Ethanol and marine engines: Setting the record straight

Editor’s note: The author submitted this post in response to a recent article on the results of a Boating Industry reader survey, “Survey: Ethanol repair issues growing.” All opinions are those of the author. The article has not been edited, except where indicated with “Editor’s note.”

Misinformation and scare tactics about ethanol have once again been ratcheted up in the piece “Survey: Ethanol repair issue growing.” The author ignores the simple truth that E10 is a gasoline used by more than 95 percent of Americans and is safe to use in marine engines. Indeed, all current boat engines are warrantied for E10 and have been for nearly two decades. This information and a myriad of owner’s manuals expressly approving the use of E10 have been conveniently ignored, and instead the author chose to fuel fears of engine failure due to E15, which is not even approved for use in marine engines. The biggest failing of the article, however, is the failure to make any connection between ethanol and engine damage. It regurgitated
a couple of quotes, without a single example of WHAT the damage was. That’s because these false claims don’t exist—all modern day boats are approved to use E10, and boating enthusiasts know what the right fuel for their needs is.

This piece is an attempt to muddy the waters on E10’s safety for marine engines through a push poll and here it fails once more. Given that the author acknowledges that the poll itself found that only 3 percent of respondents knew about the E15, it makes it impossible to believe that 81 percent of those same respondents were “very concerned” about the growing use of the fuel. [Editor’s note: The article states that 3 percent of survey respondents believe that boaters know a lot about ethanol. Sixty-six percent of readers said they know a lot about the issue, 26 percent said they know some and 8 percent said the know a little or nothing about the issue.]

Proper care and maintenance are the best and easiest ways to protect boat engines. While E10 is a safe, reliable fueling option for both marine engines and automobiles, higher ethanol blends, such as E15, are not approved for use in marine engines.

As the owner of CK Motorsports, a premier certified Mercury Marine Engine & Racing service dealer that services 400-500 boats annually in the Great Lakes, and has for over 20 years in Nunica, Mich., I believe it is important to set the record straight when it comes to ethanol and marine engines.

Here are just a few facts and observations I have made over my 20 years servicing marine engines:

  • CK Motorsports does not see these phase separations with E10 ethanol as claimed in several boating industry articles, or special interest hit pieces.
  • Certain companies are rather far-reaching in making claims; knowingly or unknowingly creating consumer confusion surrounding ethanol and its use in marine engines.
  • Ethanol is a clean burning fuel, which is much better for our environment. Put simply, CLEAN AIR, CLEAN WATER, CLEAN BOATING creates less carbon dioxide.

CK Motorsports has found ethanol fuels help marine engines run cooler, run longer and make better horsepower gains.

  • E10 ethanol absolutely IS an acceptable fuel for everyday use in marine engines.
  • When E10 comes into contact with water, the ethanol will allow the fuel to absorb some or all of that water. Additionally, E10 ethanol also eliminates the need for freeze preventers.
  • The primary cause of water collecting in fuel tanks is condensation from humid air.
  • An engine running on E10 can ingest small amounts of water in the fuel without harming the engine.
  • All Mercury Marine engines are warrantied for E10 Fuel.

Finally, it is important that all marine engine owners follow the instructions for normal storage preparation found in the operation, maintenance and warranty manuals. Failure to follow the proper operating procedures is the number one reason why boaters have fuel issues.

The bottom line is that if you have engine troubles, there are many possible causes, and you should not immediately assume E10 is the problem. The facts and my 20 years of experience show that ethanol is not to blame.

It’s time to stop the misinformation and scare tactics – it’s time for consumer choice, cleaner air and improved conservation efforts. That is what CK Motorsports believes in, because ethanol delivers.

Keith Holmes,
President, Owner
CK Motorsports
Certified Marine Technician


  1. I’m glad that you and your customers are not experiencing problems with E10 fuel. Here in Texas, we see problems that are caused by Ethanol in the fuel on a regular basis. In coastal areas with high humidity, we can see phase separation in fuel that sits for 3-4 months. We also see issues where the Ethanol strips the paint off of the inside of the fuel cooling system on Mercruiser Sterndriive power packages. This clogs the fuel system and causes extensive repairs to be necessary. There are many other issues that come up as well. Again, I’m glad that your area doesn’t experience problems, but I believe that you must be in a lower humidity environment, also it is unlikely that boats in your area stay in the water year round. Ethanol problems are alive and well in Texas.

  2. We can all rest assured of one thing, ethanol is here to stay regardless of which side of the aisle you’re on. The fact that marine engine owners are having problems still remains and the most likely culprit appears to be ethanol blended into substandard gasoline to improve that fuel into an operable range. Experts agree, the best way to inhibit the negative effects of ethanol is for marine engine owners to stabilize the fuel with a quality fuel conditioner. Click on the link below to view a video that will provide you with an understanding of what happens when condensation or moisture (a.k.a. water) is present in ethanol blended gasoline and which fuel conditioner is right for you. Hope this is helpful.

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