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Thread: What octane fuel is required

  1. #1
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    What octane fuel is required

    Hey guys yes its ME again with yet again another question, sorry! I am trying to work out a satisfactory fuel solution for at my lake house which is in MN and the only place on my lake that sells fuel is the 10% Ethanol which in the end comes out to like 85 octane, I know that is to low for my boat and I really dont want to run any Ethanol at all, its pretty much an all around pain.
    My boat is running a 9 to 1 compression ration with good heads and a full roller cam etc, the trickier part is the engine is supercharged but only pushing 4 pounds of boost, the engine is carburated and has no detonation sensors of any kind except my ears. The normal usage for the boat will be in the 3500 to 4000 RPM range with an occasional bursts to 6000 RPM and they would be short in duration. With this information can I get by on 91 octane no Ethanol fuel? I know the easy answer is to buy 107 and cut it 50/50 with 91 octane which would give me a final rating of around 107, I am trying to avoid that if possible?
    Thoughts anyone?

    Karl

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    fuel

    Sorry guys my mistake I would buy 114 octane race fuel and cut it 50/50 with 91 octane for a net 107 octane for the boat.
    Thanks
    Karl

  3. #3
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    Karl, you do not need to run 107. That would be way more octane than needed.

    I believe you said you have aluminum heads, which will make the motor less likely to detonate vs iron heads. Even with iron heads, I wouldn't hesitate to run 94 if you can get it. The Chevron's here (Canada) sell 94.
    IMO, 91 is kind of iffy. I've run 91 before without issue, but I'm always easier on the throttle with 91.

    It may be ok, but maybe not.....and it's really hard to tell just by running the boat because detonation is tough to hear in a boat because of all the wind noise.
    Why is faster never fast enough.

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    fuel

    Yeller thanks for your thoughts, I would sure agree with you that 94 or even 93 octane would be enough, I have a car that I run 91 (no ethanol) with an 104 plus octane booster any thoughts on using an octane booster, then I could buy 91 octane (no ethanol) add a booster and would that be a reliable way to get to 94 Octane? and if so do you have any product suggestions?

    Thanks again Yeller your knowledge is very much appreciated!
    Karl





    Quote Originally Posted by yeller View Post
    Karl, you do not need to run 107. That would be way more octane than needed.

    I believe you said you have aluminum heads, which will make the motor less likely to detonate vs iron heads. Even with iron heads, I wouldn't hesitate to run 94 if you can get it. The Chevron's here (Canada) sell 94.
    IMO, 91 is kind of iffy. I've run 91 before without issue, but I'm always easier on the throttle with 91.

    It may be ok, but maybe not.....and it's really hard to tell just by running the boat because detonation is tough to hear in a boat because of all the wind noise.

  5. #5
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    Did you ever think about AV fuel?............100LL for lean 130LL for rich
    1983 Cigarette 35' Mistress
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    NEVER FORGET 9/11

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    Quote Originally Posted by Karl Kostman View Post
    Thanks again Yeller your knowledge is very much appreciated!
    Karl
    That could be dangerous, if you think I'm knowledgeable. You realize you're taking advice from someone that's been working on their motor for over 7yrs and still haven't finished yet.

    Can't really help you on the octane boost question. I've never used it, but everything I've ever heard is that it's junk and doesn't do anything. That's internet talk though. I've never seen test results for or against.
    Why is faster never fast enough.

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    My son-in-law's family is into high performance cars/boats, and they have used Boostane with good success. https://boostane.com/?_vsrefdom=adwo...MaAv9QEALw_wcB

    The only adverse effect is that they seem to go through spark plugs more quickly.
    “Oh right, because you walked into strippers discount warehouse and said ‘Help me showcase my intellect.’” - Archer

    Bill
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    octane levels

    Thanks much guys and the Av 100 LL is good fuel and I burned a lot of it in my Mooney days but there again I have to haul all my fuel in and to make it worse I have to go to the airport to get it. I am going to look at an additive, granted I am leery of such items or I will fill the boat with 91 octane NO ethanol and add ten gallons of 114 octane race gas, that should get me into the 95 area that I am looking for.
    Thanks you guys very much for your ideas and suggestion on this matter, I now just need to get rid of a whole lot of ice!!
    Karl


    Quote Originally Posted by Just Say N20 View Post
    My son-in-law's family is into high performance cars/boats, and they have used Boostane with good success. https://boostane.com/?_vsrefdom=adwo...MaAv9QEALw_wcB

    The only adverse effect is that they seem to go through spark plugs more quickly.

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