Fuel tank cleaning

[DArcy]

Any suggestions for how to clean a fuel tank? The tank is gasoline, I have an Atomic 4. This spring it was very rough idling so I dismantled and cleaned the carburetor. There was a lot of gunk so I put in a new fuel filter. After a couple of hours of running it was running rough again so I took out the fuel filter and it was full of crud again.
The tank appears to be in excellent condition from the outside. It is 44 years old, made of monel. I'm pretty sure I cannot remove the tank without cutting up a cockpit locker but the top of the tank is easily accessed, including the inlet hose and the cap for the fuel sender. The capacity is 20 gallons and it is about 1/3 full.

 

[capta]

If you can access the whole tank from a hole in the top, like the fuel sender opening, and there are no baffles, you can get someone in to clean the tank and it will be a good job. However, if there are sections behind a baffle that cannot be directly accessed, those sections will not get nearly as clean.
I would not recommend you do this one yourself, as gas is very combustable so the job is better left to a professional.

 

[Rick D]

I did this on a pontoon boat using an electric fuel pump into a very large filter (diesel truck) and using copper "wands" made from hardware store tubing attached to fuel line. I used the sending unit to access. I wasn't thrilled doing it but note that it was on a pontoon boat with open air. FWIW