Here are some images from inside the bilge area. The floor is now partially removed and the rest will come out in the next few days. The part of the floor I have removed has rotten balsa core and is completely saturated. There are lots of sources for the water that get dammed up behind the vermiculite including the sink and its plumbing, various overhead leaks like the port lights, winches etc. all contributing to the pool of water that gets trapped. I suspect that even with the vermiculite all gone there would still be water sitting in this low area, so my plan is to do a couple of things when I rebuild this deck. 1) Provide access so that the water that builds up between the sink and the cooler can be wiped up. 2) build the deck such that there is some air movement to help dry the area.
Removing this floor is fairly difficult even with all the right tools. I first tried to figure out if there was a way to salvage it, but then decided if that was even possible it would be even harder to do. I have cut the bottom of the tub just even with the floor with an oscillating multi tool and what seemed to work best was a carbide abrasive blade normally used for grout. When I used this tool with anything that had teeth, they just got devoured and burned up. Then it was on to the skill saw cutting chunks that could be pried up. The vermiculite has just enough bond to make removing large sections fairly difficult.