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How do I get water out of my fuel tank?

2008 December 1
Dear Boat Doctor,
I did a very dumb and embarrassing thing: I accidentally filled my diesel tank with water. It was a long day on the water, and I accidentally chose the wrong deck fill.

I now have about five gallons of water in my 55-gallon fuel tank. I did this in my home slip, so I have not tried to start the boat or anything-I just crept home in a bad mood.

Bob Wilson
Clearwater, Florida

Dear Bob,
A friend of mine has a great idea to help prevent this mistake, he paints each deck fill cap a unique color-black for waste, blue for water, and red for fuel.

The first thing you need to do is remove the water from the tank. Luckily fuel and water don't mix, and the denser water will settle to the bottom of your tank. I have found the easiest way to pump off water/fuel is with an oil change pump. Simply enter the tank through the fuel gauge sender and probe down to the bottom of the tank. You'll need to remove all water and some fuel, so you need to empty the pump several times-most hold just a gallon or two.

You may find that you need to pump off the water several times as it resettles to the bottom. You should be able to get it all over a couple days. As a side note, pumping off the bottom of the tank is a good maintenance procedure in any boat-any water or growth in the tank will be on the bottom.

I'd also recommend a good fuel additive to take care of any residual water. I have had really good luck with the products from Power Service (
www.powerservice.com , (800) 643-9089), it has several products that would do a good job.