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Ethanol: More woes for boaters

November 22, 2008
Capt. George Tunison,
Now that the cold weather season is upon us, some of us will not be using our boats as much and that may mean big trouble the next time you try to start old faithful for a day on the water.

Unless you burn full tanks of fuel and refill them regularly the words “phase separation” will become part of your vocabulary. The additive ethanol, or E-10, that has been forced into our fuel tanks has become a nightmare for the boating industry.

E-10 gasoline contains up to 10 percent of the additive, which is the maximum amount recommended to run in Yamaha outboard motors.

The two issues affecting boaters the most:

n E-10 attracts moisture: The water in your fuel tank bonding with the ethanol is the issue. Ethanol is a full two points of your octane rating. When moisture enters the fuel tank, the ethanol bonds with it and sinks to the bottom of the tank (leaving the gas), thus lowering the fuel’s overall octane rating and creating a gel-like mess in the bottom of the tank.

This process is called phase separation. (89 octane gas thus becomes 87 octane.)

Lowered octane rating means poor performance. Since boat fuel tanks naturally aspirate moist air through the tank’s vent during heating, cooling, and operational cycles, plus the water that occurs in gas station storage tanks, you are bound to have some amount of water in your system.

n E-10 is a solvent: A super solvent in fact. It will dissolve fiberglass fuel tanks, rubber hoses, certain plastics and fuel lines, fuel system sealants and gaskets. E-10 will clean rust from steel and iron parts, oxidization from aluminum, and varnish and gum from fuel tanks and lines.

This mess all ends up in your tank, which your fuel pump tries to send directly into the motor, clogging up everything. Bad news for that planned fishing trip.

Older boats with years of sludge, varnish and gum buildup are the first targets of E-10. Also, boats that sit for any length of time in storage or on a lift behind your castle with a half-full tank are prime candidates for problems.

All boats, new and old, are vulnerable.

I had a conversation this week with Scott Rush, owner of San Carlos Marine in Fort Myers. He said ethanol now is responsible for a full 50 percent of all service calls at his facility and has become a huge problem for his customers and the industry in general.

I asked about the new additives that are appearing on the market to address this problem and he said his company is doing ongoing testing of the more popular brands in an effort to help customers, but has not found any that he would fully endorse at this point. He warns to be wary of any additive that touts itself as a cure-all for ethanol and water woes since to his knowledge they don’t exist yet.

He also tells me that Yamaha advises changing fuel filters often and the use of water separating filters is mandatory. Yamaha recommends using their 10 micron fuel filter (Mini-10) in your fuel system as well as trying to keep your tanks as full as possible.

Neglected or old fuel will be a huge problem in your motor. Older boats with years of deposits and varnish buildup will go through a period of problems till all the ethanol dissolved contaminants are eliminated by regular filtering of the fuel source.

I like using the Racor water separating filter which allows you to actually see some of the mess that is being fed into your engine. Inspect often, change regularly. Also, inspect the smaller filters under the cowl.

Filters aren’t cheap, but the alternative is a hundred times more expensive.

Capt. George Tunison is a Cape Coral resident fishing guide. Contact him at, or Flying Fins Sportfishing.

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