Yamaha F100B F100C Outboards Factory Service Manual, Page 176Get this manual
Lower unit
3Install the special service tool so that it pushes against the propeller shaft
3Select the reverse gear shim(s) (T2) as followsCalculated numeral at 1100 place 1, 3, 4, 6, 7, 9, 10 Rounded numeral 10
Available shim thicknesses: 0.10, 0.12, 0.15, 0.18, 0.30, 0.40, and 0.50 mm Example: If "T2" is 0.53 mm, then the reverse gear shim is 0.55 mmIf "T2" is 0.50 mm, then the reverse gear shim is 0.50 mm
NOTE: Tighten the center bolt while turning the drive shaft until the drive shaft can no longer be turnedBearing housing puller claw 1: 90890-06502 Stopper guide plate 2: 90890-06501 Center bolt 3: 90890-06504 4Install the backlash indicator onto the drive shaft (22.4 mm [0.88 in] in diameter), then the dial gauge onto the lower unit5Set the lower unit upside down