1st Boat

My brother and I have just bought our 1st boat and it's in need of some repairs. The floor is a little spongey, so replacement is next on the list. I haven't ripped it up yet, but have a few questions before I do.

1 - I know PT plywood is used for the floor, but how do you waterproof the underside of the wood?? fiberglass it??
2 - the stringers most likely need replacement too, so how do you attach them to a fiberglass hull??
3 - I hear alot of core foam talk so I assume my boat will have this is the hull. How do you replace this if it's soaked??

Boat info: 19?? DeltaCraft 175 XLT ( 17.5 ft bowrider )

 

These are all questions that have cropped up before. Plywood can and should be sealed with epoxy before installation. No glassing is necessary with plywood unless the surface is subject to abrasion. Hence. it can make sense to glass/epoxy the top surface.
Stringers attach in the same manner they were originally attached---- they are glassed in. The difference is, you will likely improve over the original method by using epoxy rather than polyester in bedding them and glassing them. After all, the polyester did fail. After sanding prep, bedding is the first step, where you create a thickened epoxy mush to press the new stringers into. Squeeze-out is scraped clean, fillets added (can be done with excess goo), after which several layers of cloth and/or mat are layered--- more details if interested.
Your boat may or may not have any foam coring. Probably not, but if soaked, it must, of course, be replaced. Chances are you have flotation foam which may be semi-saturated. Good time to address it. Foam-cored hulls were a rarity a few decades ago.

Alan