Sta-bil makes one just for boats that may have ethanol problems.
I belong to a boating forum called
http://www.boatered.com/forum/, not a fishing forum.
They have a lot of discussions and issues on there about ethanol.
There are always some salesman pushing their spam, but overall, it has some good discussion on ethanol in boats.
I am more worried about it on my old Chris Craft. It is old and the ethanol can eat up a lot of older engine parts and hoses that are not designed for it.
Ethanol will also clean out the tanks and hoses and that will plug up filters.