1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 66Get this manual
CARBURETOR SYNCHRONIZATION 1Remove sound box cover2Loosen cam follower adjustment screw3Loosen synchronizing screws4Look into throats of carburetors and make sure all throttle shutters are completely closed5Apply light down pressure on carburetor synchronizing shaft and tighten synchronizing screws from top to bottom6Recheck throttle shutters and make any necessary adjustment7Hold throttle arm so that the throttle stop screw is against stop8Place roller of cam follower against throttle cam and adjust throttle stop screw to align raised mark of throttle cam with center of cam follower rollerTighten locknutaRollerThrottle CamScrew