Help with Under-Floor foam

[wolverine1]

Does anyone know if the under-floor foam filler in a 1975 Sea Ray SRV 190 is structural or for flotation...
I bought a 1975 Sea Ray SRV 190 from my wife's cousin as a project. The hull and engine are in good shape but the floor is bad. I cut it out and have disposed of most of the filler. (It was pretty wet!) I would like to replacce the floor and stringers without having to replace the filler but I'm not sure if the hull would be sound. I need help!
I appreciate any input! I am fairly handy with tools but I have never rebuilt a boat.

[woodboat]

My dad's Chrysler bow rider used the foam to support the cheap stringers that were made from plywood. All the foam was soaked and the plywood stringers rotten. I made a new stinger and floor support system out of 2X4s and glassed the whole thing to the existing floor. I then redecked it with 3/4 plywood and again laid on the polyester resin. The boat has never been so strong or so light. It of course is no longer unsinkable but it probably has not been so for many years before.

[PAR]

Those era boats had foam of the open cell variety, which absorbs moisture like a mop, as you've discovered. It may have served to stabilize the stringers, but was likely to satisfy floatation requirements. You can purchase polyurethane foam, a two part mix, which produces non-absorbent closed cellular structure floatation when cured. Most fiber glass supply stores will have it available.