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  1. #46
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    about 7k

  2. #47
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    Quote Originally Posted by Mark75H View Post
    about 7k
    And what is this monster of 275psi , what exhaust configuration?
    Last edited by FMP; 01-07-2022 at 06:59 PM.

  3. #48
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    Osteen/Deltona, FL
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    Quote Originally Posted by Merc 2.5 View Post
    What kinda fuel or real octane booster , or mix of fuels do I need to run 170lbs compression? This will b a 1st for me and don't wanna burn her up
    Check out Boostane marine. It is not your auto parts store octane gimmick, its the real deal octane additive. I'm a performance calibrator for a living and we use it to take 93 to over 100 on a weekly basis on the dyno.
    83 Vking 150 Mariner 2.5L - re-core in progress

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  5. #49
    Join Date
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    Cardington Ohio
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    Apples to oranges but,

    When we lived in Fla I ran Av gas in all my hi comp motors.

    In the areas popular w/the airboats, you can get it at local gas stations.

    If not, local airports.

    I was running OMCs though that are much larger bore than a 2.4/2.5 Merc so our junk won’t put up w/what your Mercs will.

    At 170 lbs I was mixing 100 oct av w/93 pump w/no problem.
    Lightly loaded.
    As in, drag set up.

    W/no other changes other than adding:
    A passenger
    20 gls fuel
    A 30” lake wheel

    It ran a 1/2 mile before detonating itself to pc’s!

    On the smaller Merc bores, I’m sure it would have been fine.

    Just remember to figure in loading, to your equations ; )

    Remember too, compression on a 2 stroke is way different than a 4 stroke.
    Due to firing twice as often, the combustion chamber builds/retains so much more heat than a 4 that you hit a point of diminishing returns way quicker.

    For drag you see the positives way longer.
    For lake, I think that 170 is as high as I would attempt for an OMC Looper.

    For a Merc you can probably add at least +10 to this.
    I'd rather be competitive w/junk I built in my garage than win w/stuff I bought.


    I refuse to allow common sense to interfere w/my boat buying decisions.


    Checkmate 16' 140 Johnson
    Hydrostream 17' Vector FrankenRude I
    Laser 480 (?) 21' w/GT 200
    Glastron Carlson Conquest w/XP 2.6
    Glastron Carlson CVX 20 w/XP 2.6
    24' Sonic w/twin 250 Johnsons
    24' Sonic w/twin 250 HO Johnsons
    19' STV River Rocket w/FrankenRude II
    Allison XR 2002 w/Frankenrude II
    Hydrostream 18' V-King w/Frankenrude II

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  7. #50
    Join Date
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    Ashland city tn
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    My thinking is I run 145/150 as norm setup but on weekend I just wanna ride , I can pull weight out of it , swap heads to 170lb ,throw some fuel in ,and let her ride. Is it a good idea to do a jet change goin from 93 to mix of 93 and 100 or 110 just less of it. ?

  8. #51
    Join Date
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    No jet change needed unless you were fat just to be fat.

  9. #52
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    Texarkana, Arkansas
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    I have been running 93-91 ethanol free fuel due to supply issues in my area mixed with ACES for years. I do run lighter weight, low pitch props but here is some better details on it.

    https://www.screamandfly.com/showthr...highlight=ACES
    1992 STV River Rocket - bottle fed 260

  10. #53
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    United States
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    Yesterday I ran my warmed up 2.5 225 hp mariner with 164 pounds of compression on 93 octane pump gas and 1 ounce of aces per 6 gallons of fuel. No problems whatsoever with this concoction.

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