Problems With an Outboard Carburetor

A small, low horsepower outboard engine can propel a dingy or fishing boat. If not properly maintained, the engine carburetor can become clogged, preventing the engine from starting. Fuel and moisture issues can also cause starting problems. The carburetor is essential for the operation of a combustion engine.

  1. Old Gasoline

    • Fuel is the lifeblood of every combustible engine. While automobiles are typically used daily, outboard motors may sit for weeks without being started. Gasoline left in fuel tanks for extended periods of time will clog a carburetor. The light molecules evaporate and leave behind thick, sticky residue that will clog a carburetor and prevent the engine from starting. The carburetor on an outboard motor is small and contains jets and hoses running to the engine. Only a small amount of residue can gum up the component.

    Fuel System

    • Debris and dirt introduced into the gas tank will find its way to the carburetor and clog it. Keep fuel containers capped to prevent dirt from getting into the gas can. Storing the engine incorrectly can also cause carburetor problems. If tilted or laid flat, fuel can drain from the carburetor float-bowl, where the reserve fuel is kept, making it difficult if not impossible to start since the engine will not be primed with fuel.

    Ethanol Gas

    • Since the widespread distribution of ethanol alcohol gasoline began in 2006, boat owners have seen an increase in engine and carburetor problems. Ethanol gasoline should not contain more than 10 percent alcohol. Most engine manuals for outboard motors warn against using more than 10 percent alcohol in gasoline. But often the percentage is mixed incorrectly at the fuel stations, causing carburetor vapor lock where too much water is pulled into the engine. Alcohol absorbs water, so the more alcohol in a tank, the more water it will absorb. If left to sit without starting, ethanol fuel will separate, with the water and alcohol sinking to the bottom of the tank. It will then be picked up by the fuel system, injected into the carburetor, preventing the engine from starting.

    Fuel Filter, Battery and Spark Plugs

    • All the components of an engine need to be in good working order for the engine to operate efficiently. A dirty fuel filter can inject dirt into the carburetor and block the lines and hoses. The battery and spark plugs also need to be firing correctly to start the engine and keep it running.