Boating Thoughts

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E15 fuel & year round sales - Boaters Beware!


The U.S. Environmental Protection Agency (EPA) has said it will complete a proposal to expand sales of higher ethanol blends of gasoline in time for summer.



E15 - It's not for boats!


Motor fuel containing 15 percent ethanol (E15) is prohibited in recreational boats and will void the warranty of marine engines.


Ethanol content was originally capped at 10 percent (E10) but in 2011 the EPA granted a waiver that allows the percentage of ethanol in the nation's gasoline supply to jump from 10 percent (E10) to 15 percent (E15) to be sold only for cars, SUVs and light-duty trucks made since 2001. This EPA waiver does not permit use of the higher alcohol content fuel in lawnmowers, chainsaws, snowmobiles, motorcycles or boats.

Whilst late-model cars and trucks designed to be “flex fuel” vehicles have an engine control system, late-model marine engines (including outboards and inboards) do not have flex-fuel capability. They are designed to operate safely on fuel containing no more than 10 percent ethanol (E10). Older marine engines and boats, manufactured before ethanol was common in motor fuel are often incompatible with ethanol fuels at all.


E15 fuel can damage marine engines in a number of ways.


The fuel may not be compatible with plastic and rubber components in the fuel system, and it may cause corrosion of some metal components.

Ethanol also raises the oxygen content of fuel, which can cause a lean condition and cause the engine to run hot and eventually fail do to excessive carbon build-up, over-heated exhaust valves and bearing failure in older two-stroke outboard engines.

The High Ethanol Fuel Endurance study conducted in 2011 by the National Renewable Energy Laboratory using three Mercury outboard engines revealed the potential damage E15 can cause to these marine engines – the test caused the complete failure of a Verado 300 outboard. (You can find the technical report HERE)


It’s not just the engine that’s at risk. The entire fuel system of the boat, from the hose that fills the tank to the fuel line to the engine, has been designed to tolerate E10 fuel, but no higher percentage of ethanol. E15 and even E10 fuel can cause all sorts of problems in the boat fuel system.


  • Look twice before you pump!Select fuel carefully at gas station pumps and never use E15 fuel in a marine engine. When possible purchase E0 fuel with no ethanol content for marine engines.

  • Use a quality fuel stabilizer additive unless you are certain the fuel will be used in less than three weeks.

  • Install a 10-micron water-separating fuel filter between the fuel tank and the engine, and carry a spare filter element on board (check with your engine manufacturer for the best size filter).


Since the sale of E15 was first proposed the marine industry has been concerned that poorly labelled pumps will make it too easy for boat owners to “mis-fuel.” Protecting Boaters at the Gas Pump is a new website created by the National Marine Manufacturers Association (NMMA) depicting a series of photos of gas station pumps clearly show the challenges boaters face with poor ethanol warning labels at the pump.

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