Re my successful repairs of seriously delaminated decks: you MUST remove just about all of the crumbled old brown foam from the underside of the top skin, and from the old foam surface too. If there little left of the stiff white polyurethane foam, replace the foam with new.
If the inner fiberglass cloth skin has fallen off too, the whole thing has to be replaced. Ick! This is what happens after years of sitting uncovered on the beach, full of water!
If so, can one 1. Bend the foam, 2. Epoxy cloth to the concave underside and get it to stick, 3. Glue it into the hole in the deck, 4. then put a new top skin on? Answer- Yeah, but it will (probably) look like a Goat's butt. Big job too.
