Originally Posted by JPA Cate
It WILL work for a while, but in the case of the OP, if there's rust in the top, there will also be rusting spots where he cannot see them. An epoxy patch (we used some Marine
Tex) to seal around a leaking fuel gauge on an aluminum
diesel tank) will work. But the rust will still spread: rust never sleeps. Rust converters are only temporary. Of course, rust only happens where iron is present, so was not a factor with our patch.
Dinged the gas tank on an old car once and patched it with Marine Tex. Was traveling without access to tools so did a quick and dirty repair IE crawled under the car as far as I could, reached in with a wire brush and hit it a few times, then reached in with a big glob of Marine Tex and smeared it around the spot.
Intended to do a better fix later but never got around to it and the repair was still good a few years later when I gave the car away.
BUT that was a car where a gas leak would be unlikely to cause an explosion and kill you. If the OPs boat
is gas powered I would pull the tank and do a proper repair. Diesel I would give it a go with Marine Tex. I love that stuff.