Experience with Por 15 tank sealant for aluminum fuel tank holding diesel?

[mforum]

I’m pretty sure I have a pin hole aluminum fuel tank leak and am debating using POR15 tank sealant.

Any thoughts on using this product or other solutions aside from “that’ll be about a thousand” for a new tank?

It seems there are varied outcomes out there from worked well for years to total failure. I’ve used the degreaser and metal prep but am having second thoughts before applying the final tank sealant product. I’m thinking to just try to apply POR 15 over a 4 to 6 inch area where I think the leak is coming from rather than the entire inside of the tank as the instructions describe to prevent large spread blistering or flaking of the sealant over the areas that are oxidized inside the thank I can’t get to because of the baffle.

Tank is 19-20 gallons on an ‘86 catalina 27. I’m pretty sure it’s coming from the deepest most forward center corner where the sediment tends to accumulate.

Thanks,

 

[Project_Mayhem]

Maybe filling the tank with a dye and welding would be a more permanent solution?

 

[dlochner]

Once the pitting and leaking starts, it will continue. The only real solutions are selling the boat and making it someone else's problem or replacing the tank. At 36 years, the tank is reaching its life expectancy.

 

[mforum]

Maybe filling the tank with a dye and welding would be a more permanent solution?

In January of 2023 I suspected it was the tank, so I pulled it. Pressurized it, checked for any exterior foam bubbles with soapy water and nothing. Then I filled it with water with a UV fluorescent dye and let it sit for several nights checking for any leaks under black light which I couldn’t find. I put the tank back thinking possibly it had leaked a little with healing through the sender gasket under a very full tank. For then next 1 and a half years or so I kept the tank level at about 1/2 to 3/4 full and no leaks. In August, I filled the tank again to near full and 2 weeks later there was about 1-2 oz of diesel in the bilge.
I’m not sure how a welder would tackle the problem as it is an old tank.

 

[Rich Stidger]

I'm with @dlochner - Replace the tank, lose the band-aids.

 

[FastOlson]

Note also that diesel seepage is common on old gaskets under gauge senders or clean-out plates on the tank top, too. And when the tank is really full, an aged fuel hose that seeps around the connection point or along the hose will be a problem. While you're there....... DO replace the old fill, vent, and engine hoses also. After about 20+ years any and all will start to get dodgy.

 

[Rich 35.5]

Do you really want to depend on paint to stop a leak that could cost you many thousands in fines? Replace the tank, and sleep better at night...

 

[capta]

Unfortunately, over the last 6 decades of boating, I've had more than my share of holy tanks. Obviously, unholy is preferable, so I've found a pretty effective way to do this. I always carry a quick setting, two part, underwater epoxy. I've found that it will also dry quickly when in contact with fuel, but it really isn't very effective unless you have access to both sides of the hole.
Rummage around in your screw stash and find a screw just a bit larger than the hole, with as deep a thread as you can find. Mix the epoxy (I have always used 2 part JB Weld) to harden quickly and goop it around the threads and the hole. Thread the screw into the hole and, as neatly as you can, goop it around the screw head. The screw will hold the epoxy in place as it cures both the epoxy inside the tank, as well as outside.
It's a permanent cure so we might as well make it look good, right?

 

[seanshine]

Thanks capta. I used this same procedure a couple of years ago. I has worked perfectly. Nuff said. I didn't want to reply because there are a lot of haters on this board

 

[thinwater]

Lining diesel tanks is accepted practice by standards. However, the usual procedure involves a very good cleaning and sand blasting. I've been involved in many lining projects, and I've inspected many lined tanks decades later. As the OP describes his situation, I don't see how you get a good bond. The linings are not typically forever, perhaps 20 years, which is good.

The key will be the cleaning. When you think it is good enough, do more. And do not paint at all beyond the very clean area--that will start the peal.

 

[mforum]

Lining diesel tanks is accepted practice by standards. However, the usual procedure involves a very good cleaning and sand blasting. I've been involved in many lining projects, and I've inspected many lined tanks decades later. As the OP describes his situation, I don't see how you get a good bond. The linings are not typically forever, perhaps 20 years, which is good.

The key will be the cleaning. When you think it is good enough, do more. And do not paint at all beyond the very clean area--that will start the peal.

I decided not to use POR15 for the entire tank as there is a baffle in the center and I can’t get to the aft half of it well enough to clean it. I have a few emails and calls out out to local fabricators for a new tank build. It probably doesn’t make sense to line the new tank as that probably would be longer than the life of the boat and me. I’m thinking my next step is to fill the tank with UV fluorescent dye put it under pressure and let it sit for a couple days to see if I can confirm the leak is at deepest forward port side corner weld point as there was a very slight water film on the outside tank when I was degreasing and washing it out. I the pressure test and fluorecent dye way back in January of 2023 but couldn’t confirm any leaks and didn’t have any till August of this year. According to Don Casey, my sealant options are polysulfide, polyurethane, or silicon (not a good option with Diesel). It sounds like polyurethane is more resistant to Diesel than polysulfides but also more permanent. How does this compare with epoxy like the JB weld that capta mentions as above?

 

[mforum]

Unfortunately, over the last 6 decades of boating, I've had more than my share of holy tanks. Obviously, unholy is preferable, so I've found a pretty effective way to do this. I always carry a quick setting, two part, underwater epoxy. I've found that it will also dry quickly when in contact with fuel, but it really isn't very effective unless you have access to both sides of the hole.
Rummage around in your screw stash and find a screw just a bit larger than the hole, with as deep a thread as you can find. Mix the epoxy (I have always used 2 part JB Weld) to harden quickly and goop it around the threads and the hole. Thread the screw into the hole and, as neatly as you can, goop it around the screw head. The screw will hold the epoxy in place as it cures both the epoxy inside the tank, as well as outside.
It's a permanent cure so we might as well make it look good, right?

I was able to confirm the suspect leak with dye under black light (green dot inside the red drawn circle). It’s coming from the welded joint at the deepest forward port bottom corner.

Putting a screw here doesn’t seem like it would work well as it would just create more fractures in the joint corner. What about using a polysulfide or polyurethane sealant or just epoxy on inside and out? I also planning to talk to a welder to see if it’s possible to just fabricate a new forward side, remove the old one and re-weld the new one with a new joint.

 

[FastOlson]

I also planning to talk to a welder to see if it’s possible to just fabricate a new forward side, remove the old one and re-weld the new one with a new joint.

I once brought this very idea up with a local tank welder. He said repairs are possible, but very tricky. He said that it's tough to grind the old metal clean enough for a good bond. Often he was able to make such a repair OK, but sometimes it would fail in some small place, later. I got the message that the tank would have to be cut back far enough to be completely away from any pitted or compromised metal.
The advice was generally to replace a 30 or 40+ year old tank with a new one. After decades, the old tank does not owe you anything, in any case.

You did not ask, but when I needed a better tank, I sourced a beautifully-fabricated new tank from https://coastlinemarinetanks.com/
I was able to have a new one built with a baffle, two large clean-out ports, and a new sender for an electric gauge. Every fitting was right where I wanted, the the metal was thicker than the original one, also. Since the OEM tank left some unused space where it was installed I was able, working from my own new mockup, to have the new one built with considerable more capacity as well.

You have "choices and options," as the old saying goes......

 

[mforum]

I once brought this very idea up with a local tank welder. He said repairs are possible, but very tricky. He said that it's tough to grind the old metal clean enough for a good bond. Often he was able to make such a repair OK, but sometimes it would fail in some small place, later. I got the message that the tank would have to be cut back far enough to be completely away from any pitted or compromised metal.
The advice was generally to replace a 30 or 40+ year old tank with a new one. After decades, the old tank does not owe you anything, in any case.

You did not ask, but when I needed a better tank, I sourced a beautifully-fabricated new tank from https://coastlinemarinetanks.com/
I was able to have a new one built with a baffle, two large clean-out ports, and a new sender for an electric gauge. Every fitting was right where I wanted, the the metal was thicker than the original one, also. Since the OEM tank left some unused space where it was installed I was able, working from my own new mockup, to have the new one built with considerable more capacity as well.

You have "choices and options," as the old saying goes......

Coastline isn’t too far away. I sent them a message. thanks!

 

[capta]

I was able to confirm the suspect leak with dye under black light (green dot inside the red drawn circle). It’s coming from the welded joint at the deepest forward port bottom corner.

Putting a screw here doesn’t seem like it would work well as it would just create more fractures in the joint corner. What about using a polysulfide or polyurethane sealant or just epoxy on inside and out? I also planning to talk to a welder to see if it’s possible to just fabricate a new forward side, remove the old one and re-weld the new one with a new joint.

If you can get the tank out, then it's a simple, and reasonably inexpensive job, to have a regular machine or welding shop to fix your leak. Most of my leaky tanks have been on a delivery or a vessel that must be back in service the next day.

 

[jibes138]

If I was repairing an aluminum tank I’d want to make sure it was anodized after welding to protect the aluminum from oxidizing rapidly in the moist environment.
might want to consider a plastic tank from Moeller. I found one that had all the fittings in the right places and very cost effective versus metal.

 

[thinwater]

I was able to confirm the suspect leak with dye under black light (green dot inside the red drawn circle). It’s coming from the welded joint at the deepest forward port bottom corner.

Putting a screw here doesn’t seem like it would work well as it would just create more fractures in the joint corner. What about using a polysulfide or polyurethane sealant or just epoxy on inside and out? I also planning to talk to a welder to see if it’s possible to just fabricate a new forward side, remove the old one and re-weld the new one with a new joint.

NO. Many years as a chemical engineer in the petrol business. None of those will work for this. The suggestions are for sealing sending units, for example, not this.

Epoxy rated for this service, inside and out. Super clean, well-sanded surface extending beyond the repair.

 

[mforum]

Thanks all for the input. I was able to find a local welder who built me new tank.