 |
| Water in ethanol. The water is the dark stuff on the bottom. |
|
Ethanol in Gasoline
With the introduction recently of ethanol-blended fuels marine use, many boaters are concerned about the effect ethanol may have on their marine engines. Ethanol for fuel is highly refined grain alcohol that is mostly produced from corn in the United States but can also be made from sugarcane, wheat, and as the technology advances, municipal waste, straw, paper and wood pulp. Ethanol that is used for fuel has been blended with gasoline and currently in the U.S. is referred to as E-10 which simply means that the fuel is 10% ethanol and 90% gasoline.
The major characteristic of ethanol that is of the most concern to boaters is that it is “hygroscopic” which means that it attracts water and will more readily mix with water than gasoline. Ethanol also has different solvency characteristics than gasoline which will allow it to loosen previously undisturbed matter in fuel systems such as rust and other debris. In addition, ethanol has proven to be harmful to some resins and plastics that were unaffected by gasoline. Loose debris in your fuel can plug filters and affect your engine’s performance. Finally, when mixed with water, ethanol has shown to be corrosive to some metals as it has a higher capability to conduct electricity and therefore galvanic corrosion.
Why is ethanol being used by the marine industry? The issue is the demise of methyl-tertiary-butyl-ether or MTBE. MTBE is an oxygenated hydrocarbon compound that has a high octane rating. Due to EPA regulations requiring oxygenated gasoline to help reduce air pollution in the early 1970’s, MTBE was the compound most commonly used by refineries to supply the additional oxygen. Over time MTBE showed a tendency to work its way into groundwater systems, reservoirs and aquifers, usually as the result of leaks and spills. Obviously contaminating our water supply is bad so the EPA now requires that ethanol be used as a replacement for MTBE.
As far as ethanol’s direct impact on your boat’s engine and fuel system, boaters should be aware of the following issues. Ethanol has a lower (nearly 30%) BTU rating than gasoline which means that the fuel we are now seeing on the Bay will yield a slight reduction in mileage and horsepower. Skippers should check with their boat engine’s manufacturer to determine what impact the use of ethanol could have on their engine’s performance. Ethanol has proven to be damaging to fuel lines, seals, hoses and gaskets that are not ethanol acceptable. At the very least, check these components often for any signs of deterioration and replace damaged parts with ethanol impervious ones. Ethanol can also be harmful to older fiberglass fuel tanks. Resins may be drawn out of the fiberglass and carried to the engine causing serious damage. If your fiberglass tank was manufactured prior to 1990 you should replace it before using ethanol blended fuel.
The final and probably most common problem resulting from ethanol’s use in the marine environment is “phase separation.” If water is present in a fuel tank with gasoline that contains ethanol, the water will be absorbed into the fuel until the saturation point is reached and then phase separation will cause the ethanol and water to separate from the gasoline and settle on the bottom of the tank. If it reaches the fuel inlet it will be pumped into the engine where it can cause significant damage. It is extremely important to check your tank for the presence of water before adding gasoline containing ethanol. If water is present it must be removed. There are no additives that you can put into a tank where phase separation has occurred that will fix the problem. The only solution is to remove the contaminated fuel, clean the tank and then start anew with a fresh load of clean and dry fuel. It is always best to maintain as full of a tank of fuel as possible, this will cut down on the empty space inside your tank thus reducing condensation on the internal walls and baffles of the tank.
When preparing to store the boat for an extended period or winter lay-up it is best to remove all of the fuel from the tank. If that is not possible or practical then maintaining a full tank with a good quality fuel stabilizer is the way to go. Add the stabilizer according to the directions and then allow the engine to run for at least 10 minutes to make sure it has worked its way through the entire fuel system. Shut off the fuel valve and let the engine run until it stops. Make sure to top off the tank and cap any openings to stop the flow of air that can create condensation. Finally, inspect the o-ring on each deck fuel fill and replace if it shows signs of excessive wear, cracks or deterioration.
Good or bad, the use of ethanol in gasoline is here to stay. Boaters just need to be a little more conscientious than in the past regarding your boat’s fuel supply.
|