Cleaning 1" varnish from 75gal Aluminum Fuel Tank?

[rdh2059]

I see a lot has been discussed about cleaning fuel tanks out, but little in the way of cleaning large installed tanks. My boat is a 26' Tollycraft and both tanks have over an inch of varnish sludge on the bottom. How do I clean those out? <br /><br />Remove the tanks and replace?<br /><br />Dump 20 gallons of lacquer thinner in each and let it soak, then drain it?<br /><br />What is the real solution to this dilemma? I really would rather not have to pull both tanks. They are 75 gallon aluminum tanks and will require pulling of both motors to do right...<br /><br />Thanks for any help you can give,<br />Rick

 

[SS MAYFLOAT]

Re: Cleaning 1" varnish from 75gal Aluminum Fuel Tank?

Hi Rick, When I first got my 27'er, It had lots of garbage in the tank. It was a 100 gallon one.<br /><br />I had to remove the tank from the boat. I cut 3 access holes in the top of the tank. The holes were about 8 x 10 inches. That allowed enough room to get in there and scrap up the excess trash. Then I used degreaser and scrubbed the inside until it was nice and clean.<br /><br />Now to cover the holes, I used 1/4" plate aluminum. I made them 12 x 10". I centered them over my cut outs and drilled holes about one inch apart around the patch. I then took the thick piece and threaded them with a tap. Redrilled the holes in the tank a bit bigger to allow my screws to drop through them. I made a cork gasket, covered it with #2 permatex. Placed the patch inside the hole and fastened it up. I'll post a few pics since I just recently took my tank out. I'll do that later on this evening. The pic will help make you understand my jiberish that I just spoke of.

 

[Chris1956]

Re: Cleaning 1" varnish from 75gal Aluminum Fuel Tank?

Rick, What is the condition and expected remaining life of those tanks? If it is a lot of work to pull them once, and they will be worn out in 2 years.....

 

[SS MAYFLOAT]

Re: Cleaning 1" varnish from 75gal Aluminum Fuel Tank?

Here is the pics of my tank. I filled it up with water completely. Marked where my clean out holes will be. Used a hole saw for the corners and a jigsaw to do the straight lines. Just make sure you don't cut into a center support. To hold the aluminum plate up into place until getting the screws in, I used duct tape to make a tab. Just be sure to fill the tank with water or otherwise you could go kabluey! It's been about 5 years since I did that job and it hasn't leaked or shows any signs of stress. The thickness of my tank skin is 1/8".<br /><br />

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<br /><br />EDIT: I forgot to mention, I used #10 fine thread stainless screws. I got small Orings to fit over the threads of the screws. The Orings must be suitable for gasoline. I run the screws up through the plate first squeezing the oring againt the plate. I made a cork gasket, coated both sides with permatex #2. Put the plate inside the tank and pull the plate up so the threads of the screws go through the holes in the tank. Put permatex on the threads, flat washer, and a selflocking stainless nut. <br /><br />This was the only way that I could see saving this tank do to the trash that was inside. I filled 3 2lb coffee cans full of crap. The gas was so old it was like syrup. Nasty smelling stuff. I don't know if this would work for your tank or not. Good Luck.........SS

 

[rdh2059]

Re: Cleaning 1" varnish from 75gal Aluminum Fuel Tank?

The tanks were well installed, well wired and are quite thick. I think they are between 3/16" and 1/4" thick. The insulator between the tank and all contact parts still appears to be intact with no friction wear points that I can tell. The tanks do hold pressure, so there is no fractures or leaks in them now. <br /><br />They're just a royal pain to remove. I guess the only way is to remove both engines, disconnect the tanks, slide them down to the stern, turn sideways and pull through the engine access door. If I do have to pull them, it is also sounding like the best way to resolve this is to cut off the top of the tank clean them completely then if they are worth reinstalling, then treating the aluminum and sealing the outside.<br /><br />This project as most projects do, seems to be getting larger... <br /><br />Rick

 

[SS MAYFLOAT]

Re: Cleaning 1" varnish from 75gal Aluminum Fuel Tank?

I know what ya mean Rick. I was hoping I wouldn't have to pull my tank again. This project was just to do the transom. Then it was to install water tanks using 4" PVC tubing, then it was some major rot in my outter stringers. So to do them, the tank had to come out. I know it is a major job and didn't want to do it again. Just getting all the useable gas out was fun in itself. Just not sure how you could do it while it is in the boat though. Again Good luck and keep a posting!

 

[thunderroad]

Re: Cleaning 1" varnish from 75gal Aluminum Fuel Tank?

Back when everything had a carburetor you could buy a 5 gallon bucket of cleaner that you would submerge a carb and related parts in overnight and it would do an amazing job of disolving varnish. It was pretty intense stuff. Definitely required rubber gloves for handling. I haven't seen the stuff in years but that might be because all of the machines I encounter in my work are diesels. <br />We used to get it from NAPA. Might be worth a try. Sounds like a BIG project to remove the tanks.

 

[robpoe]

Re: Cleaning 1" varnish from 75gal Aluminum Fuel Tank?

You can still buy carb dip here in Kansas. It has Hexavalent Chromium in it (the stuff that Erin Brockovich sued PG&E over), and if you accidently get some on your hands, you'll taste it in a couple of seconds (because it soaks through your skin, into your bloodstream and to your tongue!).

 

[PHILRAJOTTE]

Re: Cleaning 1" varnish from 75gal Aluminum Fuel Tank?

Re: Cleaning 1" varnish from 75gal Aluminum Fuel Tank?

hey rick
how old are your tanks if they are15 years old i would recommend replacing them with new ones the coast gaurd does not like patching them it also voids any insurance claims