What to Know About Using Ethanol Gas in Your Boat or Outboard Motor

One of the most confusing topics in all of boating, pontoon or otherwise, deals with gasoline—particularly ethanol. Can you use it? If so, what percentage of it is okay to use in your boat engine? We’ll try to alleviate the confusion by breaking down the essential points.

What is Ethanol?

Ethanol is added to fuel to diminish pollution. Acting as an oxygenate, ethanol—which is essentially 200-proof grain alcohol—reduces hydrocarbon emissions. We should note that ethanol used for fuel is not safe to drink.

The most common ethanol-blended fuel is E10, which means the fuel is made of 10% ethanol and 90% gasoline. E15 (15% ethanol and 85% gas) has been the source of much debate in Washington, D.C. lately, with the National Marine Manufacturers Association (NMMA) lobbying hard against the sale of E15.

Is ethanol gas bad for boat motors?

Is Ethanol Gas Bad for Boat Motors?

This is where it gets confusing. E15 is not good for boats. Do not put E15 into your boat’s motor. Using E15 in your boat’s motor can cause unfixable damage. You could find yourself with complete engine failure and all the safety risks that come with using a fuel incompatible with your boat’s engine.

However, E10 is good and compatible with all marine engines built in the last 10 years or so. Because a fuel’s ethanol content is not always obvious at the pump, it’s important to make absolutely certain you’re using E10 before filling the tank. This confusion, and the potentially damaging effects of putting the wrong amount of ethanol in your boat, is just one of the reasons the NMMA is so adamantly opposed to the sale of E15.

If E15 is So Bad, Why the Controversy?

The fight is over whether to allow the year-round sale of E15. Because there is more ethanol and less gasoline than in E10, E15 is better for the environment, and proponents also say selling E15 all year would lower prices. Further, a demand for a more environmentally-friendly fuel might help the industry work to produce even better fuels.

Currently, E15 cannot be sold all year largely because it can’t be produced all year. Its fuel volatility in the summer months is too high, leaving too great a risk to produce it.

The NMMA’s worry is that year-round sales of E15 will add further confusion to the issue and potentially lead to accidental and unnecessary destruction of recreational boaters’ vessels. When boaters fill their tanks, they don’t always thoroughly check to make sure their fuel is E10, and one mistake can lead to complete engine failure.

As the NMMA continues to lobby for recreational boaters and the industry, it’s important to know how to keep your own boat safe when fueling.

Fueling Tips:

  • Given a choice between E10 and E15, always use E10. However, certain engines may require other fuels, so be sure to consult your owner’s manual first.
  • Make absolutely certain you’re filling your tank with E10. Check at the pump. It’s easy to make a mistake, as some gas stations will have E10, E15, or even another type of fuel, so double (or triple) check before fueling.