Re: Comments welcome
You might try coring the foam to see if it's dry in the middle. Take a 3/4" or larger boring bit and drill down in the deepest part to see if you can find moisture. I haven't tried this, but it seems like it might work.
One of the methods I've seen for drying a boat's foam (and I'm not suggesting you do this, just sharing) is to drill through the outside of the hull into the foam at about two hundred spots, just pepper it with holes, and let the moisture drain out and the air get into the foam, then fill the holes with spray in foam and then reglass the outside of the hull.
I'd just go with good marine grade plywood (meranti 1088) and make sure you saturate it with epoxy resins and then do a good glass job like tashasdaddy said. That should do it.
While you have the floor up, can you read those markings on the plywood the manufacturer used? Can you see what grade ply they used? Do you know if that's orginal to the boat? Just curious because looking at a lot of these boats being redone, it seems that the mfg.s are all using different stuff. Sometimes it seems like it's whatever is handy.
