Is There Water in Your Fuel?

Not long ago most of the repairs done in marine engine service centers involved changing water pump impellers and replacing propeller shaft seals. But times change, and now mechanics see more problems stemming from water entering fuel tanks. With that in mind, here's what you can do to minimize the problem if you use fuel that isn't laced with ethanol. Fuel containing ethanol presents a problem that will be covered in depth in a future "Boatkeeper" article.

The first line of defense is prevention. When topping off the tanks, scrupulously pre-filter every gallon that you pump. The multi-stage Baja Fuel Filter (bajafilters.com), with its special series of mesh screens, weeds out both particulate matter and water at the point of entry. If you see lots of water being kept out, maybe it's time to try a new fuel dock. Your next line of defense is to keep your tank at least 80 to 95 percent full when you expect the boat to be sitting idle for any length of time. This prevents condensation from forming on the inside walls at night, but leaves room for thermal expansion.

Most important of all is to have a fuel/water separator plumbed into the fuel line. Racor's Aquabloc filter media (www.racor.com) is famous for the way it forces water to the bottom of the drain bowl where it can be drained off. Racor claims nearly 100 percent removal of water and solid contaminants. These filters come in different sizes to accommodate both gasoline or diesel engines and any rate of fuel flow. They're suitable for small outboard motors on tenders and personal watercraft as well as for big boats.

Even more effective is a three-stage filter system typically found on larger craft. The primary stage centrifuges gasoline or diesel fuel, causing large particulate matter and water droplets to fall down into the sediment bowl. The second stage's coalescing ring causes the remaining water to form into droplets and fall into the sediment bowl. At the same time this is going on the dry fuel flows upward and onward to the engine. Tip: Twin filters allow the engine to run while draining contaminants from one filter bowl at a time, or even changing a filter element without having to stop the engine or reprime the system.

Should an engine ever display the classic symptoms of water in the fuel ? namely, hard starting and sputtering ? test the fuel for water contamination to establish with certainty that's actually what's wrong. To find out, Marine Development Research offers a product called the Water Probe Indicator that detects water in your gas or diesel fuel tank. If there is any, dose the fuel with an appropriate additive. Drying fuel with an additive eliminates the hassle of disposing fuel at a recycling center. I know a guy who works at a recycling center who treats contaminated fuel, then burns it in his own boat. According to him, he hasn't bought a gallon of gas for years.

Effective water-in-the-fuel additives include MDR's E-ZORB Water Remover and Star Tron by Starbrite, which use enzyme technology. They work their magic by emulsifying the water and suspending it in the fuel so it can flash off in the combustion chamber. Another choice is a fuel stabilizer upgraded to include an ethanol package. This double hit keeps fuel from souring and at the same time prevents water problems.

If all else fails, it's time to turn to fuel polishing (which we'll also cover in an upcoming "Boatkeeper"), which flows the entire tank of fuel through a filtration system and back to the tank, sometimes more than once.