First post ever been lurking for a long about a year.  I'm a newbie to boats.  Me and a friend bought a 76 Sanger Super Jet a little less than a year ago.  Took the seat out to find a big rotten hole in the floor.  I was going to just patch the hole in the floor but after closer inspection found that the floor had been replaced before and was not done very well either.  I ended up removing the entire floor to find more damage from foam under it that held water like a sponge.  The floor that I removed was not even in the location of the original.  It was just set on top and glassed in really crappy.  Heres some pics of my progress. 
I plan on coating the bottom of the floor with a coat of resin before glassing it in.