As I recall these are not sandwich or cored decks under the teak overlay. I believe most of these boats are plywood decks sheathed with one layer of mat and polyester resin top and bottom. The teak decks are laid dry atop the decks with a rabbet joint seam detail. These plank seams are payed with a thiokol compound similar to BoatLife. Decks are usually roughly 3/4” thick, counterbored 5/16-3/8” and fastened with you name it then bunged.
Leaks on this type of construction are virtually impossible to locate and address. Normally by the time water ingress is noticed the leakage and water migration has been going on for some time. The sub deck is almost always five ply Lauan plywood that has very little resistance to inter-laminate bond failure and fungal decay. The screws used in the deck planks are almost always driven dry so water migration is a common problem. When the interior or deckhead surface is glassed, as are most, it’s difficult to track and ID leaks. A rather simple and less destructive method of confirmation is to take a 1/2” core sample from the outboard areas in the lazarette and other suspect but accessible areas. You only want to core deep enough to check the plywood and not into the teak. A moisture meter properly used will do pretty much the same but nothing is as convincing as a core.
Good luck
