This is from Themarinedoctor
"This past year at service school, I was privy to learn about Mercurys View with regards to Ethanol in fuel.
Here goes. <---gonna skim through it.
Mercury remains very active in developing a thorough understanding of important issues and environments in which our products must operate.
What are ethanol and ethanol-blended fuels?
Ethanol for fuel is highly refined beverage(grain) alcohol, approximately 200 proof, that can be produced from natural products such as corn, sugarcane and wheat. This alcohol is denatured and NOT safe to drink.
Does Ethanol afffect horsepower or fuel efficiency?
Ethanol has a heating value of 76000 BTU per gallon, which is approximately 30% less than gasoline's heating value. The result is E-10 or 10% Ethanol blended fuel should yield slightly lower MPG...roughly 3%.
The octane rating of pure ethanol (200 proof) is about 100 and is therefore useful in elevating octane value of gasoline. In E-10 blends the presence of ethanol provides abaout 2.5-3% of the overall octane rating. The effect on engine horsepower is determined by the octane result of the blended fuel.
Are Mercury engines compatible with ethanol fuels?
The fuel system components of Mercury engines will withstand up to 10% alcohol content in gasoline.
E20 is NOT acceptable in Mercury product.
E85 can cause engine damage in current Mercury products.
What about fuel system components on boats?
Check with your boating manufacturers with regards to acceptable fuels. Fuel tanks and lines may be suseptable to damage from E10 and higher. This may cause clogged filters or leaks or engine damage.
How does ethanol affect fiberglass fuel tanks
Prior to 1991 fuel tanks may NOT be compatible with E10 or greater blends of fuel. Resins can be drawn from the fiberglass and distributed through the fuel system.
Are older fuel lines and gaskets prone to failure
During the 1980's, many rubber components for use in t fuel systems were developed to withstand exposure to fuels containg ethanol. If rubber components in a fuel system are suspected to be of this vintage or older its advisable to replace them. Watch for swelling or deterioration.
Now what everyone worries about...Phase separation and how to deal with it
If signifigant amounts of water are present in a fuel tank with gasoline that contains ethanol, the water will be drawn into the fuel until the saturation point is reached for the three-component mixture of water plus gasoline plus ethanol. Beyond this level of water, phase separtion could cause out of the ethanol and water to separate from the build fuel and drop to the bottom of the tank, leaving gasoline with a signifigantly reduced levle of ethanol in the upper phase. If the lower phase of water and ethanol is large enough to reach the fuel inlet, it could be pumped directly to the engine and cause significant problems. Even if the ethanol water phase at the bottom of the tank is not drawn into the fuel inlet, the reduced ethanol level of the fuel reduces the octane rating by as much as 3 octane numbers...this may cause engine problems.
The level at which phase separation can occur is determined by a number of variables, including the amoount of ethanol, the cmpsition of the fuel, the temperature of the environment and the presence of contaminants. It is VERY important that:
The system is inspected for signifigant quantities of water in the tank before using gasoline with ethanol.
To limit exposure of the fuel tank to excess water.
If phase separati0n has occurred, it is necessary to completely remove all free water from the system and replace the fuel before continuing operation. Otherwise, engine problems can occur.
Are there additives to combat phase separting or to reverse the process?
No
Is there a way to limit the condensation in the tank?
Keep the fuel tanks as full as possible, this will limit the amount of air and tank space above the fuel which may lead to condensation.
The Marine Doctor"
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