I'm about to pull out my transom, I'm working on a aluminum 16' Sylvan deep V. The back of the transom is covered by aluminum, the inside is exposed but mostly under the cover that diverts the water out the drain hole.

I found it very difficult when looking for marine plywood and the suggestion of to use or not to use were overwhelming. Since the only wood that is exposed is under the pan that diverts the (near the fuel containers) and all of the wood that I have pulled out of this thing so far was outdoor plywood marked "underlayment", would it be OK to use a double layer of outdoor plywood coated in resin for this?

Regardless of what wood that I use, assuming that the transom has to be two layers of plywood sandwiched together, should I run the direction of the sheets opposite? Should I Gorilla Glue or Liquid nail the halves together?

 

Have a look at this from Boatbuilders.net: Rebuilding a transom.

I agree with his use of epoxy and marine grade plywood. I used CDX once (to build a new doghouse) and it separated after a few years, even though I sealed it with epoxy.

 

Use marine plywood it has different glues made for this purpose that outdoor plywood doesn't use, and use marine epoxy to seal it up. This is a job you only want to do once so you will want to use the best materials possible.

 

I was ordering my Epoxy from a boat builder yesterday, he tells me to use ACX instead of marine plywood???? He claims that Marine plywood has some sort of an oily preservative that will keep the epoxy from soaking in.... Just when I thought I had everything figured out, now I'm confused..

 

What was the transom made of? Use that. (Probably marine ply sealed with epoxy, right?)

 

Not sure, it is pretty much rotted beyond recognition..LOL. The original piece was painted with some gray paint and appears to be fairly knot free. It's really heavy which could mean marine plywood or just the fact that it's so waterlogged.

I do have one section that is fairly solid. Its 2 plys of 3/4", can I tell what material by counting the plys? I just purchased some non-marine outdoor 3/4" yesterday for something else, if I count the plys in that and compare, would marine have more?