1990 Johnson Evinrude "ES" Colt/Junior thru 8 Service Manual, P/N 507870, Page 61Get this manual
Description of System r:jl 1The fuel pump is of the diaphragm -displacement type, and
is operated by changes in crankcase pressure Alternately, suction and pressure in the crankcase are transmitted to the pump diaphragm
2 The carburetor meters and distributes the fuel consumed