1993 johnson 3hp adjustments

[223mako]

Hi - I have a 1993 johnson 3hp two-stroke. I need to know what the long red screw on the right side (if facing the motor) adjustment settings are. It is no where near the carb and goes under the flywheel. Is this a rich/lean setting or timing advance? I have looked all over the Internet and back for this screw setting. I know you start with threading all the way in until lightly tight but how much do I back it out and what does it do? I do not have the shop manual for this motor

[boats.net]

That would be the idle speed adjustment screw, just to raise or lower idle rpm's.