Re: Musty boat smell under floor
The bilge was pretty grotty when we bought our boat and everything was covered with a mix of diesel residue, oil and slime.
I drug in a hose and flushed the bilge with fresh water. Shop vac-ed it dry, then hit everything with Tilex. Let it sit for a few minutes then with the pump turned off filled the bilge with fresh water, flipped the pump on and pumped it out again. I did this a couple of times and it made a huge difference in the smell. That was in '08 and the bilge pump is still going strong.
The biggest difference in boat odors was going to a dripless shaft seal. No seawater in the bilge now, just condensation from the AC. This winter I'll add a shower sump and plumb the AC drain into it; and the bilge should pretty much stay dry.
You might also try some canberra gel on board to kill odors. The stuff's not cheap but it works wonders.
95 Catalina 30 Island Time
“If a man is to be obsessed by something, I suppose a boat is as good as anything, perhaps a bit better than most" - E.B. White