First of all, like most current political thinking, it is flat out stupid to base an energy policy of making fuel out of food.
More important to boaters is that Ethanol will pull water out of the air, and into itself, so it makes for a very bad boat fuel. It is also real hard on some plastics and rubber found in older cars, boats, engine systems.
Right now most gas with ethanol added is about 92/08 percentage wise but field testing at the pump shows this to vary wildly. It was recently voted by Congress to up that gas vs. ethanol ratio to 85/15.
I gotta run now but the info is out there and easily found.