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Anyway because of that, Im done with wood even though I think its great 95% of the time.. I have worked on many boats with an alum stern just never one designed this way. I dont think its going to be hard and like different thoughts on it
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Just an intelligent discussion even if you disagree.