Boaters are now faced with a serious problem - ethanol fuel. For years, gasoline contained MTBE, an additive which controls the fuel's octane properties. The additive is being phased out, and now much of the nation's fuel supply is a blend of 10% ethanol and 90% gasoline, commonly referred to as E-10 fuel.
Ethanol presents several problems to boaters. The immediate impact of the formulation is a loss of horsepower and fuel economy. Early indications show drops of 3-5 % in of both categories. The loss of range sounds small, but adds up on boats that are often already stretched to the limit in terms of fuel needs. Additionally, ethanol is a very effective solvent, and has a tendency to dissolve old coatings of varnish and dirt in existing fuel systems. This can lead to plugged fuel filters, and other mechanical problems.
The added amounts of particles associated with ethanol fuel may warrant upgrading filter systems. Many engineers are now recommending that boats using ethanol fuel need to use 10 micron filters. Pre-E-10 systems will likely be using 28 micron filters. Manufacturers such as Yamaha have been quick to respond to ethanol fuel use by introducing replacement 10 micron filters.
The corrosive nature of ethanol can affect fuel lines and other components, causing them to crack and fail. Many older boats will require replacement of all fuel hoses and possibly other system components. Especially affected are boats equipped with fiberglass tanks. Many older vessels must have the fiberglass tanks replaced prior to using E-10 fuels, or face certain engine failures.
Water in E-10 fuel is another problem that boaters must deal with. The introduction of water on E-10 fuel can be disastrous. E-10 can hold up to four teaspoons of water in suspension per gallon. Once this saturation point is exceeded, the solution separates and the gas floats on top while the ethanol and water mix on the bottom. This event is called "phase separation". Ethanol fuel can absorb enough water to reach it's phase separation point in just over 3 months at 70% humidity.
While the phase separation slurry in itself can cause problems by clogging fuel systems, the more immediate problem is that the remaining gasoline has now lost it's original octane value which can cause poor running and in some cases engine damage. When phase separation occurs, the fuel should be drained and replaced.
Fuel storage and winterization has to be handled differently when using E-10 fuels. Manufacturers are warning that fuels need to be stabilized if un-used for as little as 2 weeks. Not all stabilizers are known to be E-10 compatible. Non-alcohol based fuel stabilizer additives are a must for ethanol fuel.