How to clean Fuel Tanks

Reading someone else's thread got me to wondering if any of you have come up with a good method of cleaning out the fuel tanks (without removing them). Chemicals, rinse w ???, etc.

Re: How to clean Fuel Tanks

I couldn't take my tank out because it so big...36 gallons.
So I took out the 15+ gallons of fuel using a siphon hose.

I then used a turkey baster (from the dollar store) with a hose on the end to collect the last drops going into the outlet connection.
Then flushed it out with fresh gas.

My theory, gas would break down anything left over.
Surprisingly, the only stuff that came out was the same amount of gas mixed with some left over oil.

I have a three filter system, screen at the pickup, a water separator/filter and a smaller filter at the engine. I may remove the small filter since it seems to get damaged by the sun.
Don't use anything that will hurt your tank/hoses and don't use any alcohol, ethanol based product.

Re: How to clean Fuel Tanks

1fishbone said:

and don't use any alcohol, ethanol based product.

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On one of my boats alcohol is my fuel.... lol For that boat I drain that tank after every weekend of use. It doesn't have a chance to get dirty.

On my gasoline powered boat I drain them out and rinse with soapy water before using compressed air to dry out the insides. I do this maybe every 5 years.

Re: How to clean Fuel Tanks

With the use of E-10 fuels ........clean tanks are a common free gift. The alcohol in the fuel does a nice job of keeping 2 stoke tanks with pre-mix and 4 stroke non mixed tanks clean.

Re: How to clean Fuel Tanks

just cleaned out my tank this weekend after a 4 week hunt trying to figure out why my boat was sluggish (1st only at WOT, then wouldnt start for a few mins)....

55 gal alum tank was below all the wood i just fiberglassed, i cut a 5"x5" hole in it and drained the tank with an electric fuel pump. the i took a dyegrinder and ran it under water while i cut thru the aluminum. aluminum will NOT SPARK. so put all those myths to rest. the only reason i ran it under water was to keep it from getting too hot.

there was a pile (3 full hand-fulls) of sludge, dirt, sand that was clogging the pickup tube that goes to the fuel pump...i replaced 3 electric fuel pumps, the carberetor, the fuel filter before i realized that this was the problem.

i sealed it back up with a alum plate and sealant and the boat is running PERFECT.

just letting you know, in my case, flushing with alcohol wasnt enough.

Re: How to clean Fuel Tanks

So, you might be smart to inspect the tank contents before deciding what approach to take. Drain & filter the contents. Maybe remove the sender and use a mechanics inspection mirror to see if there is visible sludge. If there is you'll need to either do the wash out method or Oren's method if it's really rotten in there.
Whatever method you use I'd suggest that you filter the removed contents. Filtering the removed fuel will show when the tank is clean and will make it usable again. If it's really filthy run it through a simple funnel filter like a paint filter or paper coffee filter before putting it through a true fuel filter. Filtering the last rinse after the soap & water method will also verify the tank is ready.
Once the tank is done make sure your pickup, antisiphon and fuel supply are clear.

Re: How to clean Fuel Tanks

for in hull tanks, boat on trailer:
drain fuel by disconnecting gas line before the seperator, run the hose out the bilge drain hole; get it syphoning and/or use the bulb.
OPen top of tank at fuel sender; use a rag on a stick to mop out residue
spray a can or two of carb cleaner in the tank. Raise and lower the trailer tongue to swish it around. Mop out with a rag on a stick.

Note--do not count on ethanol fuel to be cleaning your tank. All the stuff it "cleans" ends up on the bottom of the tank, and then clogging everything on its way to your carbs/injectors.

Re: How to clean Fuel Tanks

NHGuy said:

Maybe remove the sender and use a mechanics inspection mirror to see if there is visible sludge. If there is you'll need to either do the wash out method or Oren's method if it's really rotten in there.

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i actually did that first with a flashlight and mirror...there is a baffle down the middle of the V shaped tank and only one small 2"x1" square a few inches off from the center. no clear way to see to the back end of the tank..

i was actually dreading cutting the tank open and it was completely last resort, and i even tried to flush all the gas out and put new in but even then i had no choice...now im glad i did cause i will always have access to it should the problem like this or any other ever happen again...