Fuel tank gave up

Pack Mule · Jun 6, 2019

This is a 150 gallon fuel tank that is original to the boat. The tank sprang a leak this weekend. It had about 80 gallons in it that I was able to transfer to my other 4 aluminum tanks . The aluminum tanks were installed in 2002. Without this tank I will still have 275 gallon fuel capacity in the 4 aluminum tanks. This tank is on port side in engine room. It’s approximately 2-1/2 ft square x 6-1/2 ft long.
We need more water capacity. My plan is to cut it out this winter and install a new water tank. I can get to this through the engine room door. I’m hoping to get another 50 gallons at least of water. This “should” be easier than my last water tank install.

RT Firefly · Jun 6, 2019

Greetings,
Mr. PM. Bummer. The first thing that springs to mind is trim. As you use up your water on the port side and/or your fuel on your starboard, will you be able to keep William somewhat level?

Pack Mule · Jun 6, 2019

Hey RT ,
William seems to already have a funky “built in” list to starboard. There are two 62 gallon fuel tanks directly across on starboard side from this tank. I have 75 gallon each port and starboard under aft deck. It will be a challenge but maybe not as a great a challenge of only having 20 gallons of water capacity.
I know that being organic is really cool these days, but Joy says I’m a little too organic for her lately.

RT Firefly · Jun 6, 2019

STB · Jun 6, 2019

Hey Pack Mule,

Where is the leak?

If the whole tank is rotting out from water at the bottom -- that's rough.

If there is an isolated bad spot in a weld or similar, you can probably clean it/drill it out and fix it with a fuel tank epoxy. In my last boat there was a tiny bad spot in a weld around a fuel tank fitting. I was able to clean the corrosion around the fitting with a dremmel brush tool; drill through the point leak to get clean, good metal inside all the way in; and pack the cleaned out defect and a bead around the fitting with fuel system epoxy. It worked like a charm and lasted at least years and, to my knowledge, and counting. I tried to dry out the repair area as best as possible, but there was likely still oil residue -- and it still bonded fine. The epoxy was from an auto parts store, was specifically for fuel tanks, and claimed it would work even with oil residue.

When I was crawled in the working on it, I actually noticed that it was the 2nd repair -- the other one had seemingly been done decades earlier. The fittings were originally tapped and threaded and had subsequently been welded. One still looked good -- the other was the one with the corrosion leak problem.

Aquabelle · Jun 8, 2019

gkesden said:
Hey Pack Mule,

Where is the leak?

If the whole tank is rotting out from water at the bottom -- that's rough.

If there is an isolated bad spot in a weld or similar, you can probably clean it/drill it out and fix it with a fuel tank epoxy. In my last boat there was a tiny bad spot in a weld around a fuel tank fitting. I was able to clean the corrosion around the fitting with a dremmel brush tool; drill through the point leak to get clean, good metal inside all the way in; and pack the cleaned out defect and a bead around the fitting with fuel system epoxy. It worked like a charm and lasted at least years and, to my knowledge, and counting. I tried to dry out the repair area as best as possible, but there was likely still oil residue -- and it still bonded fine. The epoxy was from an auto parts store, was specifically for fuel tanks, and claimed it would work even with oil residue.

When I was crawled in the working on it, I actually noticed that it was the 2nd repair -- the other one had seemingly been done decades earlier. The fittings were originally tapped and threaded and had subsequently been welded. One still looked good -- the other was the one with the corrosion leak problem.

Is 17 years an acceptable life for an aluminium tank? Properly installed, I wouldn't have thought so. Do you know the cause of the failure ? How thick is the aluminium ?

STB · Jun 8, 2019

For the curious, the epoxy I used was JB Weld SteelStick.

And, as I am thinking more about it and remembering better, I didn't get all of it dry first.

It was initially a slow ooze-becomes-drop-and-drips leak from a pinhole. I cleaned the outside of it and around the fitting and then drilled through it with a 1/16" or 3/32" bit. When I did, it became a real leak.

I pushed a few tiny balls of epoxy into that, leaving a good ball on the outside, then dried off the rest of the area I cleaned and wiped it with acetone, then I did the final pack over the hole and around the fitting, making a relatively flat ring about 3/16" thick, deeper right against the fitting and shallower at the very edges. The rung was probably 1/4" wide. I did it all very quickly, before and of theb epoxy started to set.

Fuel tank gave up

Pack Mule

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