JO JO,
All good advice above. I did a floor in my 18' starcraft, and it wasn't too bad. All gas and such was in the back and all electrical was run high (under the gunwales). I went with something like carpet (ordered from cabella's) and 3/4" treated plywood. Original floor was 1/2", created a small problem when some holes didn't line back up in the dash boards. When talking to the guy at cabella's he mentioned that he had recently done his floor. My boat is Aluminum and his was glass, my boat has styrofoam and his had that blown in foam (expanding type stuff you'd use to insulate the home). My foam doesn't retain water but his did, he said it lightened his boat by nearly 1,000lbs!
If you have a garage and can suspend some things from the ceiling, it makes the job much easier as you don't have to disconnect everything. Chances are (as in my case) your "soft spots" are allready completely rotted and your actually walking on the foam underneath. If you plan to keep the boat, I reccomend you do the whole floor, plus seats (in the bow area). Don't let anybody try to sell you marine grade plywood, it is the best but the price will knock you out! My original floor wasn't treated at all and still lasted over twenty years!
Good luck, let us know how it turns out. - Slime
