Cleaning a fuel tank in boat

It appears as though I need to completely clean my tank. It's an 80 gal aluminum, and I don't think I can (easily/realistically) get it out without it becoming a major project. I've searched and read through post relating to this, and this is what I've gleaned from those;

1) there is nothing I can add to break down the 'shellac' so it will run through without clogging

2) denatured alcohol will clean the gunk off

3) rocking the boat with the tank full of nuts and bolts will expedite the process

4) 'polishing' the gas (cycling through filter(s) multiple times can clean up the gas and make it usable (it's fresh non-ethanol)

5) run it as is, and change filters after about every use

6) hire a tank cleaning company

7) don't use a shop-vac

8) use a stick with a rag

So from this info (and more), if I want to do this myself, I could drain the tank, and put in some denatured alcohol. First question is, how much denatured alcohol would I want to use? 1 gal? 5? 10? 80? After I do that, and then drain the denatured alcohol, can any residual alcohol be left in the tank, or do I need to let it evaporate out?

Is there a better way, or a way you would do it, without removing the tank from the boat?

Re: Cleaning a fuel tank in boat

So nobody has any suggestions for cleaning my tank while it's still in the boat? Hmmm....

Re: Cleaning a fuel tank in boat

I faced the same challenge. I called three radiator shops in my market; the first one was real vague, the second one indicated that he charged by the hour ($35) and the third one stated "been in this business over 30 years and boiling it clean will not work." So there I was....nothing I could do to clean it out.....I had the boat deck opened up so I could take the 44 gal take out and take it to the shop..... but thoses guys where telling me " lots of money and no guarantee it will be successful." OK....so here I am in Columbus, OH with maybe 16 to 20 weeks of boating weather....less the weekends when I have other obligations.....so when I want the boat to go....I want it to go! Bit the bullet...called the original tank manufacturer (there was a mfr. plate on the tank)....got a price with shipping that I could live with....$450. ....about 4 weeks later I had a new tank! Since then I've never a problem with the boat not running! Sorry, wish I had an easier solution for you. Good luck.

Re: Cleaning a fuel tank in boat

I read on another thread to drain the tank and then put about 1 gallon of methyl hydrate in and let it sit about 24 hrs. Apparently it is supposed to break down the shellac. For want of any other information, I did this and let it sit for 48 hrs. However, I have not yet replaced the gas and started it up yet.

Draining was a problem - even though my tank is only about 6 gals, it is not easily removable. Bought a hand pump from Princess Auto with one intake hose and a second outlet hose - each 3/8" vinyl. Lots of suction but the O-ring at the end of the pump trickled gas on the down stroke so had to have a catch-can to pick it up.

I changed the vinyl suction hose to a 3/8" air hose and this worked great . The weighted nozzle on the hose went to the bottom of the tank and found the low corner so I'm pretty sure most all of the gas was drained out.

The leaky pump was a nuisance so returned it and bought a higher capacity rotary barrel pump. Now have to find some reducing couplers to get from the 1" threaded pump pipe down to 3/8" so I can use the air hose. I'm pretty sure this will work. What little old boat gas/methyl hydrate is left, "they" tell me it will burn off with the new gas. I hope "they" are right.

Re: Cleaning a fuel tank in boat

Ever heard of 44k? You can get it at auto dealerships (not parts stores) try running a few cans of that through it. It cost about 20 bucks a can but its liquid gold!!!

Re: Cleaning a fuel tank in boat

Since I can't call anyone until Mon or Tues, I've decided I'm going to try and polish what's in there. I have a fuel siphon pump, and a new fuel filter that I've had sitting around from a car I don't own anymore. I'm thinking I'll rig a setup where I pump the fuel through that filter, and back into the tank. I'd suction from the pick-up end of the tank, and return through the sending unit access. I may end up going through more then one filter, and it'll probably take a couple of hours, but, hey... it's something to do. I'll probably try to get the fuel level down to about 10 gallons, and add a fuel system cleaner, and pump away. If I'm lucky, it'll get most of the crud out, and then I can run the boat and change all the filters (again ). We'll see....