1998 Mercury 9.9/15HP 4-stroke outboards factory service manual, Page 116Get this manual
FUEL PUMP
Fuel Pump Reassembly
1Install diaphragm, plunger, springs and o-ring
a-Diaphragm b-Spring-Diaphragm c-Pin d-Pump Base e-Spring-Plunger f-Plunger 2Rotate plunger on body to align slots3Compress plunger and install pin