fuel tank starboard side .

1981 island gypsy leaking tank it is on the upper end of the tank any body got any idea s other than pulling the whole boat apart .

Is your tank full?

You might try sealing the leak with JB Weld.

Some years ago I ended up with a 1976 Yamaha DT 250 motorcycle. The tank had been left with old fuel , and condensation had corroded a few pin holes. Classic bike with a 70's (orange/white) paint scheme, so finding a replacement would have been a challenge.

I found a product online made specifically to re-coat the inside of the tank - 10 years and it's still fine. But obviously that was a small tank that I could remove. Still, if you do a Search online you'll see several products that first seal the leak(s) with epoxy then coat the inside. The tank would have to be emptied to do that and you'd need access to the inside. So an outside epoxy job (i.e: JB Weld per hmason) would be a lot easier if the leak's above the fuel level, and not widespread.

One of two things is probably true: (a) your 36 year-old tank corroded in a small area due to a saltwater drip of some kind, such as the prop shaft slinging a tiny bit of water at it, or maybe a deck leak, or (b) it's corroded all over from inside and this is the first sign of a wider problem...potentially on both sides of the boat.
(I realize that's not encouraging - sorry.)

I don't know IG's but best case is smearing sealer on it, and usually worst case is cutting it out and replacing with several smaller tandem tanks. A more permanent - albeit more expensive - fix. But fuel = blood. You don't want to lose much.

It occurs to me that intentionally pumping out a tank full of fuel takes forever, while traveling by boat makes the fuel disappear way too fast!

Actually, for people maybe fuel equals water, and oil equals blood.

I am dealing with a similar situation currently. If you're looking inside the tank it look impossible to clean enough to seal so Monday I took a Sawzall and remove existing tank. Plan to place with a fiberglass tank partially built in place

my boat is currently on the hard. It had a fuel tank leak,i considered the epoxy option but that meant cutting additional inspection holes for viewing and cleaning ( baffels in tank prevented access to the tank ends). Long term cure for me is putting in poly tanks. According to the yard cost would be comparable NOT CHEAP!!!.

motion30 said:

I am dealing with a similar situation currently. If you're looking inside the tank it look impossible to clean enough to seal so Monday I took a Sawzall and remove existing tank. Plan to place with a fiberglass tank partially built in place

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Bummer. I feel your pain. Are loosing tank capacity? How are you going to build the tanks? Any info would be great.

i ordered the tanks thru Moller they make fuel tank i will end up loosing 100 gal currently haveor had 150 gal each side. I am going down to two 51 gal tanks. Ocean Marine in Portsmouth is doing the work. give me a call if you have other questions Gene

Larry M said:

Bummer. I feel your pain. Are loosing tank capacity? How are you going to build the tanks? Any info would be great.

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I plan to built the new tank the same size over a male mold
Then I plan to cut it in three pieces , and then glass each piece together in the boat. As i go I will have to cut a large access panel in the back of the tank to Glass the final piece. What no big deal to Glass that back in place.
Hardest part is it is out the board of the motor in the twin-engine boat and I do not fold and bend as easy as I used to

Mary L, a leak "on the upper end" of the tank is a little unclear, do you mean on the top of the tank? Maybe the filler tube attachment to the tank? Pics or more information would help.
A leak at the top is better than a leak at the bottom.