1971 Johnson 4HP Outboard Motors Service Manual, Page 22Get this manual
FUEL PUMP AND FILTER Before replacing fuel remove and install new filter screen and gasketSee Figure 3-17Also move the fuel line from the fuel tank and blow through all passages and lines with compressed air to sure they openThis the cause of inadequate fuel delivery, and if so, would eliminate unnecessary replacement of the fuel If this cedure does not correct the trouble fuel is malfunctioning and should replaced
NOTE It is recommended that new fuel filter screen and gasket installed when servicing the filter and assembly
REASSEMBLY OF FUEL PUMP AND FILTER
Reassemble the fuel filter to in the reverse order of disassembly being careful that lip of screen faces fuel Attach fuel gasketto power head, using new