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How To Prevent Fuel Contamination

fuel contaminationWe are getting ready to do a passage up North and since we had Zuri laid up for 9 months last summer in Florida and have not sailed much since, we knew that we would have to check the fuel in the tanks for contamination. Because we had a million things to take care of before we left on our road trip in April 2013, I have to confess that we were not as diligent as we should have been about preparing Zuri for a long lay-up and one of the things we did not do was top off the diesel tanks.

After we took Zuri out for a shakedown cruise at the beginning of the season, we realized that there might be water and possibly algae in the fuel after checking our fuel filters. We always check our Racor 500 filters (which have a clear bowl to separate water) before leaving the dock and we found some water and sediment in the bowls that looked like sludge. We immediately called out the fuel filtration guys to clean (polish) our fuel and lo and behold, we had gallons of water and sludge in the tanks. Admittedly, we have not cleaned our tanks in years and we may have taken on contaminated fuel in the Bahamas but even so, it was quite a shock to see just how bad it was.

Why does fuel get contaminated?

fuel filterContaminated fuel from a supplier is not the only way water and dirt gets in your fuel tank. You could have some leaks around the filler cap that is usually mounted flat on the deck where pooling can occur. If the O-ring does not seal properly, it can be the most significant cause for water in your fuel. Water also forms inside the tank as condensation, due to the daily heating and cooling cycles or significant cooling and heating because of weather and the more air in the tank, the more potential for condensation. Fuel tank vent fittings could also be a source for water to the tanks, so make sure that your vents are positioned in a place where water cannot flood the vents. This great article by David Pascoe explains water in fuel.

How to prevent such a costly disaster?

Lesson number one: Don't let your boat sit around for an extended period of time (9 months in our case) with fuel tanks only partly full. (We knew that!) A full tank minimizes condensation of water on the tank's interior wall.

Lesson number two: Diesel fuel left undisturbed for a long period of time is a breeding ground for all kinds of microorganisms, kind of like mold in dark, damp places in your house. These microbes require both fuel and water to thrive, so the more water in the fuel, the more algae will flourish. Therefor, fuel should always be treated with biocide to prevent the growth of microbes.

Lesson number three: It is advisable to clean the fuel tank periodically because no matter how careful you are, dirt, water and microbes do accumulate at the bottom of the tank, just waiting to get churned up in rough and bumpy conditions and clog up your fuel filter, starving the engine of fuel causing the engine to cut out...of course always at the moment critique! How to keep your fuel tanks clean by Capt. Richard Thiel.

See our article on marine engine maintenance tips.

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