1988 Johnson/Evinrude "CC" 40 thru 55 Models Service Manual, Page 80Get this manual
Description of Fuel System 1The 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
2The carburetor(s) meter and distribute the fuel consumedThey control engine speed and power output by varying the intake charge densityTo react correctly to wide range of operating condition, the carburetors have multiple fuel mixing circuits
f3l335A, 40, 50 Remote Control modelsThe 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 system units incorporate circuit that warns the operator of "no oil" situation