Fuel System Preventive Maintenance
Carbureted Engines:
Fuel deterioration is a significant issue affecting carbureted engines. Current gasoline formulations have a limited shelf life when exposed to heat and air, and can deteriorate in just 3 to 4 weeks. You cannot avoid the problem, but you can prevent it easily and inexpensively.
When exposed to air or heat, the fuel in a caruretor's float bowl begins to oxidize, turning into a varnish-like substance that will restrict or block the carburetor jets. All carburetor float bowls are vented to the atmosphere, allowing the fuel to oxidize at a slow, steady rate.
The gasoline in your boat's fuel tank is also exposed to the air through the tank's vent. To slow the deterioration of gasoline in the tank, keep as much air as possible out of the tank by keeping the tank full during periods of storage. To counteract the deterioration of gasoline, use a fuel stabilizer at the recommended ratio. The amount of stabilizer required varies, depending on how long the fuel will be stored. Follow the manufacturer's instructions listed on the fuel stabilizer container. If you use your boat infrequently (less than twice month), you should keep fuel stabilizer in your boat's fuel tank at all times. Be sure you run your engine in the water, under a slight load if possible, for at least 10 minutes after adding the stabilizer. This allows the stabilized fuel mixture to reach and fill the carburetors.
Even though the oxidation rate and associated carburetor problems are reduced by using stabilized fuel, the fuel can lose its volatility (ability to vaporize and ignite inside the engine). Prior to starting an engine that has been sitting, be sure you refill the caruretors by squeezing the primer bulb several times until it is firm. The fuel from the tank will mix with the fuel in the carburetors and make it easier to start the engine. Check the owner's manual for the correct starting procedure for your engine.
Fuel Injected:
Fuel injected engines are less susceptible to fuel deterioratoin problems than carbureted engines. Fuel injected engines store fuel in a vapor separator, a large reservoir with a float and vent similar to a carburetor. The vent, however, is filtered, so the fuel inside has less exposure to the air and stays fresh longer. Add fuel stabilizer to your boat's fuel tank(s) and run the engine in the water, under a slight load if possible, for 15 to 20 minutes.
