Fuel Tank Leak

[John Dickson]

Sunday I added 100 gallons of fuel to each side bringing tanks to 3/4s full and docked boat. Checked ER on Wednesday, all good. Thursday nite, I have 2 gallons of fuel in bilge. I have DD 671 TIs, the fuel supply is at the bottom of the tank, it is dry. The return goes in the top of the tank, it is dry. The boat sat for 4 days before any fuel showed up. The tank appears to be seeping approx 2 gallons per day.

I traced the fuel to the aft corner of the starboard fuel tank where I can see it seeping out from under the tank. There is probably 1/8 inch clearance beneath the tank and the stringer/shelf on which it sits due to the tank tabs holding it in place. The fuel appears to be seeping out from beneath the tank to the lowest aft corner and then running into the bilge. I have already transferred as much fuel as I can to the port tank.

The tank is aluminum and 23 years old. I am north of Detroit and looking for ideas as to where else to look or what may have caused the leak, a shop to pump the tank out and if anyone can recommend someone in the Harrison twp area that can assist me in the diagnosis. Can these tanks be repaired in the boat? Lined? Bladders? This tank is outboard of my starboard engine and cannot be removed.

Any suggestions would be appreciated.
tx john

 

[SKYCHENEY]

We had a guy in our marina with a Grand Banks that had a tank leak (iron tanks). He pulled alongside another boat and pumped the fuel off to his neighbor. Then they cut the old tank up and replaced it with several new aluminum tanks that they manifolded together. That was the only way to get them in there.

My suggestion is to find a friend that will take the fuel. Give it to him if you have to as it will be cheaper than calling someone to haul it off.

 

[yachtsmanbill]

Ahhh, the age old dilema about fuel tanks! Aluminum IMHO is prone to fatigue cracking. I would cut a large access hole in the top to make a cold repair from the inside... JB weld etc. the leak appeared after adding fuel no? You may get away with not having to empty the tank, but I would clean it while in there... ws

 

[John Dickson]

At this point it appears the leak is likely due to water corrorsion over the years inside the tank. I have owned the boat 3 years and that tank did have a small amount of water in it evidenced by racor cleaning the first year. Replaced deck fill gasket. No water in racor for past two years. Previous owner did not use boat much.

I would like to either repair tank or perhaps follow skys suggestion. However, after pumping tank, what is best course for cutting hole in it. I have a large side access (4 feet). What risks are there with diesel fumes and what tool would be best? Die grinder, torches? I am thinking that if I can get side access that I could clean out and have a new bottom put in.

Thoughts?

 

[Captned]

IMHO I wouldnt use a torch!

Captned
MBMM

 

[ron6785]

Boy I don't know how much luck you would have with cutting a access plate in the side of the tank. First the chances of it leaking over time would be probable I would think. Also the tank should have baffles or fins connected to the top of the tank so if you cut a hole in the side you'd only be able to clean effectively to the baffle in the first chamber. I had to cut one out and it's not alot of fun.

Obviously repairing the tank while in place is the preferable solution, which means finding the leak and then determining if you can cut an access cover close enough to effect a worable repair.

Did I understand you to say the tank only leaked after to filled it to 3/4 full?? Once the tank is empty and bilge is clear of fumes you can drill a hole in the tank and cut it with a jig saw, depending on the thickness of the aluminum. If you cut a square hole you can even use a skill saw.

 

[rrrestorer]

Why do you think its the bottom? It didn't leak untill you brought your fuel level higher. I would think your hole is near the top.

 

[Trojan]

Use a hole saw or a sawzall. There is very little chance of diesel fumes igniting. Providing you don't get any thing red hot. There would be no sparks cutting aluminum.

BILL

 

[Robby]

Ahhh, the age old dilema about fuel tanks! Aluminum IMHO is prone to fatigue cracking. I would cut a large access hole in the top to make a cold repair from the inside... JB weld etc. the leak appeared after adding fuel no? You may get away with not having to empty the tank, but I would clean it while in there... ws

There are epoxys abn adhisves mad specificly for fuel tank repairs.I've used them on old car tanks and they do work and hold up well.Check out your local auto parts store and Yes I love JB Weld.

 

[John Dickson]

Thanks for all the responses gentlemen:

Today, sunday, the leak stopped as quickly as it started, now I am really puzzled, I am going to pull the fill hose and inspect and replace. I had previously looked at it and it seemed ok, however after 24 years, it needs to be replaced anyway. I had transferred approx 50 gallons two days ago to the port tank and the starboard tank continued to weep. Just can't figure this one out. At least I can go home and get a good nights sleep tonight and then back out tomorrow to see if my luck holds.