Rockdoc, check with Jamestown Distributors for boatbuilding and finishing supplies. They are the Grainger of boats, and will probably steer you toward the West System epoxy if you want to do things right. Their catalog (free) is a great source of info and they have discussion groups and tech tips on their website. Since you are going to cover the plywood with carpet (I think), another less expensive alternative to West System epoxy would be Liquid Wood from Abatron. Thin it and flood the plywood surface, brush off any excess before it cures, then do it again. If you can get it onto the edges of the plywood, that's even better. This stuff will wick into any gaps or joints and waterproof them, but it will also wick into places where you might not want it, so use some masking tape and proceed carefully. I use a lot of the Abatron products on old house restoration projects, and the Liquid Wood is like magic for the right applications.
