Varnish Removal Method

[reefrunner42]

I have seen this topic discussed with many different methods suggested. I just wanted to share what worked for me. I purchased a boat that had sat with about 35 gallons of fuel in an 80 gallon aluminum tank for 6 years. I have used the boat the past 2 summers without issue as long as I kept the Volvo Penta AQ225 below 3000 RPMs. As soon as I went above that, the boat would run for another 5 minutes and then start to stutter and then die. Sometimes it would not start back up. I found that if I connected a 2 ft piece of hose to the fuel pickup tube and blew down into the tank, it was normally so backed up that I couldn't push any air into the tank. I hooked a dive tank to it and opened the valve slowly. That would free the pickup tube and the boat would start. I finally removed the tank from the boat last weekend to discover what seemed like handfuls of loose material in the bottom of the tank. I used a pressure washer through the sending unit hole to try to break up more varnish that was on the walls. After getting as much out as i could, I poured 1 gallon of acetone in the tank along with 7 allen wrenches about 3 inched long each. I sloshed the wrenches back and forth multiple times on all sides and emptied the tank. I did this 2 times and then rinse the tank with water. Now the inside of my tank is varnish free!
I don't have a lot of experience fixing boats and have already learned a lot from others posts. I'm hoping that someone out there will benefit from reading the way I cleaned my fuel tank.
Now onto the task of putting the tank back in the boat and fiberglassing in the panel that I cut out to remove the tank...

 

[Bob_VT]

Re: Varnish Removal Method

I normally recommend that people use a big handful of nuts and bolts since they all can be fished out with a magnet.

Check it carefully for leaks. If you have a way to lightly pressure test it I would recommend it before you re-install.

 

[reefrunner42]

Re: Varnish Removal Method

Thanks, Bob. I did read that method to be suggested more often. My concern was that being smaller they would get stuck behind the baffle in the bottom. I did make sure though that 7 wrenches went in and 7 came back out! How much pressure should I use for a light pressure test?

 

[Bob_VT]

Re: Varnish Removal Method

5-10 PSI and have a spray bottle with soapy water on hand..... spray down the tank and watch for bubbles. If it hols for 5 minutes you are fine.....do not go too high on PSI start at 5

 

[Woodonglass]

Re: Varnish Removal Method

I don't like to use flammable liquids to clean the tank. I use my Turkey fryer (3 gallon Pot) and boil water and mix in some TSP (Tri Sodium Phospate) a great degreaser, a hefty squirt of DAWN dishwashing soap, throw in 2 dozen (yep I count em too) 1/2" nuts throw it in the back of my truck and go for a ride in the country on bumpy roads. When I get home, I usually have a very clean tank. I dump it all out, Blow it out with my air hose, Pressure test like BVT suggests and all is well in the Gas Tank World!!!