Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 206Get this manual
4Measure distance (a) between top of nut (b) and bottom of bolt head (c)5Increase di stance (a) by 1" (25.4mm) 8Insert tool into forward gear assembly; position gauging block under pinion gear as shown9Remove tooltaking care not to change gauging block positionand tighten collar retaining bolt 10.lnsert tool into forward gear assemblyposition the number "4" flat of gauging block under pinion gear
a Gauging Block
6Rotate driveshaft ten revolutions to seat upper tapered roller bearing 7Assemble Pinion Gear Locating Tool (9l -12349A2) as shown; do not tighten coilar retaining bolt at this time