1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 62Get this manual
11Holding throttle arm against throttle stop screw, adjust cam follower, so that clearance of 0.005 in- 0.020 in(0.1270.508 mm) exists between roller of cam follower and throttle camTighten set screw securing cam follower0.005 0.020
TIMING ADJUSTMENTS
CAUTION
Engine is timed while cranking engine with starter motorTo prevent engine from starting when being cranked, all spark plugs must be removed, except no1 (top) cylinder plug
NOTE: If initial timing adjustments are made without engine running, then final timing checks should be made with engine running due to timing advance characteristics of ignition systemMinimum engine RPM required to check maximum timing advance is 3000 RPMIDLE TIMING ADJUSTMENT 1Connect timing light to no1 (top) spark plug52472
WARNING
Before cranking engine, keep clear of propeller as it may rotate2Shift engine to "Neutral"IMPORTANT: To accurately time engine at cranking speed, fully charged battery must be used