1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 183Get this manual
13Remove components from propeller shaft14Replace cam follower if worn or pitted15Replace sliding clutch if jaws are rounded or chippedRounded jaws indicate one or more of the following: aImproper shift cable adjustmentbEngine idle speed too high while shiftingcShifting from neutral to reverse (or forward) too slowly 16Check bearing surfaces of propeller shaft for pitting or wearIf shaft is worn or pitted, replace shaft and corresponding bearing17Replace propeller shaft if any of the following exist: aSplines are twisted or wornbOil seal surface is groovedcShaft has noticeable "wobble" or is bent more than 0.009 in(0.228mm)Prop shaft trueness should be measured with dial indicator with prop shaft on V-blocks