1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 117Get this manual
Maintenance Periodically check fuel line and primer bulb for cracks, breaks, restrictions or chafingCheck all fuel line connections for tightnessAll fuel line connections must be clamped securelyPrimer bulb assembly has check valves: Fuel inlet (toward tank) and fuel outlet (toward engine)The fuel inlet valve allows fuel to fill primer bulb but closes to prevent fuel from returning to tank when bulb is squeezedThe fuel outlet valve opens when primer bulb is squeezed to allow fuel flow to carburetor, but closes as bulb is released to prevent fuel from returning to primer bulbFUEL LINE CLAMP REMOVAL AND INSTALLATION