I have read about the horror stories but under 10% seems to be the magic level where only plastic and rubber parts (gas lines and gaskets) alone will be disolved. No boat engine manufacturer will honor any warranty where ethanol mix gas is used. All marine gasoline is Federally exempt from the ethanol addition requirement. My first hand experience consisted of my son-in-law borrowing my boat and filling the 30 gallon tank with gas station gas. I didn't take the boat out for a couple of months and when I did I checked the water filter and found over a pint of water. Ethanol absorbs water like crazy from the environment. Think of it as adding a pint of water to every tank of gas. I guess if you live in desert areas you would only have to worry about the plastic/rubber/seals problems. If I could only find E-15 I would put a marine water filter (they look outside just like an
oil filter) on my cars. Don't even get me started on how this fraud was perpetrated by the Government and special interests for the corn growers, on the general public.