I’m about ready to install my transom core, it’s gonna be made of three layers of 1/2” marine plywood, with woven roving between each layer. The first two plywood layers are already bonded and are going to be installed as soon as my Core-Bond B70 shows up. The third piece will be installed once the first two layers are in. The remaining build will be using VinylEster resin.

My question is wether I should use Epoxy on the end-grain, just around the edge of the transom pieces to help waterproof the edges. Hopefully no water will ever get there, but I’m thinking “just in case”. I could use painters tape to keep the epoxy from running onto the face of the plywood, as I know that you can’t use Vinyl or Poly over Epoxy. Again, I’m just wondering about around just the very edge of the transom.

Am I over-thinking this? Or should I just glue it in with the core-bond and never mind the edge?

Over thinking it.....but the edged will technically be sealed once you glass everything over the final time.....so unless you are planning on cutting any holes into the edge sections later i wouldn't worry too much about it....but if you want piece of mind just use the same Vinyl ester you are using now....it will work just fine. You can even put some heat lamps on the edges to warm up the wood so the grains expand a little and let the resin soak up a little more. If you want to get crazy you can bond all your layers together...once its cured you can then coat the edges and then bag it all and place it under a vacuum to suck the resin into any open cavities etc....still would need to sand the face for final bonding purposes afterwards though....

Thanks Wally,
I think for my own peace of mind, I’ll seal up the edges like you recommend with some vinylester…
After seeing what water did to my last transom, I will do anything I possibly can (within reason, lol) to avoid having to do it again!!!
Cheers!!