I installed a clean out port in my fuel tank
last week, and then was faced with a lot of black goop, mold
and such in the tank. Being lazy I decided empty the tank with a siphon, then added 1/2 gallon of a degreaser called B-52, then about 15 gallons of water
in my 33 gallon fiberglass fuel tank
. I let the mixture set for a while then took an air hose with a open end and "blew bubbles" in the mix. I noticed that after 30 minutes the soapy mixture had turned chocolate brown. I drained the tank, rinsed it with lots of hot (from the garden hose) water
. Lo and behold the tank is as clean as the day the boat was built!!! I wiped the tank out with denatured alcohol to remove any traces of water and 25 years of funk were gone! I bought the B-52 degreaser at the local auto parts
store. Sure turned a miserable job into not to durn bad!