Hi All, new to the forum and not a boat owner but, I am a fuel guy and a chemist with an interest in this topic. So I hope you don't mind if I add a couple cents to the discussion hopefully without adding fuel to the fire. ;-)
Ethanol is a cheap octane booster but it's not ideal as a gasoline blendstock for several reasons:
1. The molecule contains 35% oxygen. This leans the fuel and reduces the energy content vs gasoline by 30%.
2. It is hygroscopic which means it has high water affinity. When E10 is exposed to water, ethanol will concentrate in the water phase. This reduces the octane in the gasoline and generates a water-ethanol mixture. If that water ethanol mixture gets in your engine, it will burn very hot and can destroy it. The sub-octane gasoline can also cause knocking in some engines and damage the pistons.
3. Ethanol is corrosive and will oxidize over time to acetic acid, which is very corrosive. This must be avoided to prevent metal corrosion.
4. Ethanol is a good solvent for plasticizers and it swells gaskets and hoses. This can cause fuel leaks over time and damage to elastomers.
Some of these problems can be engineered around with additives to reduce the risk of phase separation and metal corrosion. This requires addition of surfactants, corrosion inhibitors and biocides. Others, like over-leaning and lower fuel efficiency, cannot. The NMMA and DOE sponsored a study comparing E0 to E15 in marine engines. E15 ran a lot hotter and reduced the engine's lifetime significantly. You can read the study here: https://www.nrel.gov/docs/fy12osti/52909.pdf
Most engine manufacturers recommend ethanol-free gasoline for these reasons. Can you run E10 in your engines? Sure, can you leave E10 in your tank and engine between seasons? Only if you add a good stabilizer package. Is it better to run ethanol-free gasoline in marine engines and seasonal off-road equipment? Most assuredly.
Ethanol is a cheap octane booster but it's not ideal as a gasoline blendstock for several reasons:
1. The molecule contains 35% oxygen. This leans the fuel and reduces the energy content vs gasoline by 30%.
2. It is hygroscopic which means it has high water affinity. When E10 is exposed to water, ethanol will concentrate in the water phase. This reduces the octane in the gasoline and generates a water-ethanol mixture. If that water ethanol mixture gets in your engine, it will burn very hot and can destroy it. The sub-octane gasoline can also cause knocking in some engines and damage the pistons.
3. Ethanol is corrosive and will oxidize over time to acetic acid, which is very corrosive. This must be avoided to prevent metal corrosion.
4. Ethanol is a good solvent for plasticizers and it swells gaskets and hoses. This can cause fuel leaks over time and damage to elastomers.
Some of these problems can be engineered around with additives to reduce the risk of phase separation and metal corrosion. This requires addition of surfactants, corrosion inhibitors and biocides. Others, like over-leaning and lower fuel efficiency, cannot. The NMMA and DOE sponsored a study comparing E0 to E15 in marine engines. E15 ran a lot hotter and reduced the engine's lifetime significantly. You can read the study here: https://www.nrel.gov/docs/fy12osti/52909.pdf
Most engine manufacturers recommend ethanol-free gasoline for these reasons. Can you run E10 in your engines? Sure, can you leave E10 in your tank and engine between seasons? Only if you add a good stabilizer package. Is it better to run ethanol-free gasoline in marine engines and seasonal off-road equipment? Most assuredly.