Today's Marine Fuel Choices
New Options Challenge Boat Engine Operation and Maintenance
New fuels are being introduced into the marine marketplace that are changing the way boaters operate their vessels. Increased operator knowledge can ease the transition.
Boaters are seeing many changes in the marine fuels available for their use. Governmental regulation has slowly changed the composition of boat fuel to better help reduce harmful emissions. Boat operators need to be aware of the possible problems these fuels can pose to their craft. Currently there are three new fuel formulations showing up in the marketplace; they are ethanol blended gasoline, low and ultra-low sulfur diesel, and biodiesel. An understanding of these fuels will help boaters purchase the correct fuel, equip their boats properly, choose the right filters and improve marine propulsion performance.
Ethanol-blended gasoline - Ethanol is a blend of gasoline and ethyl alcohol. Ethyl alcohol is an excellent solvent and is hydroscopic, that is it adsorbs water. As a solvent, ethanol will dissolve sealants used in fuel tanks. It has a cleaning effect on tanks and fuel system components that can release fine metallic particles and dissolved sealants into the fuel delivery system. This contamination can plug fuel injectors, filters and carburetors. The greatest problem associated with ethanol fuel is the adsorption of water out of the atmosphere. Fuel stored onboard a boat can degrade in less than a month with a combination of water and ethyl alcohol separating from the gasoline. This is known as phase separation and it can harm marine power plants, produce excessive engine deposits, decrease fuel economy and reduce power generated by an engine.
There are many things boaters can do to prevent problems with use of ethanol-blended gasoline in their vessels. Once it is apparent phase separation has occurred, the only good course of action is to pump out the fuel tank, clean it and replace to the fuel with fresh product. Inspect the condition of onboard fuel and fuel tanks regularly. Control the water that can enter the fuel system. Check the condition of fuel lines, filler hoses and gas caps. Use a quality water separating fuel filter and change the filter element often.
Low and ultra-low sulfur diesel - The Environmental Protection (EPA) is requiring the use of low sulfur diesel by boaters and the marinas that distribute diesel fuel. Two forms of the new low sulfur diesel are available to marinas. They are low sulfur diesel (LSD) that does not exceed 500 parts per million (ppm) of sulfur and ultra-low sulfur diesel (ULSD) that can not exceed 15 ppm of sulfur. Marine fuel previously available at most marinas can run up to 5,000 ppm of sulfur.
Sulfur in diesel fuel acts as a lubricant that extends the life of seals and fuel injectors. Use of these new forms of diesel fuel can reduce protection provided to the engine and reduce performance. Low sulfur diesel is less stable, contains more moisture, is more prone to bacterial growth and causes fuel filters to plug up sooner. Diesel engines designed to ASTM standard D975 can safely use ULSD fuel. Diesel engine operators should consult with their mechanic and engine manufacturer on strategies to better cope with the new fuel. New seals, injectors or other components may be required for good longterm performance.
Biodiesel - This is a class of fuel that is derived from vegetable oils and animal fats. It is relatively clean burning, represents itself well as a renewable resource and is more environmentally friendly than use of diesel fuel. Government research, subsidies and emission regulations are driving the increased use of biodiesel.
Biodiesel displays good lubrication properties, but suffers many of the problems associated with use of low sulfur diesel. It has low storage stability, is prone to supporting bacterial growth and provides less energy for combustion. Standards are not uniform for biodiesel production and quality varies between producers. Most marine manufacturers will only approve the use diesel blend of fuel that contains less than five percent biodiesel. Conversion of the engine is required to use unblended biodiesel fuel. Major diesel engine manufacturers like Detroit Diesel, Cummins and Navistar have tested biodiesel blends of up to thirty percent that have not degraded fuel system performance.
