My 1989 70 Evinrude idles very rough up to approx 2000 RPM beyond that works perfectly. Done a compression test all at 120 changed plugs and leads. Any ideas?
Might need a good carburator cleaning, or at least a heavy dose of SeaFoam in a few gallons of gas and run it hard for awhile (wide open) to decarbonize the motor inside. Try re-adjusting the slow idle screw on it? This is the fuel/air ratio setting for your slow speed (idle). You can remove the screw and shoot some carb cleaner into the hole, and then put the screw back in where it started from.
To know where it started at, you will turn the screw all the way in until it is seated ( DO NOT over tighten this screw all the way in) just lightly seated, counting how many turns you turned it in before you totally remove the screw, so you know how many turns to reset it at (from where you started). I use SeaFoam religiously and it really helps things to stay clean.
