Originally Posted by
rustybucket
First of all, I can clearly see coring in the part, looks like it's either plywood or foam, hard to tell exactly from the pic. Also, I've done some work on my tuna door top as well and it had 1/2" plywood coring. So, you do have coring, it looks to be in ok shape, but impossible to tell for sure from the pic. If you have any rot, NOW is the time to fix it before you epoxy it back together.
The original adhesive would absolutely NOT have been epoxy. BUT... the original adhesive would have been applied at or near layup allowing it to bond with the polyester resin. The best solution for bonding polyester resin long after the fact is epoxy. I would not look to what was originally used for a guide as to what to use today. The original adhesive will NOT be the adhesive you want to use.