Mercury Mariner 4 and 5HP 4-Stroke Outboards Service Shop Manual 1999, Page 83Get this manual
FUEL PUMP
Fuel Pump Reassembly
1Align the recess in the stopcheck valve and plate with the projection on the pump cover
aCheck ValvePlateAlign Recess On Back Side of Plate With ProjectionScrew (2) 2Align the slot in the plunger with the projection in the pump body3Assemble the plunger, springs and diaphragm to the pump body4Lock the diaphragm in place by Setting the foot of the diaphragm into the plunger slot and rotating the diaphragm 90