How to clean "Varnish" out of old gastanks

[396_WAYS_TO_SPIT]

We are trying to clean the "Varnish"(old gas-about 4 years old) out of my buddy's fiberglass tanks. What do you guys think will work. What do you guys think about pool acid? Will it bother the fiberglass?Any info would be appreciated. Thanks 396

[DansBlown73Nordic]

I think I would try a couple gallons of carb. cleaner. Its about the only thing I know of that will break the varnish down. I don't think it will touch the fiberglass. I would try it in one side and see what happens.

[Stab-n-Steer]

396,
There is a company, POR15, that has gas tank restoration products. I used one for a car gas tank a few years ago and it worked great. For a fiberglass tank they recommend a cleaner called "Marine Clean" to remove the gum and varnish... here's the link: http://www.por15.com/metalprep_degrease.html#MarineClean
Good luck,
S&S

[Schiada76]

I used a couple of pints of parts dip in the AL tanks on my old flat just poured it in and poured it out and they were perfectly clean. Worked great, don't know if it can hurt fiberglass though.