1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 383Get this manual
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12 Drive out drift pin and remove throttle gear from throttle arm 3 Slide cover and friction device onto throttle arm51604 Throttle Arm Gear Throttle Friction Device Cover
51602 GearDrift Pin