Any Advice On Cleaning Out Old Classic Boat Gas Tanks?

Old Gas TankFellow Woody Boater Bill Anderson asked this burning…non burning question.

I have been collecting boats for a long time. We get a few in every year. I now find myself with a few boats with very very old gas or dried up tanks. Any tricks to cleaning the tanks?? Let new gas sit in them or some other solution to break down the sludge etc??

Let her rip!

19 replies
  1. Troy in ANE
    Troy in ANE says:

    That is one thing this Ethanol gas is good for, cleaning out crud. With American Beauty I first “Polished” the tanks (the stuff that came out the first time literally looked like molasses), we then put in some Ethanol and transported the boat around and “Polished” a second time. I can still feel crud in the bottom of the tanks so I am now using a product known as PRI-G which is supposed to emulsify the stuff.
    Outboard cans should be a lot easier.

    • Bill andersen
      Bill andersen says:

      How did the pri-g work? My tanks are all in older inboard boats. Going to be a pain to pull some. Thanks.

  2. Brian K
    Brian K says:

    If you have a local radiator shop they can usually “boil” them out. I have used a local metal cleaning company as well. Gas breaks down pretty quick these days. Good luck

  3. Eric Zelman
    Eric Zelman says:

    Try the “Gold Standard” kit, motor cycle size. The complete kit will include cleaner, acid etch and sealer. You supply the nut and bolts for the shake out with the cleaner. I can send you a video link or more pictures. OMC paint and decals are also available.

    • Steve Haines
      Steve Haines says:


      Great restoration all around on the Wagemaker, my Daughter and I are working through a similar restoration of a 1959 IdealCraft. I am interested the process you used to remold the Wagemaker emblems as I am thinking we will be doing the same. I am also interested in casting custom rubber step pads for the boat in a similar fashion. Any info you can share would be helpful.


  4. m-fine
    m-fine says:

    The best solvent I have found for this application is E85 ethanol/gas sold for flex fuel vehicles. It is scary how well it dissolves 50 years of varnish coating on the inside of the tank.

    Disposal is another issue. There used to be torches that were made to burn gas, but I wouldn’t be surprised if the legal industry put an end to that business. The stuff burns well, but the flames are very hard to see in any daylight so be carefull. And yes the fumes are explosive.

  5. Jordan Heath
    Jordan Heath says:

    Beware “boiling out” the tank often involves chemicals that will remove the original rust proof finish inside the tank. Get the gunk out by sloshing nuts and bolts with cleaner as noted above and leave it alone. If the original plating is still inside you are good to go. I have never seen any tank sealer that is permanent.

  6. steve bunda
    steve bunda says:

    An old timer told me a trick, pour gravel and a little fresh gas in the tank and slosh and shake it around. Then wash out with gas. Burn remnants in your camp fire ring. I have never done it my self, but this is old school.

  7. reddog
    reddog says:

    Eric. Nice video and real nice job on the way the wolverine project turned out. I have the same gator trail or under my little plywood outboard boat. But mine does not have the little front tire or the spare tire carrier . your resto on the trailer turned out real nice also. Have fun with your boat.

  8. Jordan Heath
    Jordan Heath says:

    I’m not sure about carb cleaner, you could do a small test spot. I know that “carb dip” will remove plating if left long enough. There is no easy fix. It takes the mechanical action of gently tumbling media (nuts and bolts or rocks etc) mixed with a mild solvent to do the job.

  9. Richard Piatt
    Richard Piatt says:

    I just cleaned the Tank in my fathers 1956 Continental that has been sitting for 8 years. Removed the gas and searched high and low of what to do. ONLY thing that actually works is Sodium Hydroxide (Lye) to dissolve sludge. Prior to that I tried everything from Simple Green to Acetone to Vinegar. I actually did a test afterwards by taking equal clumps of sludge in different cups with each of the “Recommendations” Left a solution in tank for a day and 1/2. Neutralized with Vinegar then filled tank with a solution of Phosphoric acid to neutralize remaining rust. Neutralized Acid with a Baking Soda Solution rinsed and dried tank and then coated inside of tank with Wd-40. Simple green seemed to loosen sludge to the point where I could scrape some of it out with a Crow bar. All in all took out about 15lbs of gooey crud.

    • Thom Wiseman
      Thom Wiseman says:

      What rate of sodium hydroxide would you recommend? After removing it do you need to rinse with a small amount of fuel and then discard that?

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