1990 Johnson Evinrude "ES" 9.9 thru 30 Service Manual, P/N 507871, Page 85Get this manual
Carburetor Mixture Adjustment, 9.9-15 The slow speed mixture in this carburetor is controlled by factory adjusted needleThis procedure should only be used if the needle adjustment has been disturbed1The boat 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 temperatureRun the engine in gear at slow speed (700-800 RPM) for three minutes If the adjustment is too lean, the engine will sneeze and backfire, go to Step Ifthe adjustment is too rich, the engine will be rough and unsteady, go to Step 5
111 3If the adjustment is too lean, turn the needle 111 4If the adjustment is too rich, turn the needle