Bilge Water
Water could be leaking in from around the gunwale moldings. That's where my leaks were coming in. After or during a rain, check the fabric inside the cabin for dampness. Unless you know for a fact that it's sea water, it could be coming in from any kind of deck hardware. It could even be coming in from the lower gudgeon on the transom, if it is sea water. Last spring, I cut an 8" hole in the center of my inside transom for a Beckson deck plate. I was able to replace my self bailing hose, remove both of my gudgeons, re-caulk, and install it back, all by my lonesome. Don't ever try going head first into the lazerett to reach it. Get an 8" hole saw and mount a deck plate, but watch out for the stern light wire when you make the cut. Good luck Captain Jack!Joe