We are in the process of rebuilding a M-16 Scow from the 70's. Its a little race boat that scares the heck out of you on a windy day. i opened up a soft spot in the floot to reveal a few square feet of rotten balsa. Looks like the whole floor is wet but the majority is bonded to both skins and still strong.

What should i do? Its a race boat that i will probably outgrow in a few years. Its taken almost 30 years to get this bad. Can i just replace the rotten balsa and leave the wet untouched?
the deck is bad too so i cut a small hole(didnt want to mess up the nonskid) and cleaned out the core with a coathanger chucked in a drill.

I'm hoping i can pour a 2 part foam with low expansion properties into the deck. has this been done?
its open and i plan on leting it sit for a few weeks to air dry. Work will start by march to be done by june. Any advice or suggestions are appreciated. I am not looking to rebuild for the next 30 years rather the next 5.
I need a source of balsa around philly.
I posted an introduction in the boats section.
regards