Ethanol Gas in Watercraft.
Phase Separation describes what happens to gasoline containing Ethanol when water is present. When gasoline containing even small amounts of Ethanol comes in contact with water, either liquid or in the form of humidity; the Ethanol will pick-up and absorb some or all of that water. When it reaches a saturation point the Ethanol and water will Phase Separate, actually coming out of solution and forming two or three distinct layers in the tank.
When this Phase Separation occurs you will have an upper layer of gasoline with a milky layer of Ethanol and Water below it, and then in many cases a third layer of just water at the bottom.
If this happens and you try to start the engine you can have one or more of the following problems. If your fuel tank pick-up tube is in the water layer, most likely the engine will fail to start. If the engine is running and suddenly draws water you can have damage from thermal shock or hydro-lock. If the pick-up tube draws the Ethanol-Water mixture or just Ethanol you can have problems where the engine will operate in an extreme lean condition, which can cause significant damage or even catastrophic failure. If the pick-up tube draws the gasoline, it will operate very poorly due to lower octane that is the result of no longer having the Ethanol in the fuel. There are several gas treatment and additives that are offered at local auto parts stores and retail chains for ethanol treatment. The truth is none of these products fix the issue. They do help but only partially. The best gas treatments only remove or reverse phase separation by a percentage!! the only real cure or treatment is with periodic maintenance. All Watercraft will have moisture if not water in the fuel system. It is more common than not to have Watercraft maintenance issue from water ingestion and old gas. By cleaning your fuel system annually this will help prevent issues. Removing gas while storing your Watercraft during the off season will help along with additives. There is no magical cure in a bottle once moisture and water are present. The fuel system will have to be drained and cleaned!!!
When water is ingested into the carburetors on your Watercraft it will remain inside the carburetor until manually removed (cleaned). Adding alcohol or gas treatment to the fuel will not remove the water.