leak in my water tank....

[CaptSmith]

So..I opened up the cabin sole , cut the top off the tank, and found retro fitted baffels of uncoated 1/4 aluminum plate, footed on 2x4 wood blocks, covered with coal tar epoxy, and goobs of black silicone......the blocks (6 total)where fastened to the tank sides by 2 (only!) each 3inchx#12 SMScrews (I think my leak)...the tank is coated with coal tar epoxy...no perforation or obvious anything other than the stupid 2x4s fastened to the tank walls with sheet metal screws, the baffles footed onto the 2x4's...QUESTION is....what kind of sealant to bond the 3x3 angle (replacing 2x4) to the coal tar coated walls...leaks started last summer, just drip/drip....my "evil plan" is to remove the wood blocks, fair out the coal tar where the blocks where, re-coat that area only, then fasten the epoxy coated angles and baffles back with machine thread thru fasteners and big flat washers, bedding the coated angles onto the walls of the tank, and then after caulk cure fill it, check for leaks..
the boat, 42 Irwin CC ketch...the tank is not OE...and is in good shape, I believe installed with-out baffles, baffles installed by second owner...
200 gal, long wide and shallow

[GordMay]

Greetings and welcome aboard the CF, CaptSmith.

[tkeithlu]

You're not going to want to disconnect this after it's done, so I'd suggest bedding the machine screws that go through the walls of the tank with 3M 5200 as you insert them.

By the way, you can save a partial tube of this rather pricey stuff by wrapping it up and freezing it. I've got one tube that i've been using for little jobs for over a year.