Honda BF20A-BF25A, BF25D-BF30D Outboard Motors Shop Manual., Page 143Get this manual
7SHIM SELECTION
When replacing any parts in the lower unit, refer to the Lower Unit Shimming Guide below
LOWER UNIT SHIMMING GUIDE
REPLACEMENT PART Gode P
SHIMMING OPERATION REQUIRED P, F, R, and BL
Operation
Pinion Gear Shim
Gear Case Vertical Shaft, Bearing, and or Pinion gear
1 Forward Bevel Gear Shim 1
Reverse Bevel Gear Shim Backlash Check-Adjust