I keep meaning to pull that aft panel down before getting underway in order to get a better look while motoring, but somehow as soon as I get out of the marina, the sails go up, the motor goes off, and before I know it, I'm sailing and can't remember there ever being any other problems.
Here's an interesting article:
The Hull-to-Deck Joint - Good Old Boat It looks like this is one of the few places where 5200 is entirely appropriate. I'm not sure what was applied originally, but there seems to have been a pattern of poor workmanship in sealing that joint, particularly at the transom where it regularly goes under water. I guess it might depend on how well the joint can be cleaned out and opened up in order to accept new sealant. If (when?) I ever have to perform this surgery, I might consider applying a couple layers of fiberglass over the joint and then following that up with 4200 to seal the screws that attach the rub rail as Jay described earlier in the thread. Then again, I have zero (0, zilch, nada) experience with this so who knows?