Yamaha 25BMH 30HMH Factory Service Manual, Page 294Get this manual
PROPELLER SHAFT HOUSING
3Install: Reverse gear Reverse gear shim(s) Ball bearing Propeller shaft housing 4
NOTE: Before press-fitting the ball bearing, install the reverse gear shim(s) Install the ball bearing with its manufacturer's marks facing the reverse gearCAUTION: Place suitable base under the gear to protect it from damages