1998 Johnson Evinrude "EC" 9.9 thru 30 HP 2-Cylinder Outboards Service Manual, Page 62Get this manual
Description of Fuel System
ITJ1The fuel pump is of the diaphragm-displacement type and is operated by changes in crankcase pressureAlternately, suction and pressure in the crankcase are transmitted to the pump diaphragm2The carburetor meters and distributes the fuel consumedIt controls engine speed and power output by varying the intake charge densityTo react correctly to wide range of operating conditions, the carburetor has multiple fuel mixing circuits