It plays hell with small engines, too. I don't understand all the chemistry, but apparently ethanol is hydrophilic, or something like that, and helps build up moisture in the fuel. There are additives that do a good job of reversing the effect.
First, once ethanol has absorbed any moisture, there's no product on the planet that'll reverse the effect.
Second, while ethanol is hydrophilic, it doesn't grab moisture out of the air and absorb it, contrary to the hyper scare-isms floating around. Ethanol will, on the other hand, absorb the water that condenses in the fuel tank during its daily heating/cooling cycle. That's where the water gets introduced.
Third, ethanol has been around for over 20 years. True, if you haven't put alcohol resistant fuel lines and/or gaskets in your engine (think outboards and small engines), you will have a problem. But once that's done, very little problems are created IF you follow a couple of common sense precautions with ethanol-laced gas.
Ethanol-laced gas can and will oxidize rather quickly, leaving very low octane gas behind. This is why you use a stabilizer in gas that'll sit for extended periods of time in cans or the gas tank. Lots of people with outboards and/or small engined equipment (mowers, chain saws, etc.) fail to understand this and act upon it. Left sitting for months, you end up with something akin to 80 octane gas when the ethanol converts to worthless liquid and the engine runs horribly, if at all, and can gum up the carb. Stabilizers, such as Seafoam and StaBil, prevent ethanol from degrading, so your gas stays "fresh".
This was taken from a webinar put on by Mercury Marine and talked about ethanol myths, which included the "water absorption" myth:
MYTH: E10 Gasoline pulls water directly out of the air:
–There is no active transfer mechanism for ethanol molecules to reach out and “grab” water molecules out of the air. Under normal storage conditions, even in a vented fuel tank it just does not happen at a level or rate that is relevant.
–The primary cause of water collecting in fuel tanks is condensation from humid air. This water runs under the fuel and collects in the bottom of the tank. The volume of air that can move into the tank is reduced when the tank is kept full.
And during the webinar, Mercury also said this:
After the transition period from E0, E10 may actually be a superior marine fuel as it tends to keep low levels of water moving through the fuel system, keeping the system “dry”.
And remember, there's no bottle of anything that can reverse ethanol problems, esp. with oxidized gas. Then again, don't always assume the problem is with ethanol.
Heck, I've been running boats for more than 30 years of all sorts of vintages and have yet to have the dreaded ethanol problems. Of course, I do keep my gas tanks full, treat with a stabilizer, and use alcohol resistant fuel lines.