Jsherm,
As long as the bottom is not leaking. The water actually cradles the boat better than anything else. No extra stress here or there. If you are not out for a sail or sitting in the rain, the bilge should be dry. It should be dry anyhow, but almost all older boats like this leak somewhere above the waterline. If the bilge is not dry, look for leaks around thru-hull fittings, keel bolts or CB pin, then cracks in the hull's exterior. You don't want her in the water after you find something like that. Rot and mold actually pull water out of the air and hold it so finding a rotted board that is wet doesn't automatically indicate a leak. However, if you think there is the possibility that such a leak might exist, don't put it in the water at all until you've either found or and fixed it or you've dried everything out thoroughly and are putting her back in the water as a test to help find the leak.
There are some things you can do to fix the rotted plywood in or out of the water. You will have to be the one to decide where it works best for you.
To arrest the dry-rot until you have time and facilities to do a better job, dowse the infected area with strong bleach and let sit over night. Then dry it out completely. Use heat and air exchange (a fan).
To fix it, remove all the infected wood you can and replace with either new wood and epoxy resin or just fiber glass. If you think there ous some need to structural support, mold ribs and/or stringers into it or add an extra 1/4" of marine grade plywood and encapsulate in glass.
There is no way for me to say if the wood is important to the structure ood the hull. It looks like it is intended to help.
I assume you've already had her out for a test sail when buying the boat.
- Will (Dragonfly)
