1998 Johnson Evinrude "EC" 9.9 thru 30 HP 2-Cylinder Outboards Service Manual, Page 87Get this manual
Carburetor Mixture Adjustment20 1Start the engine and run it in FORWARD at one-half throttleAllow the engine to reach normal operating temperature
2Tiller ModelsAs you face the steering handle, turn the idle speed adjustment knob counterclockwise to full SLOW speed position