Join Date: Aug 2006
Location: Arlington, VA
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If you have inspection ports on the tanks and physical access, you can also empty the tank, remove the ports, and scrub it by hand.
Get it as clean as you possibly can, THEN do the fuel polishing thing. Properly done, fuel polishing nozzles are moved around the tank, squirting fuel on the tank walls during the polishing process. This helps to clean the tank walls, as diesel fuel itself is a fairly decent cleanser.
Thereafter, the biocide or other additive is a good idea, but the real solution is to install a fuel polishing system integral to the boat. Not hard to do, and it makes light work of keeping the fuel clean.