1988 Johnson/Evinrude "CC" 40 thru 55 Models Service Manual, Page 64Get this manual
Engine Idle Speed Adjustment 1The boat and engine must be in the water under normal operating conditions with the correct propeller installedThe boat's movement must be unrestrainedThe boat must not be tied to dock or trailer2Start the engine and allow it to reach normal operating temperature3Check idle RPM in FORWARD gear with an accurate tachometer 1171 ill 4StopAdjustengine to speed screw to obtain rotating 1the prevent contact with partsthe idle recommended RPM Turn screw counterclockwise to lower idle speed Turn screw clockwise to raise idle speed&