Contaminated fuel tank – the hull truth – boating and fishing forum electricity transmission loss


Here’s my story for today. I redid my 18 foot Privateer, completing the project back in 2014. New fuel tank (from SP Sheet Metal), new deck, raised transom 20" to 25", Awlgrip paint. Everything came out real nice and I really enjoy the boat. It is a little small for the ocean and more than say three or four people at a time.

I have a Parker 23SE that I bought new as a bare hull back in 1988. It was repowered in 2002 with a Johnson 150 HP two stroke. It’s not a heavy boat and this is plenty of power. It has sat in the water in NJ for the past five years and a few months ago I hauled it out and had the motor totally gone over by Wally at Off-Shore Outboards in Jackson, NJ. Compression tested as new in all cylinders and Wally says there is a lot of life left in this engine.

Only problem is the fuel in the 95 gallon fuel tank is contaminated. From what I can see of the tank through the inspection hatches I am reasonably confident that the tank itself is still good. The point of this post is to get some input and advice on how best to clean the tank to the point where it will be ok to use and not cause me problems.

I did’t know how much fuel is in the tank and when I got a siphon flow going it stopped at about 8 gallons removed. I couldn’t get the flow going again. The gas that cam out was definitely contaminated and discolored and a gallon put in a milk jug had a clear separation line. I put 5 gallons of fresh gas in and was able to get the siphon flow going again and got about 4.5 gallons out. This time it came out clean with no separation line in the sample I put in a clear container.

Someone suggested I buy a 12 volt transfer pump and attach a length of copper tubing to it and suck everything out. This sounded like a good idea until a plumber friend of mine said to never do this because of the risk of creating a spark with the copper tube. I like the boat a lot but I don’t want to kill myself or anyone else messing around with the fuel tank.

I’m thinking that I could keep cycling 5 gallons of fuel at a time through the tank, filtering it each time. If I go this route is there something I could add to the gas to make it pick up water and bring it out of the tank as I siphon the fuel out.

Have you tried forcing the tank contents with a gentle injection of compressed air? I have done this quite a number of times. Get the boat inclined so the pickup point is at the lowest end, then find your breathers. With luck, you’ll be able to access them. You need one for air injection, plug any others. leave your fuel cap on. GENTLY introduce compressed air with a tapered air nozzle through the breather. You will obviously have the fuel outlet line in a suitable size container, you won’t need a primer bulb in the circuit. Give it just enough air to get the fuel flowing freely, top up air pressure as required. This works much better than siphoning . You will be looking at about 2 PSI tops.

Something we use for contaminated fuel in Australia is methylated spirits. I believe you call this de-natured alcohol. This will mix with water. No use for massive contamination, but has long been a fix for tropical boats that suffer from a lot of condensation and subsequent water contamination in the tank. It mixes with water and is then more combustible.