Floor Replacement

I have a 78 Ski Nautique and I am going to have to replac a section of the floor on the left side around the back left corner of the engine bay. Does anyone have any tips of how I should do it. What type of wood should I use, would pressure treated plywood work or should I use marine plywood? How many layers of fiberglass? On the top of the wood or the bottom or both? Any tips will be gratly appreciated.

Jeremy,
Have you dug into the floor yet to see what's going on underneath? IE: stringer condition/wet foam? A close inspection is needed as it may not be just the floor.

No on the treated ply because the chemicals and the fiberglass resins don't like each other. and the marine grade ply isn't needed. Exterior is the same glue system and is fine especially when it's primed/sealed first with CPES. (clear penetrating epoxy sealer)

Do some searching and reading here and I feel you'll find some interesting threads on floors/stringers. Good info!

BTW, we'd still love to see some pictures posted of the boat. What did you ever do about the hull/paint/gel???