Wet Fuel Tank Compartment

[Clockwork]

I have an 88 sailfish 25 that I recently acquired. I pulled the floors over the tanks and found a thick gooey slime covering every surface under there. I spent an hour shop vac-ing it out and left the floors off for weeks to let it dry. It did dry, so I put the floors back in temporarily while im working on a fuel tank replacement, now its wet in there again and the boat is covered.

The rest of the bilge is dry. Any ideas on what causes this. Condensation? How do I prevent this? The bottom of the floors are even dripping.

 

[VeroWing]

Most likely condensation, or could be water in stern bilge traveling back up piping to fuel cell compartment. I/O powered Gradys built then had plugs installed in engine bilge area to isolate fuel cell compartment, keeping water out of fuel cell compartment, and fuel out of engine compartment in case of a fuel cell leak.

You may want to consider coating your new fuel cell with a coating that will decrease "sweating" of tank.

 

[Pez Vela]

Any ideas on what causes this. Condensation? How do I prevent this?

Most likely, and my boat ('87 Sailfish 255) exhibits the same characteristic. I pop open the deck plates on the fuel tank hatch covers and leave them open unless the boat is in use. This allows the compartments to "breathe." The boat cover keeps debris and rain water from entering through the deck plates when they're open.

 

[richie rich]

That compartment gets wet for several reasons......the pie hole covers on top are very prone to leaking....the screws that hold the deck/hatch cover also leak, and the joint around it and the rest of the deck can leak....condensation is a big yes as well.....when the boat is covered and stored for winter, I leave the pie holes uncovered.....and if I'm doing some PM's in the spring like changing fuel lines or something, I'll just remove the entire hatch cover for the winter months to let it dry out. Moisture also comes throgh from inside....the center PVC drain sticks out past the main bulkhead under the helm...trapped water can slowly leak back into the compartment where the inner stringer passes through the bulkhead as the glass they used doesn't always wrap tightly around the stringer....I'll put money on the inner stringers that are holding up the tank are waterlogged and rotted....you will see when you pull the tank. And lastly, the compartment only has a pass thru limber hole on one side the center drain.....that means if there is water on the opposite side of the center drain, it will stay there forever and only as the level gets higher than the center drain, will it flow over the top to the other side and drain back towards the stern.....its not the best drain design on that particular hull....