Yamaha Outboard F15A F9.9C, FT9.9D F15 Service Manual, Page 376Get this manual
BACKLASH MEASUREMENT (FT9.9D)
Measurement steps: Load the reverse gear by installing the propeller collar and then tighten the propeller nut8 Set the lower unit upside downPropeller nut: Nm (0.5 mkg, 3.6 ftlb) Attach the backlash indicator onto the drive shaft (12.8 mm in diameter) as shownBacklash indicator: 90890-06706 Attach the dial gauge onto the lower unit and have the dial gauge plunger contact the mark on the backlash indicatorBase plate: 90890-07003 Dial gauge set: 90890-01252 Magneto base: 90890-06705 Slowly turn the drive shaft clockwise and counterclockwise and when the drive shaft stops in each direction, measure the backlash2Adjust: Reverse gear backlash Remove or add shim(s)NOTE: