Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 253Get this manual
56 Measure distance (a) between top of nut (b) and bottom 01 bolt head (c)Increase distance (a) by in(25.4mm)Insert tool into reverse gear assemblyPosition gauging block under pinion gearpositionand tighten collar retaining bolt
10Remove tooltaking care not to change gauging blocl
11 Insert tool in to reverse gear assemblyPosition the number 4" Ilatol gauging block under pin ion gear
Rotate drive shaft ten revolutions to seat upper tapered roUer bearingaGaugirlg Btock