This is info for whatever it is worth, to add to the body of knowlege on this subject, as I understand the subject. With that intro I don't need a disclaimer.

I have a drain at the bottom of the keel of Solsken, #82. Every season I pull the plug and water pours out. I can't figure where it comes from. The bilge, up to the floorboards has been meticulously covered with several coats of Gluvit, so it should be waterproof. The keel bottom has been sealed before being painted with anti-fouling paint.

When I rehabed it, I had the boat lying on its side while I carefully repaired the bottom of the keel, and Gluvited it.

Although there is always a modicum of water in the bilge, below the pumping level, it appears to stay at that level - although that might be presumptious. Perhaps it is filling as fast as it is going out.

Gluvit is supposed to be flexible, and unlike fiberglass, not dependent upon whether if bonds everywhere to the surface of the bilge. So I should not be concerned about a crack. I can not believe the plug leaks (in which case, where does the air go.

Good luck finding the monster.