Making a Difference On the Water

There are many variations when it comes to fuel systems in boats and other small recreational vehicles. There’s no denying that mid-level ethanol blends are not suited for certain engine types. This is not necessarily due to material compatibility, but instead to the lack of a computer and sensors in those engines to control fuel and air mixture. This is why Fueling the Truth recommends only using up to E10 in your boat.

However, the common assumption that ethanol is a damaging, inefficient or unclean fuel is incorrect. In fact, the website West Marine says E10 may actually be a superior marine fuel. It tends to keep low levels of water moving through the fuel system, keeping the system “dry.” For over a decade, marine engines have been engineered to handle E10 gasoline.


  • What ethanol blend can I use in my boat?

    This site recommends consumers only use up to E10 (regular gasoline) unless E15 is allowed by the manufacturer. This is not necessarily due to material compatibility, but instead to the lack of a computer and sensors in boat engines to control fuel and air mixture.

  • What’s the best practice for winterizing your fuel system?

    Opinions vary on how much to do before storing your boat for the winter, so it’s best to follow your boat’s owner’s manual or talk to your mechanic. However, if you don’t fully drain your fuel system or top it off, storing your boat with some gas not only allows moisture in the fuel tank, but can also allow oxygen in during heating and cooling throughout the day. Since most modern boats don’t have evaporative emission control like automobiles, the increase in oxygen and moisture can be problematic.

    It’s also recommended to have your boat checked before taking the first trip of the season. Additives can be useful, but use caution because over-usage may lead to gumming issues in the fuel system.

  • What do I need to know about phase separation?

    Phase separation occurs when water enters a tank that contains an ethanol/gasoline blended fuel. This can happen in your boat, but preventative measures are available to limit the potential issue. Additives can help increase water absorption but won’t totally eliminate the problem. Filters are also an option to remove small amounts of water and provide an extra level of protection.

    Some additives may claim to prevent phase separation, but that is not correct. Additives may extend the amount of moisture that can stay suspended in the fuel, but no additive can completely avoid it. Storing your boat with a full tank of fuel can help reduce sour gasoline. Please talk to your local boat mechanic for more information.

  • What are the problems of having water in your fuel system?

    Having an occurrence of phase separation will cause the engine to run extremely rough or stall and the fuel system will need to be drained. Consumers should seek a qualified mechanic if not familiar with their fuel system.