Keeping Water Out of Your Fuel System

If water finds its way into your fuel, it will settle to the bottom of the tank, as it has in this jar of gasoline.

If water happens to find its way into your fuel system, the results are not pleasant—or cheap. In worst-case scenarios, the entire fuel tank may have to been drained of the corrupted fuel and disposed of by a professional.

To eliminate such expensive headaches, here are some ways to keep water out of your fuel tank:

  • Each season, inspect the o-ring on your boat’s fill cap for signs of cracks or brittleness. Replace if necessary.
  • Keep the vent closed on a portable tank when not in use (just remember to open it when you start your engine).
  • Test the integrity of a portable tank by closing the vent and tipping the tank on its side. If fuel leaks out through the cap, gauge, or any gaskets, water can get in.

    This photo clearly shows fuel escaping around the gasket and gauge.
  • Inspect the gasket around the fuel pickup on a portable tank for signs of brittleness or damage.
  • Inspect the fuel vent on the side of your boat. These vents can sometimes get turned upwards or broken off, allowing water to enter the fuel system. Insects can also build nests in the vent opening, which can block fuel flow.
  • If you don’t plan on using your boat for several months, keep the tank topped off to limit condensation in the trapped air (but allow a little room for expansion). The next-best option is to store the boat with a completely empty tank, but that’s not a viable option for most folks.
  • Use the engine manufacturer’s recommended fuel stabilizer and treatment products. They can make a difference—but don’t wait to use them until after you start experiencing problems.
  • Replace your fuel-water separator filter after every 50 hours of use. Don’t reuse the filter once you’ve emptied it.
  • If you suspect water has entered the fuel tank, siphon off some fuel from the bottom of the tank and check it for water. If you detect any, take the boat to a pro to have the tank and fuel system drained.