The Boat Doctor provides valuable information about use of ethanol in boats

This perennial Black Bay hotspot is producing big trout and reds.

I look forward each month to receiving my issue of Soundings Trade Only Magazine. This magazine is full of information and news for and about the marine industry. In this month’s issue was an article about ethanol and some of the concerns expressed by experts in the marine industry regarding a petition to the Environmental Protection Agency to increase the ethanol blend in gasoline from 10 percent to 15 percent. This petition has been submitted by a lobbying group that represents ethanol producers.

It was approximately 30 years ago that the EPA first mandated a 10-percent limit on ethanol when mixed with gasoline. Ethanol cost more to produce than gasoline — so much more that the federal government actually subsidizes the producers over 50 cents per gallon via a tax credit, and engines actually get less gas mileage on E10 than they would on good ol’ gasoline.

Ethanol for fuel is highly refined beverage (grain) alcohol, approximately 200 proof. It can be produced from natural products such as corn, sugarcane and wheat. Ethanol used for fuel has been ‘denatured,’ or rendered unsafe to drink, by the addition of a hydrocarbon (usually gasoline).

When the EPA first directed the production of oxygenated gasoline to help reduce smog, the additive of choice at that time was MTBE (methyl tertiary-butyl either). Today most states have outlawed the use of MTBE because it has a nasty habit of working its way through the earth and into the ground water system.

Now ethanol is being used as a substitute to oxygenate gasoline and help reduce smog emissions of internal combustion engines. Ethanol can help us achieve a cleaner environment and may reduce some of our dependence on foreign oil, but we should be aware of the dangers of this product and the effects it may have on our outboard motors.

Ethanol is a water magnet. It will pull water out of the air right through your gas tank vent hose. In our high-humidity climate, this can be especially harmful to your engine. As moisture is absorbed, the molecules of alcohol/water become heavier than the gasoline in the tank, and they settle to the bottom. This process is called “phase separation.”

As more water is absorbed, it will eventually separate all of the ethanol from the gasoline and settle to the bottom of the tank. This will leave you with a lower octane fuel in the tank, and if the separated mixture becomes great enough to reach the fuel pickup tube, it will be sucked up into the engine, where it can clog filters, carburetor jets and fuel injectors. It may even cause your engine to run lean and burn one or more pistons.

Another nasty habit that alcohol has is to act as an extremely efficient solvent. If there is any gum or varnish build up in your tank, the alcohol will dissolve these deposits, and they will be sucked into the engine fuel system. If that weren’t bad enough, the alcohol and water combination mentioned above may also encourage the growth of bacteria in the fuel tank, which turns into sludge and further damages the fuel system.

If your boat is equipped with a fiberglass fuel tank that was manufactured prior to 1992, you may find that the alcohol is causing your fuel tank to decompose. The alcohol actually dissolves the resin that binds the fiberglass fibers of the tank. When this happens, the only solution is a very costly removal and replacement of the tank.

Current law mandates a mixture of no more than 10-percent alcohol. Any mixture that exceeds the 10-percent maximum mandated by law can cause substantial damage to your outboard motor. Fuels containing a higher level of ethanol are not considered acceptable for use in most modern outboard motors. The use of these fuels can void your engine warranty.

In Louisiana, we are fortunate that we have ethanol gas pump labeling laws. By state law, if a dealer has ethanol added to the gasoline, he must post an E10 sticker on the pump.

If you have any doubts about the fuel that you are purchasing, you may want to invest in an ethanol fuel test kit. I found these kits through a Google search for “ethanol alcohol fuel test kit.” The one that I found cost approximately $25 plus shipping and handling.

You can simply test the fuel content at the pump before purchasing. It is a quick, two-step process, and it will give you results from 0- to 30-percent alcohol. I have seen reports of alcohol levels in excess of 40 percent in another state. This test kit could save you a lot of headaches.

So what can you do to minimize the possibility of having engine problems related to ethanol? On almost every web site I visited, the No. 1 recommendation was to avoid using ethanol fuel if possible. Second on the list would be the installation of a 10-micron water-separating fuel filter system in your boat.

If you have ethanol fuel in your gas tank, do not allow it to set up for more than 90 days. Remember ethanol pulls water from the air, which degrades the octane of the gasoline in your tank. The shelf life of ethanol is much shorter than 100-percent gasoline.

Be extremely careful in using any fuel additives. Read the label carefully. If it contains alcohol in any form or quantity, do not add it to your gas tank. You will be increasing the alcohol percentage in the gasoline and risking damage to your engine. Fuel stabilizer is a must, but only those brands that do not have alcohol components.

One last caution: There is no such thing as a miracle product. Once you have phase separation in your fuel tank, the only way to cure the problem is to drain the tank, clean it and dry it. The fuel lines will have to be purged and the carburetors or injectors cleaned.

I won’t make a recommendation on whether to keep your gas tank full. I have seen opinions on both sides of the issue. Using your boat more often may be a better solution — if the wife will let you get away with it.

If you have any questions about your boat, motor or trailer you can contact me at