Water in Boat Fuel Not Always Due to Ethanol

Water in Boat Fuel Not Always Due to Ethanol
Badly corroded fuel gauge/sending unit fitting, removed from fuel tank in customer’s boat recently.
Water in your boat's fuel tank and fuel system can be costly to remove and can damage an engine beyond repair if not caught in time. There are basically three ways for water get into fuel and all are preventable.

1). A clean fuel source is critical and knowing the quality of the fuel you're buying sounds obvious but... how do you know? The answer is you don't know but, here's a great tip.

Modern fuel pumps register the amount of fuel dispensed on a digital screen; the one that goes so fast you can hardly read it. A clean and well-filtered pump will deliver one gallon of gasoline in 8 seconds, on average. A pump that runs noticeably slower could be either delivering fuel saturated with moisture or the filter is dirty and contaminated with moisture. STOP PUMPING! Do not be timid in asking how often the pump's filters are changed where you buy your fuel.

2). Ethanol is highly hygroscopic, meaning that it can readily absorb moisture (water) from the atmosphere and this process can begin during fuel transport and storage, before you even purchase it. Once water is in the fuel in any amount it saturates all the fuel rapidly. Using fuel treatment additives is a must–every time, every tank!

3). Perhaps the most overlooked point of moisture entry to fuel systems is the boat's fuel tank itself and this is not always obvious. But a fuel tank with a hole would leak fuel externally and the smell would be obvious, wouldn't it? Not always!

Many boats are built with fuel tanks below decks or under consoles and these are difficult or nearly impossible to inspect visually. Some builders install access ports for inspection and cleaning, but not all. Tanks made with a top surface that is flat will often sag over time, forming a shallow basin. Water from boat cleaning, rain and also condensation from the underside of decks will collect here. Fuel line connections and also fuel gauge sending units are commonly mounted to the tops of fuel tanks, sealed with gaskets, and this is where problems can arise.

Prolonged contact with water, especially water with salt content, causes gaskets to degrade and fittings to corrode. Aluminum fuel tanks are often the worst for this type of failure. We often find tiny holes in the tank itself. With the "basin" catching water, it's a cinch that it'll drain directly into the tank. Never underestimate the power of salt or mineral build up.

Inspect this area regularly or take it to your dealer, especially if you experience frequent clogging of fuel/water separator filters, power loss or rough running, or any fuel related issues.

Preventive maintenance is your boat's best friend. Have a great spring season!

Chris Mapp

Coastal Bend Marine
Port O'Connor, TX