miss fire?

Discussion in 'Outboard Maintenance' started by spr2500@aol.com, Jun 20, 2011.

  1. spr2500@aol.com

    spr2500@aol.com I Love microskiff.com!

    Finaly got to run the boat for the first time, and every thing went somewhat smoothly.. The only thing is, twice (@ different speeds/rpms) it seemed that the engine would miss fired or actually shut down for 1 revelution then would continue to keep running fine..
    the enginge is a 1991 Jouhnson 25hp..
    This all took place over about 2 hours of continues running with most of the time at idle, but one of the times it happened I was at about 3/4 throttle and the other time just above idle going into the launch.
    seemed to be a bit of oil dripping from the exhaust when I got in and the back of the mount stained pretty good from the exhuast it self (white engine)
    To gas/oil ratio to high? 50:1 mix, but I may have over done the oil a bit ::) or vice versa?
    Could it be air in the lines causing a interuption of fuel to the cyclinders?
    Just chalk it up to a 20 year old engine?
    Thanks in advance for any help!
  2. Brett

    Brett > PRO STAFF <

    Possibility that the original ignition electronics are still on the block.
    They do get old and wear out. Intermittent short caused by cracked plug wire,
    cracked coil or sensor, bad plug, dirt in the carb can all contribute to misfiring.
    Odds are it's time for a complete tune-up.

  3. noeettica

    noeettica Well-Known Member

    Run the motor on the hose in the dark look for arcing around the ignition components ...

  4. spr2500@aol.com

    spr2500@aol.com I Love microskiff.com!

    Brett, yeah an tune up is defently in order..
    NoeEttica, thanks for the tip, I'll take a look tonight.
    THanks guys! Very much apreciated!!