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post #1 of 7 Old 11-17-2006 Thread Starter
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ethanol in gas

I'm not sure if this is the case everywhere, but where I live all gasoline sold contains 10% ethanol. I am wondering what effects this may have with older gasoline engines, and what counter measures if any need to be taken. I have read that the alcohol may attack rubber engine parts such as hoses or o-rings, may disolve old varnish or contaminations from your fuel tank and cause sludge to clog filters, alter the air to fuel ratio causing the engine to run lean, and absorb water causing rough running. I recently bought a "new to me" boat with an older gas engine which is now in storage for the winter, and I will not be able to really try it out until spring. I would like to hear from someone with some real life experience, is it no big deal or is it a nightmare?
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post #2 of 7 Old 11-18-2006
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Ethanol blends of gasoline have a much shorter shelf-life in terms of storage than did the older MTBE formulations. This is due to the ethanol making the gasoline more susceptible to breaking down, especially in a marine environment.

The Ethanol is used as an octane booster, and once ethanol blend gasolines have absorbed enough water from the air, the ethanol will separate out and it will stop working as an octane booster. It also attacks the resin in some of the older built-in fiberglass tanks, and causes huge problems, as the resin residue will gum up the engine and carburetor.

Ethanol also attacks rubber seals, and on older engines, the seals may not be designed to resist this.

One last thing—ethanol blends of gasoline tend to burn hotter, as ethanol is an oxygenator, and this can lead to problems on some engines, as the increased temperatures will cause premature wear and aging.


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post #3 of 7 Old 11-18-2006
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I can second what SD said in relation to seals. Some aviation engine were STC'd for use with auto gas BUT were later recalled due to some rubber seals, fuel lines breaking down due to the ethynol content. Check it out 1st.


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post #4 of 7 Old 11-18-2006
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BoatUS site has several ethanol articles here and since it is winter I post the following here:
October 23, 2006
NEWS From BoatUS
Boat Owners Association of The United States
880 S. Pickett St., Alexandria, VA 22304
BoatUS News Room at

Press Contacts: Scott Croft, 703-461-2864,

What You Need To Know About E-10 Ethanol Fuel

And Winter Boat Layup

This spring and with little prior notice, recreational boaters in most parts of the country were introduced to gasoline containing higher concentrations of ethanol, a corn-based additive that replaced a known carcinogen, MTBE. The new fuel, dubbed “E-10” for its 10% ethanol content, unfortunately has the ability to attract greater amounts of water and “phase separate,” or form two separate solutions in the gas tank, usually over a long period of time. Once this happens, the engine won’t run and internal damage could occur.
With the lengthy winter lay up period upon us, many boaters are asking how they should store their boat over the winter to prevent fuel problems next year. The BoatUS damage prevention newsletter, Seaworthy, tackles the problem in its October issue and has these recommendations:
  • Once phase separation occurs in E-10 gasoline, additives and water separators can’t help. The only remedy is to have the gas and ethanol/water professionally removed from the tank.
  • With any fuel that sits in a tank for a long time, it’s important to add a stabilizer. But understand that stabilizers do not prevent phase separation.
  • E-10 has been a fact of life in certain areas of the Midwest for over a decade and there have been relatively few problems. The best practical recommendation learned from marina operators in the region is to top off a boat’s fuel tanks to about 95% full, leaving room for expansion. A tank that is almost full limits the flow of air into and out of the vent, which reduces the chance of condensation adding water to the fuel. Draining fuel tanks of E-10 gas, while completely eliminating any chances of phase separation, is potentially dangerous and an impractical solution.
  • Whether you believe your boat’s fuel tanks are half full or half empty, leaving a tank partially filled is a bad move. A Midwest marina owner confirmed that phase separation problems typically occurred when boats were stored over the winter with tanks only one quarter to one-half full. In the summer, infrequently used boats with partially filled tanks are also prone to phase separation.
  • Never try to plug up a fuel tank vent to prevent moist air from entering a tank. Without room to expand, the additional pressure could rupture fuel system components.
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post #5 of 7 Old 11-19-2006
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When mixed with non ethanol gasoline it will gel up and plug the fuel filters, don't ask he how i know!
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post #6 of 7 Old 11-20-2006
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Ethanol blend

As far as running lean goes...The stoiocheometric ratio (the ideal ratio of air to fuel, by mass) for gasoline is about 15:1 for perfect burning, and that of ethanol is closer to 13:1. With 10 percent ethanol your mixture will be lean, but IMHO most older engines with relatively primative carburetors tend to run somewhat rich in the first place. Alcohol burns much cooler than gasoline if pure alcohol is used, although when used as an oxygenator in a motor fuel this effect is pretty much negated, but suffice it to say that it will not burn hotter to the point that it will harm exhaust valves or spark plugs. As the others have said your biggest problem will be the hydroscopic tendancies of the ethanol and subsequent phase separation. MTBE, a butyl ether which was used as an oxygenator and an octane booster was used to replace tetraethel lead, but the health risk factors are every bit as unpleasant.(Cancer or heavy metal poisoning? let me see....) Alcohols are not without thier own drawbacks since incomplete burning will produce aldahides, but they stand to be the lesser of the evils at the moment. They may be good for the Midwest farmers as well, and they need all the help they can get.
At any rate there is no choice in the matter so follow the recomended precautions and look after the fuel system and you will be OK.

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post #7 of 7 Old 11-27-2006
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I haven't had any problems running it in a 1975 CorrectCraft with a small block Ford. That's pretty old. I did replace all the fuel lines with new USCG approved fuel line. The old carb didn't care one way or the other.
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