Re: Fuel Tank Leak

James Alton


   My tank had what looked like a gooey brownish tar like deposit in the lower part of the tank.  The upper parts of the tank looked pretty clean.  I found that Acetone would cut the deposits so I added some Acetone  (a liter or so) and rocked the tank back and forth.  I then removed the shut off valve and drained as much of the solvent out as possible.  Then working through the shutoff valve hole I swished around a pc. of cloth on the end of a flexible wire to help remove the deposits and soak up the remaining Acetone.  I probably repeated this process at least 10 times at which point the drainage was coming out clean and the inside of the tank that I could see looked shiny so I this method seemed to work pretty well.  I was able to dry out almost all of the Acetone using dry rags poked into the shutoff hole.  Acetone wants to evaporate quite quickly so I just left the fill, vent and shut off valve hole open for a couple of days until the Acetone smell was essentially gone based on the smell test.  I then placed a wet dry vac on the ground well away from the boat and using a long hose drew fresh air through the tank for an hour or so to be really sure that all fumes were removed before the welding.  Recognize that a wet dry vac is an ignition source so if you use this method be sure that essentially all of the fumes are gone and that you place the vacuum well away from anything important just in case!  I was confident that the Acetone was gone at that point but if something bad was going to happen I wanted it to happen away from the boat and not during the welding.

    All of the cracks were located on the forward end of the tank and the tank fits up pretty close to the bulkhead.  I used a dental mirror initially to find the cracks.  In retrospect and given that removal of the tank is really not that hard to do, I think that I could have saved time just moving the tank into the pass thru area so that I could fully inspect the tank directly.  I was actually able to inspect every surface of the tank, even the bottom.  The crack that was seeping was not very obvious,  quite fine.  I will try to attach a photo to this post.  The other cracks that I found were even less obvious.

    The welder was naturally concerned about possible fumes in the tank.  I explained the process I used to clean the tank and then he smelled the fuel fill pipe and was happy with the lack of  fumes.   I spent a few hours going over the whole tank ahead of the welding process, cleaning and polishing areas to locate all of the cracks.  I marked everything that I was able to find.  The welding only took about 2 hours and the tech welded  a lot of spots that we not leaking.  

Best of luck and if you have additional questions that I can help with let me know.

SV Sueno
Maramu #220


-----Original Message-----
From: Dennis Johns <sbmesasailor@...>
To: Group Moderators <>
Sent: Tue, Dec 29, 2020 12:54 pm
Subject: Re: [AmelYachtOwners] Fuel Tank Leak

Hi James,

Thanks for your response, sorry that you had to resolve this problem before me but glad I have an alternative to cutting through the deck.  Yes, I know the tank fits in the companionway to the aft berth, I've had it out before....Some questions:

1)  Did you do the cleaning yourself or if not what type of person did you hire?
2)  How did you find the crack(s)?  Were they obvious or is there a special method? 
3)  Wasn't the welder concerned about residual fumes?
3)  How long did the process take?



On Mon, Dec 28, 2020 at 11:01 PM James Alton via <> wrote:

   According to the measurements I took of my seeping fuel tank and from the posts of others that have removed the Maramu fuel tank it is apparently possible to remove the fuel tank with minimal interior removal.  In my case, I found some cracks in the metal/welds on the forward end of the tank,  one of which was seeping.  The only areas where I had cracks were at or close to the welds, the rest of the tank looked excellent.   I drained, flushed and cleaned the tank with solvents.  Vented to remove the solvent fumes.  Then detached the tank and moved it into the center of the pass thru to the aft cabin, letting it sit on a couple wooden blocks an added some lines to keep the tank upright.  The tank is awkward but really not that heavy, maybe 150 pounds?  I was able to move it around in the area of the pass thru by myself with a little ingenuity.  In my case,  moving the tank to the middle of the pass thru  fully exposed the cracks in my tank and they were welded which has so far cured the seeping that I had.  Before reinstalling the tank,  I replaced all of the carpet that the tank was resting on and removed the foam that had absorbed fuel.  I inspected the interior of the tank where possible by the way and found no corrosion inside at all.

Best of luck,

SV Sueno
Maramu #220


-----Original Message-----
From: sbmesasailor via <>
To: <>
Sent: Mon, Dec 28, 2020 9:38 pm
Subject: [AmelYachtOwners] Fuel Tank Leak

Hello Amelians,

My 1982/3 Maramu appears to have sprung a leak in the fuel tank.  This happened once before but it was just the inspection port plate that needed tightening. 

The Maramu appears to have had the deck applied after the tank was installed.  Has anyone had their fuel tank removed for repair?

What are my options?

Thanks in advance.

Dennis Johns
Maramu #121 

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