Yamaha Marine

What are the negative properties of ethanol?
A. Ethanol has several properties that contribute to fuel system issues.
• Ethanol is a strong cleaner (solvent).
• Ethanol is hygroscopic (e.g., it has a strong attraction to moisture).
• E10 fuel’s usable life span may be less than the normal length of off season boat storage.


Why do boats seem to have more issues attributed to E10 fuel than cars?
Cars are having issues but are somewhat more tolerant due to typical usage patterns and differences in their fuel systems. Major differences are:
• Modern automotive fuel systems (fuel filler, fuel tank, distribution lines and engine components) are closed or non-vented. Once the fuel is pumped into the tank, there is very little circulation of outside air (containing moisture) into the fuel system.
• Boats are operated and often stored in a very wet environment increasing the risk of water directly entering the fuel system.
• Boats have vented fuel systems which allow moisture laden air to circulate into the fuel tank as the fuel is drawn out of the tank and as the fuel expands and contracts during heating and cooling cycles of the outside air.
• Automotive fuel tanks are typically much smaller than boat fuel tanks and are refilled more frequently. A full tank of fuel in a car or truck, typically 20 ~ 40 gals, may be used and refilled every week or two. Boat fuel tanks, typically 40 ~ 100+ gals per tank, may only be refilled once a month during the boating season and typically may sit unused for many months during the off season.
• Some boats use fiberglass fuel tanks. Polyester resins can be dissolved by ethanol.


How long can E10 fuel be stored?
There are many different opinions concerning how long it is ok to store any fuel (E10 fuel or gasoline), 2 weeks, 90 days, 1 year, or longer, before losing the properties that are required for proper and safe operation of your engine. There are too many variables (e.g., the age of fuel when purchased, temperature, humidity, use of stabilizers and the type of storage containers) to accurately predict how long.


What can I do to prevent issues with E10 fuel?
Total prevention of issues may not be possible but there are steps you can take to minimize the occurrence and severity of the negative affects of E10 fuel:
• If at all possible, do not use E10 fuel.
• Ideally (before switching to E10 fuel) have your fuel tank completely drained to remove any accumulated water. As little as 16 oz. of water can promote phase separation in 25 gals of E10 fuel. The result would be 2.75 gals of unusable ethanol and water mixture on the bottom of the tank.
• If the tank can be completely drained, the internal surfaces should be mechanically cleaned to remove rust or aluminum oxides. Fuel polishing companies may be able to provide this specialized service.
• Consider replacing the fuel tank in an older boat.
• If your boat has fiberglass fuel tanks built prior to the early 1990’s, consult with your boat builder concerning E10 compatibility.
• If unable to completely drain and clean your tank before switching to E10 fuel, add as much E10 fuel as possible to minimize the possibility of phase separation. Example: 16 oz of water may cause phase separation in 25 gals of E10 but 16 oz of water in 30 gals would be safe from phase separation.
• Install a Yamaha 10-micron water separating/fuel filter between the boat’s fuel tank and the engine.
• Change the 10-micron filter every 25 hours of use until there are no indications of excessive water and contaminates collecting in the filter. Normal filter changes are recommended every 50 hours of use.
• Carry extra filters and change more frequently if there are indications the efficiency of the filter is rapidly diminishing due to excessive water and contaminates.
• Do not drain a used filter and reinstall. Contaminated fuel can enter the filtered side of the filter while draining.
• Buy name brand fuel.
• Buy fuel from the same source if possible.
• Buy fuel from stations that have newer, cleaner storage tanks.
• Occasionally, test your fuel to verify the amount of ethanol is not higher than 10%. The blending of ethanol with gasoline by distributors is not a precision process. Inexpensive test kits are available, GOOGLE E10 Fuel Test Kit.
• Regularly use Yamaha Fuel Stabilizer to retard fuel aging.
• Stabilize fresh fuel before storing. Stabilizers do not help fuel that has already aged. Stabilizers are most effective when immediately added to fuel fresh from the gas station or marina fuel pump