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Why is ethanol a problem for marine motors?

Last updated 6 years ago

Boat Tree Marina located in Central Florida offers non ethanol fuel for its boaters. Boat Tree Marina is a full service marina located in the metro Orlando area offering wet boat slips, dry boat storage, covered boat storage, boat sales, boat consignments and full marine service. Other amenities included are Free pump outs, Crawdaddy's riverside restaurant and pool side bar, locked gates, boat rentals, non ethanol fuel, 25 ton travel lift & 100% floating docks. 

Why is ethanol a problem for marine motors? Two reasons.

First, alcohol is a great solvent. It can dissolve many materials used in engine construction before ethanol mandates (1995), including hose materials. It also removes the petroleum "varnish" that always builds up in engines.

Deteriorating hose lines can lead to dangerous fuel leaks. And the solids from hoses and varnish can be rendered in such fine particles they pass through fuel filters and clog other engine parts, including fuel injectors.

Second, alcohol is hygroscopic -- which means it absorbs water.

If left in a tank long enough, the ethanol in a humid environment will separate, creating a sludge on the bottom of the tank where it will flow into the fuel line pickup, causing more problems.

This isn't a big concern for cars for two reasons. First, drivers typically use a fill-up in a matter of days. Second, there is no way for outside moisture to enter a car's fuel tank.

Boat owners are not so lucky. The typical boater will leave fuel in a tank for weeks or even months. And because boat fuel tanks must be vented, the humid Florida atmosphere has an always-open avenue to the water-absorbing ethanol.

Is this always a problem for boaters? It doesn't have to be, and it shouldn't be.

Marine manufacturers consider E-10, which is supposed to have no more than 10 percent ethanol, safe for use in motors fewer than 10 years old. Federal figures show 70 percent of the gas pumped today is marked as E-10, and many states, including Florida, require retailers to mark the ethanol blend on each pump.

Unfortunately, retailers often don't follow that mandate, and the gas they carry may contain a higher level of ethanol than the refinery reported. Independent studies have shown some fuels marked E-10 containing as much as 40 percent alcohol. And in an effort to meet federal guidelines, car makers are producing more flex fuel vehicles (FFV), which are engineered to use E-85 fuels -- 85 percent ethanol, 15 percent unleaded gasoline.

What can boaters do? Be proactive.

First would be to always use non ethanol fuel in your boat. 

If the option is not available to use non ethanol fuel in your boat check to make sure the station where you purchase your fuel is listing the ethanol blend on its pumps. If it is more than E-10, search for another retailer, and tell that retailer why he is losing, or gaining, your business. Share that location with other boaters.

Don't stop there. The retailer may be

unwittingly selling fuel that has more than 10-percent ethanol, but you can check his product by purchasing a fuel tester. These devices are available from a number of online sites for as little as $25, and they are reusable.

Boat Tree marine mechanics say it is a wise investment. They would use the device with every fuel stop.

"Motors made recently won't have any problems with E-10, but the problem is a lot of times you're shopping blind -- you're just not sure what you're getting. Reports have been made on cases in which the modern, high-horsepower outboards that use fuel injectors have experienced blown blocks.

"If you're using fuel with a high enough alcohol content, it will break that varnish down into such fine particles that it can get through the fuel filters, then clog the injectors, and that cylinder to run lean."

That will cause overheating, which can result in the engine throwing a rod or simply seizing. The news can be even worse.

"The motor can be under warranty, but if the problem is found to be caused by using fuel higher than E-10, the manufacturer might not cover the damage.

Even then, there is no guarantee problems won't develop in our humid local environment. Since E-10 has less alcohol than other blends, it wil

l absorb less water, but the potential is still there.

With that in mind, there are two steps that can help reduce the chances of a problem.

First, try to find a station that sells alcohol-free fuel. There reportedly are some in the metro area, but also be sure to use your fuel-tester to make sure.

Second, try to plan your fuel usage so you never store the boat with much left in the tank. This is especially important if you're one of those boaters who won't be boating much during the winter.

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