1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 114Get this manual
Acceleration Pump Fuel Flow Circuit for Four Cylinder Engines
#2 CARBACCELERATOR PUMP LARGE FUEL FILTER
+4.0 PSI SMALL FUEL FILTER +5 .0 PSI #3 CARB
CYL#3 FUEL PUMP CHECK VALVES LOCATED IN CYLINDER BLOCK TRANSFER PORTS (UNSEAT AT 1114 PSI .5 PSI