Honda BF15D BF20D Outboard Motors Shop Manual., Page 91Get this manual
fSHIM SELECTION When replacing the gear case, vertical shaft, andor taper roller bearingselect the shim as following:
THRUST WASHER (3.5 mm thickness)
] PINION GEAR SHIM
[4] 40 mrn SHIM
[6] FORWARD BEVEL GEAR
[5] TAPER ROLLER BEARING
PINION GEAR SHIM
Select the shim according to the engagement mark on the gear caseEngagement mark[I] GEAR CASE
Thrust washer
Thickness 1.53 rnm (0.060 in) 1.56 mm (0.061 in)