1998 Johnson Evinrude "EC" 40 thru 55 2-Cylinder Service Manual, P/N 520206, Page 66Get this manual
Description of Outboard Fuel System
The VRO pump assembly is combination mechanical fuel and oil pumps and fueloil mixer powered by crankcase pressure and vacuum pulsesThe VRO pump injects the proper amount of oil into the fuel system
The VRO pump incorporates circuit in the electrical module that warns the operator of "NO OIL" situation
W The 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 diaphragm
The carburetors distribute and meter the fuel to the engineThey control the engine speed and power output by varying the intake charge densityTo react correctly to wide range of operating conditions, the carburetors have several discrete fuel mixing circuitsOn electric start models, mixture enrichment for cold starting and running is provided by solenoid operated fuel primer valveWhen activated at the key switch, the valve diverts some VRO output directly to the intake manifold