Mercury Mariner 4 and 5HP 4-Stroke Outboards Service Shop Manual 1999, Page 81Get this manual
FU EL PUMP
Fuel Pump Disassembly
1Remove screws and separate the pump cover from the pump body
aPu mp CoverGasketPump BodyScrew (4)
2Remove diaphragm by pushing in the plunger while turning the diaphragm 90 clockwise or counterclockwiseaDiaphragmSpringPump BodySpring