Originally Posted by Au551e
As i understand it, the ethanol fuels degrade more quickly leading to a drop in octane. In a car that's not a big issue as the fuel is used fairly quickly, but in boats the fuel generally sits longer.
If that is the case, we will have to go boating more often
The biggest worry here has been phase separation (i.e. the alcohol separating from the gas, usually due to high moisture absorbtion.)
The alcohol is added to gasoline as an oxygenator and an octane booster (not octane per se, but an octane rating booster; it retards the explosiveness of the fuel/air mixture.)
Should phase separation occur, your motor sucks either watery alcohol (which a: doesn't burn well, and b: doesn't mix well with 2-stroke oils), or you get straight gas (which no longer has the octane booster, and tends to combust too easily causing detonation problems.)
That said, I haven't heard too many instances of engines being damaged by either. Haven't really been looking for it though.