1990 Johnson Evinrude "ES" 40 thru 55, P/N 507872, Page 49Get this manual
Engine Idle Speed Adjustment 1The boat and engine must be in the water under normal operating conditions with the correct propeller installed The boat's movement must be unrestrainedThe boat must not be tied dock or trailer2 Start the engine and allow it to reach normal operating temperature Check idle RPM in FORWARD gear with an accurate tachometer 1171 i'"l 4StopAdjustengine to speed screw to obtain rotating the prevent contact with partsthe idle recommended RPM Turn screw counterclockwise to lower idle speed Turn screw clockwise to raise idle speed