Re: can i launch withwet underfloor foam?
I think you have some choices to make regarding safety, my main concern would be the strength of the transom. Any rot/flex in this area could be disasterous.
Soaked floatation foam won't keep the boat afloat if the boat is flipped or swamped, on a small river this wouldn't be much of an issue...on the ocean it could be life or death in an emergency.
While looking for my current boat I looked at hundreds of boats, most had wet foam to some degree although if you asked the owner they would deny it. I soon realized some amount of moisture is to be expected in a boat stored outside, the only way your ever going to keep it perfectly dry is stored inside and kept out of the water.
I would guess that the transom wood on 90% of the boats out there have water intrusion to some degree, marine plywood does not degrade unless it starts to rot. I drilled 6 holes in my transom to test the wood condition before I mounted my current motor, the bottom 2 inches had water in it but the wood was still strong and not rotten...am I worried? Nope, I sealed them up with 5200 and every year I re-drill the bottom holes to drain out the water so it drys out over winter and does not freeze and thaw causing damage to the transom.
Boats get wet, carpet gets wet, wood gets wet...if these items couldn't take it then they shouldn't be in a boat. I stopped being scared of water intrusion in a wood reinforced boat since I seen all of them have it to some degree, the AL boats I looked at were the worst it seems...I guess people think AL boats can get wet and fill with water and not cause damage WRONG!
So you got wet foam, so does everyone else...dry it out. Is the transom rotten to the point it is dangerous? This is the question you need to answer for yourself. Boats float by displacement, as long as it still does that it will float. If the foam is wet and soaking its not going to float if the boat is filled with water, if it is a river runner I would rather it sank while I swam to shore...insurance can buy me a new one.
The real drawback of wet foam is the weight, its like carrying around two extra people in the boat.
The last issue you didn't address is the fiberglass condition, water can infiltrate fiberglass if it is aged and cracked from UV exposure, a tapping hammer test will tell you if there are any voids in the hull...this is how they test fiber helicopter blades.
If the transom is strong and sound and the fiberglass is not degraded I think you have a good project there that needs some TLC to make it right, I would certainly take it out for a river test without reservations as long as the bilge worked properly and I remembered to put the drain plug in. Take it easy and go slow, rebuild the boat as you have time at the end of the season...take note of all the other old boats on the water that look like yours and rest assured their foam and wood is in similar condition...they are just in denial.
