Yamaha F100B F100C Outboards Factory Service Manual, Page 169Get this manual
Drive shaft and lower case (F100B) Installing the water pump and shift rod
1Install the shift rod assembly 13Install the Woodruff key into the drive shaft4Align the groove on the impeller with the Woodruff key 6, and then install it to the drive shaft
5Install the washers 7, wave washer 8, spacer 9, and collar to the drive shaft