Boat floor replacement

[JBBarry]

I have a 1994 18 foot Starcraft 1810ss - a typical fiberglass I/o bow rider. I am replacing the floor on the port side. Do I need to use marine grade plywood or is standard exterior grade good enough? Should the underside of the floor be coated and if so with what?

Thank you,
JBB

 

[chevymaher]

If the floor is bad chances are it is alot more than that you got to replace. Boats rot from the bottom up. Floor is the last thing to rot

 

[JBBarry]

Thank you for the prompt replay. The idiot who owned the boat before me had a problem with the port side seat. He did a makeshift job to refasten it to the floor and put a lag screw through the gas vent line. Over the past three years the foam under the floor became saturated with gas and then rotting the plywood from below. I have the demo done and now ready to put it all back together. The fore/aft stringers are fine. I need to replace a small section of stringer just adjacent t the leaking vent line. All else is sound.

 

[Woodonglass]

I agree with CM but to answer your question, Ext. Grade Normal plywood will last as long as you own the boat and longer. The key is the resin/glass coating. The underside of the deck should be coated with a coat of resin and then another coat of resin with CSM applied. Same for the top but I'd use a layer of CSM and then a layer of 6oz cloth.

 

[JBBarry]

Woodonglass - Thank you. What is CSM?

 

[Woodonglass]

Chopped Strand Mat. Check out US Composites online. Use their 635 Poly Resin Probably gunna need 2 gallons or resin and 3-4 yards of CSM and the 6oz cloth

 

[oldrem]

CSM is Chopped Strand Mat

 

[JBBarry]

Thank you, again. What weight CSM would you recommend? Also, I will need to refill with foam. Might you have a product recommendation?

 

[Woodonglass]

USComposites online will have ALL you need. 1.5oz csm and 6oz fabric. 2# foam is all you need. Calculate the cubic feet that you will need to fill and buy the right sized kit.

 

[JBBarry]

Thank you, all. One of the worst jobs I've ever done but my only alternative is to take it out and sink it.

 

[Woodonglass]

Yeah, boat restoration is a Hot, Stinky, Sweaty, Itchy job but...In the long run she'll be better than factory and you'll KNOW that it was done right and you can depend on it lasting a good long while.

 

[JBBarry]

Thank you for the encouragement. Three more questions, if you will. Should I run a bead of some type of adhesive like maybe 3m 5200 where the plywood rests on the stringers? The original installation was put down with 1 inch staples. Do you think stainless screws would be better? Lastly, referenced earlier is "2# foam is all you need". Are you referring to the 2 part expandable foam? Is there a brand or something more specific I should be looking for? Greatly appreciated, thank you. JBB

 

[Woodonglass]

I'd recommend using PB (Thickened Resin) on top of the stringers and plain old deck screws for the deck.
I'm talking about a 2 part foam that's sold by the weight of the finished product by cubic foot. 2# per cubic foot is whats most generally used. Check out USComposites online. They have all your supplies, at good prices and good explantions about all the products.

 

[JBBarry]

Thank you, sir. My project tomorrow is cutting and fitting the deck plywood and ordering all other supplies. Hopefully next weekend I will be installing and glassing the plywood and the weekend after filling with foam. I am in in Western NY so hopefully I will salvage half of the boating season. If you happen to have some expertise in steering problems I would appreciate any advice you might have with regard to most post in that section of this forums. Thank you, JBB.

 

[JBBarry]

Sorry about my typing skills. My wife can type a million words a minute. I cannot spell very many words a minute and find it difficult to hit less than 4 keys at a time.

 

[Woodonglass]

Hmm not sure what you mean by your steering problems