E15 is spreading. Keep it out of your boat

October 1, 2026

Where E15 stands

E15 is gasoline blended with up to 15% ethanol. Most pumps still sell E10, which every modern marine engine is built to handle. E15 is usually a few cents cheaper and is turning up at more stations.

This year it was sold all summer, everywhere. Normally E15 can't be sold from June 1 to September 15 because of federal summer volatility limits. In March, EPA issued an emergency waiver that allowed nationwide summer sales starting May 1, and then kept renewing it. It was the fifth straight year of emergency summer waivers.

Congress is now moving to make that permanent. The House passed a year-round E15 bill, H.R. 1346, in May. On September 16, the Senate Agriculture Committee voted 12-11 to advance its farm bill, which includes year-round E15. The full Senate is expected to take it up after the November elections, and the two chambers would still have to agree on a final version. It is not law yet.

None of this changes one rule: E15 is not allowed in boats.

What the law says about boats

EPA approved E15 only for 2001 and newer cars, light trucks and SUVs, plus flex-fuel vehicles. It is not approved for boats, motorcycles, snowmobiles, heavy-duty vehicles, or any lawn and garden equipment. Using it in those engines is prohibited by federal law, and the manufacturers' warranties generally follow the same line.

That is why every E15 pump must carry an orange-and-black EPA label. It says to use the fuel only in 2001 and newer passenger vehicles and flex-fuel vehicles, and not in boats or gasoline-powered equipment.

Why your engine cares

Marine engines are designed and emissions-certified around E10 or less. More ethanol means more oxygen in the fuel, which makes an engine run leaner and hotter than it was built for. Older fuel hoses, gaskets and fiberglass tanks can also be harmed by higher ethanol content. Engine makers and NMMA cite stalling, corrosion, fuel leaks and valve damage as the risks.

Then there is water. Ethanol absorbs moisture from the air, and a boat's vented tank breathes damp air all season. Once the fuel holds more water than it can carry, the ethanol and water drop out together to the bottom of the tank. That is phase separation. The engine then pulls in a water-ethanol mix from the pickup, and the gasoline left on top has lost octane. More ethanol in the blend does not make this go away.

What to do

Read every pump, every time. E15 is often sold from the same dispenser as E10, on a separate button. Look for the EPA label and the "E15" or "Unleaded 88" marking. If in doubt, choose another grade.

Prefer marina fuel or ethanol-free gas. Most marina docks sell E10 or ethanol-free. Ethanol-free is widely available on the coast; apps and sites list stations.

Never fill from a blender pump without checking. Some stations sell several blends through one hose. A little leftover E15 in the hose matters less to a car than to a 3-gallon outboard tank.

Treat fuel for storage. As boats come out this fall, add a marine fuel stabilizer, fill the tank to about 95% to limit air space, and change the water-separating fuel filter.

If you misfuel, stop. Don't run it. Have the tank pumped and the system checked. It costs less than an engine.

Your owner's manual lists the fuel your engine is approved for. Check it once, then check the pump label every time you fill up.

Sources

epa.gov — EPA: E15 approved for 2001+ cars, light trucks and FFVs; not approved for boats, snowmobiles, motorcycles or nonroad equipment
epa.gov — EPA misfueling rule requiring the E15 pump label
nmma.org — NMMA on the 25 Mar 2026 EPA waiver; "E15 remains prohibited for marine use"
everycrsreport.com — CRS: 2026 emergency waivers; House passage of H.R. 1346 (May 2026); S. 593; court ruling that only Congress can authorize year-round sales
growthenergy.org — Senate committee advanced year-round E15 on 16 Sep 2026; still needs Senate floor, reconciliation with House, signature
naco.org — Farm bill passed committee on party lines 16 Sep; floor vote expected after November elections
nmma.org — NMMA position on year-round E15 and misfueling risk to boaters