Re: Ethanol added fuel
Most E10 is actually closer to 20 or 25% ethanol. The biggest problem we had here when it came out about 4 years ago was it loosening up all the crap in people's older tanks, and as was mentioned you just need to go through a couple of fuel/water separator filters and once your tank is cleaned out your fine.
Ethanol doesn't add any moisture to the tank, it just sucks the moisture up and combines with it, which will in turn cause the fuel to separate, but it has to sit for a while for that to happen, and if your boat is sitting that long you should be stabilizing anyway.
There is a product out called Startron that eipeldau mentioned above. This product helps keep the Ethanol from combining with any moisture and helps keep the fuel from separating, I use it whenever I get fuel as cheap insurance, it's $12 a bottle but one bottle will last you a couple of tanks. Plus it helps you burn any crud that is going to come out of your tank that the Ethanol will loosen up, and it's a biocide that helps to keep anything from growing on the bottom of your tank when any water accumulates down there. It has been around for Diesel engines for a while, but they now have a Gas version.
All in all I haven't had many problems at all with any of my motors and ethanol. Except for some slight problems with the stuff in the tank loosening up, and that was solved after changing filters one time. You really shouldn't running anything without a fuel/water separator.
You should be fine.