Leaking fuel tank

[The Dread Pirate Robert]

Just returned from a great three week cruise to find we have a small leak in the port side fuel tank of our Jefferson Sundeck. I have located the drip and it is on the bottom and inside side seam in the back of the tank at the weld joint. I have viewed it with an endoscope and the drip is about every second. The area has some rust but that is not clear in the picture yet.
Has anyone tried to repair such a leak with JB weld and then perhaps fiberglass over?
What is the process of removing and replacing with new tanks? I have already heard about removing the engine then replace the tanks or cut a hole in the side of the boat to remove and replace then repair the hull.
Are there other options?

 

[MYTraveler]

Are there other options?

I thought I had a leak in a prior boat and explored this extensively. They were steel tanks, and I never got as far as figuring out where the leak was coming from before discovering that it was a fuel line that was leaking. Anyway, my conclusions were: 1) the idea of putting a bladder inside the tank was not feasible due to the baffles. And cutting the baffles would leave inaccessible sharp edges that would end up cutting the bladder. That is still my favorite solution, though I never figured out exactly how the baffles would be cut and the bladder protected against the sharp edges. It might be worth exploring.

The only other option was to remove and replace the tank, which would require either removing the engines (not then in need of an overhaul), or cutting a whole in the side of the boat. I saw an episode of Deadliest Catch in which one of the boat was getting new engines. They cut a big whole in the side, but that was a steel boat so easy to repair structurally good as new and appearance didn't count. With fiberglass, that is a major undertaking and I questioned whether access to the inside of the hull, after the fuel tank was replaced, would be adequate for proper fiberglass work. I was assured that it would, but I remain skeptical of that.
Removing the engines was a lot of work and the engines were reasonably accessible. Even so, it wasn't much more expensive than cutting the boat (and maybe less). At the end of the day, that is what I would have done, absent a good bladder approach.

 

[Pete Meisinger]

I have repaired leaks in gasoline tanks with a purpose made putty-like stuff. Worked very well. Not sure if it will work on diesel but it is worth a try. The reason most repairs are not attempted is because it is rare to be able to find the leak.

What do you have to lose?

A replacement would start at $10,000, probably twice that.

pete

 

[Marco Flamingo]

I'm just going to copy this from a prior post of mine:

>I just went through this, although I didn't bother to find out exactly where my tank was leaking, other than to make sure that it wasn't leaking at a fitting that could be repaired. The look of William's tank is the same as mine and probably the same construction. Fiberglass over steel. Apparently the idea was that the layer of fiberglass would keep the exterior from rusting and the diesel would keep the insides from rusting. Seems to work for about 40 years.

My tanks are so close to the hull that I could barely get my fingers underneath. But were I could, I could tell that the thin layer of fiberglass had delaminated. If I pushed up, the layer would oilcan and leak out somewhere, although the tank itself was sufficiently stiff that it didn't flex. This would squirt out the diesel in the fiberglass "blister." It might then take a day or two to fill the blister back up with diesel from the pinhole leak in the tank. No leaking for two days and then leaking again. Grrrr. It would also have been possible to pressure test the tank and have any bubbles or leakage hidden under the veneer of fiberglass.

I didn't have inspection ports in mine and felt that this was a project for a professional, or at least somebody with experience. If I had already had three 8" inspection ports, one in each tank section, I might have tried coating it myself. The only remaining difficulty in a DIY job is cleaning out the tank. I hired a guy who had a steam cleaner, a wet shop vacuum, and a helper. He ran them all at once and cleaned out the tank in about 30 minutes. Best part of that was he hauled the goop (and there will be goop) off to the hazmat site. That was included and took some of the sting out of the $2,800 price tag.

Since the entire bottom and up the sides 6" was coated, I don't know and don't care where the hole was. That reminds me of the scariest part. Before he put in the coating he whanged on the bottom of the tank with a steel marlinspike. He said that there was no point to coating a tank that he could punch through. My tank passed the test.

Now the question is do I bite the bullet and have the other tank done?

Good luck.<
______________

 

[FlyWright]

Here's a link to the threads I posted documenting the discovery of fuel contamination and the subsequent repair of my leaking fuel tank. The thread documents the products and methods used along with the trail of discovery 4 years later that led to the leak and failed tank.

https://www.trawlerforum.com/forums/s32/diesel-fuel-tank-sealant-36019.html

https://www.trawlerforum.com/forums/s32/diesel-fuel-tank-sealant-36019.html

 

[Trentmcb]

While I'm new to the boating world I have repaired mild a steel diesel fuel tank with JB Weld on an Excursion. I ran on the truck on Veg oil with a small added tank for diesel that was part of a kit sent from the factory veggie oil conversion company. It arrived with a pinhole leak in the bottom. Of course, I didn't discover the leak until I had filled it with fuel. I emptied the tank as best I could wo removing it, cleaned the corner, and put on fast set JB Weld. Still holding 10 yrs and 250k miles later.

 

[jungpeter]

While I'm new to the boating world I have repaired mild a steel diesel fuel tank with JB Weld on an Excursion. I ran on the truck on Veg oil with a small added tank for diesel that was part of a kit sent from the factory veggie oil conversion company. It arrived with a pinhole leak in the bottom. Of course, I didn't discover the leak until I had filled it with fuel. I emptied the tank as best I could wo removing it, cleaned the corner, and put on fast set JB Weld. Still holding 10 yrs and 250k miles later.

Hi Trentmcb. Yes, it's possible to repair leaking marine diesel fuel tanks. Solutions such as applications of various forms of "mouse milk" to the interior of tanks, weird suggestions of welding repairs from INSIDE of a tank (huh? Assuming you could wiggle into the tank, who in their right mind welds in an explosive atmosphere, in a confined space, inside of a highly flammable boat hull?), to JB Weld on the exterior.

Bear in mind that if your Excursion fuel tank DOES fail again, it will do so onto the ground under your car. Other than a mess, it's unlikely the USCG and/or the EPA will smack you with a $800K fine. Not so much if a marine diesel fuel tank fails.

After 70+ years afloat, on vessels ranging from nuclear submarines through large powerboats, to inflatable tenders, it has been my unfortunate experience that marine fuel tank failures result in REPLACEMENT vice repair. Given tankage is never treated as a replacement item by pleasure boat manufacturers, planning (and budgeting) for their inevitable failure is a sad fact of life for the vast majority of us poor schmucks in this lifestyle. Sigh.

Regards,

Pete

 

[jungpeter]

I have repaired leaks in gasoline tanks with a purpose made putty-like stuff. Worked very well. Not sure if it will work on diesel but it is worth a try. The reason most repairs are not attempted is because it is rare to be able to find the leak.

What do you have to lose?

A replacement would start at $10,000, probably twice that.

pete

Hi Pete

What's to lose? Well, maybe only $800K or so, should your "putty-like stuff" fail and you dump diesel oil into the water within sight of the EPA and/or the USCG. And the reason most repairs are not attempted is NOT because it's rare to find the leak. It's because repair is virtually IMPOSSIBLE, even if it's staring you in the face. Sure, there's anecdotal evidence of success with "mouse milk" or "putty-like stuff". There's HUGHLY uncountable anecdotal evidence to the contrary.

But your boat, your money, your choice.

Regards,

Pete

 

[HopCar]

Could you cut up the tank to remove it and replace it with two or more smaller tanks that could be fitted without destroying the boat?