I've already started the process of taking off all of the tru hull fittings both above and below the water line, I'll certainly be checking the exhaust tube area closely, my boat looks like it may also have had problems around the anchor well drain so that's another area I plan to investigate thoroughly.
Thanks for the tip about the stud finder, I'll give that a try. The moisture meter apparently pegs at a low level, which hopefully means the problem isn't beyond hope.
