1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 364Get this manual
3Adjust cable barrel to attain the same length between cable barrel and hole in end of cable guide as exists between barrel retainer and shift actuator stud, with slight preload toward reverse4Place end of shift cable on shift actuator stud then place plastic washer on stud and secure with locknut5If used, remove tape from control handle6Check shift cable adjustment as follows: aShift remote control into forward gearNow, check prop shaftThe shaft should not be able to turn counterclockwiseIf it does, adjust cable barrel closer to cable end guidebShift remote control into neutralThe prop shaft now should turn freely without dragIf not, adjust cable barrel away from cable end guideRepeat steps and bcShift remote control into reverse as the prop shaft is rotated by handThe prop shaft should not be able to turn in either directionIf it does, adjust cable barrel away from cable end guideRepeat steps thru cdShift remote control into neutralThe prop shaft should turn freely without dragIf not, adjust cable barrel closer to cable end guideRepeat steps thru d Throttle Cable Installation and Adjustment to Engine