1981 115hp "evinson"(1/2 johnson 1/2 evinrude) bad idle miss

Discussion in 'Outboards' started by captwanabee, Jul 4, 2011.

  1. captwanabee
    Joined: Jul 2011
    Posts: 9
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    Location: calif.

    captwanabee Junior Member

    i have 110 psi compression on all 4 cyl. new plug and plug wires, new power pack ,no dva adapter for further trouble shooting,starts normal sounds great at high rpm starts a "coughing" miss at idle and stops,any ideas?:?:
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    It could be the reed valves.
  3. powerabout
    Joined: Nov 2007
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    Location: Melbourne/Singapore/Italy

    powerabout Senior Member

    as gonzo says or too lean or both
    its a 3 circuit carb so idle air bleeds are looking at you just inside the top of each venturi when you pull the front cover off.
    A broken reed will make a miss every stroke (usually) and a lean cylinder will propably do it with a gap of a few seconds..maybe
    Badly synced carbs will also do this as will badly fitting throttle butterflys in the carb when the throttle is closed ( as it should be at idle)
    Float level too low will also do this
    quick test of lean jetted at idle is to just place a pencil into the idle air bleed and that will richen each cylinder, see if problem goes away
    It was common in those days to alter the std idle air bleeds to get the engines to purr like a kitten

    PS also make sure it is warm enough

  4. judgegage
    Joined: Jun 2011
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    Location: Fl

    judgegage Junior Member

    Is it half n half block?
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