Mercury Mariner 25HP 4-Stroke Outboard Service Manual 1997, Page 104Get this manual
Fuel Pump Operation 1The fuel pump is diaphragm pump which is mechanically driven off of the rocker arm2The black mounling block (insulator) helps prevent vapor lock3If the engine runs out of fuelor has restriction preventing adequate fuel flow, the pump will make "clicking" noise
Fuel Pump Disassembly
1Remove screws to separate pump cover, cover seal, and diaphragm, from pump bodyc
Fuel Pump Removal
1Cut sta-straps and remove inlet and outlet hoses