How to run E-85 biofuel in my outboard?

Discussion in 'Outboards' started by codyjsmith, Mar 6, 2007.


Have you ever herd of E-85 biofuel.

  1. Yes

    31 vote(s)
  2. No

    8 vote(s)
  1. codyjsmith
    Joined: Mar 2007
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    Location: south carolina

    codyjsmith New Member

    Hi im looking for someone who can tell me what changes I need to make to be able to run the new E-85 biofuel in my outboard motor. I have an 1982 115hp johnson with 1 3/16" carbs, the stock jets are 54, 37, 34. I know, or if I have to enlarge the jets (orficeses), how much biger do I need to go and which ones do I need to enlarge. I have been around the block with this question and no one has yet to answer it for me. Hafe of the machanics didn't even know what E-85 fuel was so let me explain it for those who still do not know, it is 85% ethonal and 15% gas. Simulor to what they use to call gasohal. And yes you can buy it at your local gas pump. It is 105 octane and is cheaper than regular. If any one can answer this I think you so much.

  2. charmc
    Joined: Jan 2007
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    charmc Senior Member

    While 10% ethanol, E10, is OK in modern outboards, generally those built in the last 10 years, E85 is currently not recommended at all. Apart from carb changes, you'd need to change most seals and all non-metallic fuel lines/hoses. Ethanol is a solvent with properties different from those of gasoline. It will destroy most of your existing rubber & plastic seals, hoses, etc, and it will dissolve crud in your existing tank, lines, etc, transferring it to the inside of the engine. If your boat has a fiberglass fuel tank, forget any ethanol blend at all, it will dissolve the resin and leak fuel into your bilge. Another consideration is water in the fuel tank. Water is absorbed easily by E85, leading to corrosion/rust and performance problems, and possible engine damage. Overall, I'd stay away from it until someone with genuine expertise publishes guidlines for conversion. Besides, the reason you need to rejet is because E85 has much lower energy content, so you'll use 20-30% more fuel. Not really accomplishing much, IMHO.

    Here are some links with more details:
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  3. charmc
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    charmc Senior Member

    There's a reason why marine mechanics don't know about E85

    The reason marine mechanics haven't heard of E85 is because it's not approved by any boat industry association or standard-setting body for recreational boating use, for all the reasons listed in my earlier post.
  4. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    Your 1982 motor is probably not a good candidate for high-grade ethanol. As charmc says, most of your motor's soft bits are probably not of high enough quality to handle this fuel. Many common biofuels (ethanol, most biodiesels) are good solvents and much cleaner than conventional fuel, and will do a nice job transporting all the crud in your fuel system to the fuel filter element. There are no internal modifications but the fuel injectors or carbs do need to be calibrated appropriately.
    Cars that can run on E85 have soft parts (hoses, gaskets etc) made of higher quality materials, and computer controls to allow the engine to switch seamlessly between different fuel blends. I have never seen or heard of consumption going up 30%, but a 15% increase (by volume) is not uncommon.
    In short, 10% should be fine and up to 20% might work, but don't go any higher unless the engine manufacturer recommends the higher grades.
  5. Frosty

    Frosty Previous Member

    If you can get a gallon, put it in and try it. You may have slow running problems and this would be a problem for the gear selection --but try it, let us know.
  6. stonebreaker
    Joined: May 2006
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    stonebreaker Senior Member

    It will cost you about 10%, power-wise. In an engine optimized for alcohol, you can make quite a bit more power because the high octane allows you to run 13:1 compression or even higher, but because of ethanol's lower energy content, as mentioned above, it will cost you both power and mileage over straight gas in a converted gasoline engine.

    Gasoline burns at 14:1 air/fuel ratio, and methanol burns at 9:1. I don't know what ratio ethanol burns off the top of my head, but I'd guess it's somewhere in between - maybe 11 or 12 to 1.
  7. RAWRF
    Joined: Dec 2006
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    Location: Eagle, Alaska

    RAWRF Junior Member

    You would be surprised at what those old Johnsons will run on without any damage, short or long term. I have an old 1985 Sea Horse and one time I ran out of gas while going up the river because a bear climbed into the boat and tore open a couple cans, so I stopped at this old cabin and drained the gas out of a 3 wheeler with 3 flat tires that probably hadn't been running in 5 years or more, and in an old shed with the roof caving in I found an unopened can of methanol and a quart of motor oil. I used this as my premix. The whole mixture was the color and consistency of milk. The engine sputtered a bit and wasn't as powerful but got me where I was going, and I didn't bother making any kind of carb adjustments whatsoever. I still have that engine and have never done anything to it besides regular maintenance.
  8. charmc
    Joined: Jan 2007
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    charmc Senior Member


    Great work making emergency fuel, and I'm glad to hear the bear got your fuel and not you! 'Course, the smell probably drove him/her away.

    I'm guessing that what you made was probably a 5, 10, or maybe 15% methanol blend with gasoline, similar to the EPA-mandated methanol blends replacing MTBE blends in high population density regions, and similar to E10 ethanol blend approved for most of today's outboards, and you used it once.

    E85, 85% ethanol, to be used on a regular basis, is a whole different animal. Don't misunderstand my first post; I'm not against it, just against the stupid media hype that misinforms too many people, making them think it's just a question of getting a supply of the fuel. Phased in with proper precautions and preparation, E85 can be one option, out of several, for reducing reliance on imported oil, which seems far too often to be under the control of unstable or nasty governments.
  9. gonzo
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    gonzo Senior Member

    Many years ago when I was working in Brazil, I got a lot of experience with gasohol and straigh ethanol. It destroys all rubber parts (diafragms, hoses, etc.) and also corrodes the carburator bowls. They changed the rubber compounds to neoprene or something like that and carburators are either cast iron or plated inside. The HP is lower unless it is turbo or super charged in which case the pressure can be higher. Cold starts are a bit more difficult too.
  10. mrmoto58
    Joined: Mar 2007
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    Location: winnipeg manitoba canada

    mrmoto58 Junior Member

    Hi I also had a run in with gasohol my fishing partner used my boat and it had a 98 .75 merc on it and he used gasohol in it not noing .he had to bay to get the carbs cleaned and re tuned .Ted
  11. redtech
    Joined: Feb 2007
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    Location: suger pine, ca

    redtech Senior Member

    listen just about everyones right don't use it on the outboards or boats all together yet. to add to the argument ethanal also absorbs water (just something else we need in the fuel tank) and reduces the lubricating value of you fuel oil mix. engine manufactors say only 10% max ethanol theres a reson way and lets not forget about fungus that can grow when left to long in the tank
    does anyone remember soy diesel when it first came out for sailboats???
    just saying give it time don't jump one the wagon yet it may not float.
  12. openboater
    Joined: Mar 2007
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    Location: central NYS

    openboater Junior Member had a geat write up last month by their resident expert 'Max' on using ethanol in old engines. He used some pretty hi concentrates as I recall with no detrement to the engines.
  13. redtech
    Joined: Feb 2007
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    Location: suger pine, ca

    redtech Senior Member

    openboater thank you for the article this is the first modern test i've seen just been going off of history e-85 was gasahol from the 50's and 60's
    lets just keep in mind sythetic oils, modern rubbers, hot sparks, and good compression all these things were not around when e-85 first come out and went bust.
    willing to try something new but playing safe for now
    technology may have fixed this one
  14. ted655
    Joined: May 2003
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    ted655 Senior Member

    I just read the Tohatsu manual. If any type of alcohol mix fuel is used, the warrenty is void. Good enough for me, I get the point.

  15. dragonjbynight
    Joined: Apr 2008
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    dragonjbynight Senior Member

    Depending on composition and source, E85 has an octane rating of 100 - 105[4] compared to regular gasoline's typical rating of 87 - 93. This allows it to be used in higher compression engines which tend to produce more power per unit of displacement than their gasoline counterparts. Since the reciprocating mass of the engine increases in proportion to the displacement of the engine E-85 has a higher potential efficiency for an engine of equal power. One complication is that use of gasoline in an engine with a high enough compression ratio to use E-85 efficiently would likely result in catastrophic failure due to engine detonation, as the octane rating of gasoline is not high enough to withstand the greater compression ratios in use in an engine specifically designed to run on E-85. Use of E-85 in an engine designed specifically for gasoline would result in a loss of the potential efficiency that it is possible to gain with this fuel. Using E-85 in a gasoline engine has the drawback of achieving lower fuel economy as more fuel is needed per unit air (stoichiometric fuel ratio) to run the engine in comparison with gasoline. E-85, 85% Ethanol by volume, also has a lower heating value (units of energy per unit mass) than gasoline leading to a reduction in power output in a gasoline engine. E85 consumes more fuel in flex fuel type vehicles because of its lower stoichiometric fuel ratio and lower heating value. So in order to save money at the pump with a flex fuel vehicle the price of E85 must be much lower than gasoline. Currently E85 is about 5-10% less expensive in most areas.[5] More than 20 fueling stations across the Midwest are selling E85 25%-40% cheaper than gasoline.[6] E85 also gets less MPG, at least in flex fuel vehicles. In one test, a Chevy Tahoe flex-fuel vehicle averaged 18 MPG for gasoline, and 13 MPG for E85, or 28% fewer MPG than gasoline. In that test, the cost of gas averaged $3.42, while the cost for E85 averaged $3.09, or 90% the cost of gasoline.[7]

    Wikipedia definition as the question had also crossed my mind, however I would follow the previous reccomendations against using it. The extra savings would be eaten up by the greater consumption. Most study's done on E85, mention it is not reccomended for any motor not specifically designed for it.
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