1992 Johnson Evinrude "EN" 40 thru 55 Service Manual, P/N 508143, Page 62Get this manual
Description of Fuel System
LJ operated by changes in crankcase
r:;l 1The fuel pump is of the diaphragm-displacement type and is pressureAlternately, suction and pressure in the crankcase are transmitted to the pump diaphragm
f21 2The carburetors meter and distribute the fuel consumed They control engine speed and power output by varying the intake charge densityTo react correctly to wide range of operating conditions, the carburetors have multiple fuel mixing circuitsf31 3The unit is combination mechanical fuel and oil pump, powered by crankcase pressure and vacuum pulses, which responds to various engine power settings by injecting the proper amount of oil into the fuel systempump incorporates circuit The of "no oil" situation