Recent content by 77jeff87

  1. 7

    what is causing timing mark jitter at part throttle?

    My '91 Merc 25 hp has a jittery timing mark. At idle, it as at about 0?, and mostly steady except for a few pops or stumbles (motor jerks side to side slightly), but when I increase the rpm's slightly, it pops, backfires ocaissonily, and the mark jitters in the advance and retard directions. I...
  2. 7

    '90 Merc 25HP fix for rough low speed?

    My '90 Merc 25HP runs rough at low speed and I am asking if someone can help identify the cause. At about 1/8 to 1/4 throttle, the motor runs at a low rpm for a few moments, then abruptly increases in rpm without more throttle. Starts fine and runs well at WOT. I checked the spark plugs and...
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