1984-1986 Mercury Force 4HP Outboards Service Manual, Page 16Get this manual
4Slowly turn id le needle coun terclockwise until motor speed decreases and operation becomes rough due to overrich mixture(Note ad justment position
'5Slowly turn idle needle clockwise: motor operation
will become smooth and speed will increaseContinue turn ing adjustment clockw ise unti motor speed slows or misfires from too lean mixture
6Turn idle screw to mid point between settings noted steps and 5Figure 6
NO RIN GS OR GROOVES ALLOWED THIS LENGTH