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Thread: 1978 35hp evinrude mods.(31.8)

  1. #1
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    Default 1978 35hp evinrude mods.(31.8)

    thinking about doing this in 2 stages

    stage 1
    champion plug
    Taylor ignition (spark plug wires) 8mm
    NGK plug boot
    CCMS Reeds
    velocity stack-trying to find somone to building me one currently i think there is someone alreayd on here building them for the 31.8 which is the same setup i know common mod for the 25hp is to use my carb so i assume if they are build for that it would work for mine .
    SS prop


    Stage 2- during next rebuild or refresh .
    port and polish intake and exhaust
    maybe shave the head for a little more compression and or thin head gasket ( copper sheet)
    advance timing
    over size piston when the time comes

    not a race boat but a flat bottom scooter/ skiff out of texas for the bays . looking for punch and a little more get up ! nothing crazy

    any ideas or suggestions let me know

  2. #2
    BoatRacingFacts VIP
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    Get the reeds.
    Check to see if your cdi box has a rev limiter. Get one without.
    Put the rest of your money in a tachometer and gps so you can see what gains or losses you are making.
    Start raising the motor on the transom.
    If the boat gets hard to plane, put an oz plate or drag plate on. Then start raising the motor some more.
    When you see 7000rpm, get a signature propeller with a couple inches more pitch than you have.

  3. #3
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    okay going to order the reeds and the ignition cables forsure mine seem so thin.
    for the tach- i actually scored a super mint plug and play OMC tach for this outboard that plugs into the F&R control box deal works flawless !
    use GPS with my phone and app. BUT may even do the OMC speedo 35-40mph Maybe
    if by OZ plate you mean the OZ hydrofoil plate - i have one installed

    the only thing i have yet to do is buy a micro-Atlas jack plate i know that will make the biggest difference trying to do the smaller less$ stuff first! . and i keep reading how much those velocity stacks do actually work to a extent almost like fine tuning the powerband

    On the CDI what does the one without the REV limiter look like and or whats the part # for it

    EDIT** never mind found the CDI with no limiter for my 1978 35hp > https://www.wholesalemarine.com/john...ower-pack.html

  4. #4
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    so on my engine now i have power pack with part # N-185758 which i think is from ebay . going to order CDI electronics brand to 100% know i get the right one!.

  5. #5
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    The limited power pack has "6100" printed on it. Fat wires are pretty but probably no gain.

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