2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 148Get this manual
Lower unit Available shim thicknesses: 0.10, 0.12, 0.15, 0.18, 0.30, 0.40, and 0.50 mm 7Remove the special service tools, and then install the water pump assembly
4Install the backlash indicator onto the drive shaft (20 mm [0.79 in] in diameter), then the dial gauge onto the lower unit
NOTE: Install the dial gauge so that the plunger contacts the mark on the backlash indicatorBacklash indicator rod 3: YB-06265 Backlash adjustment plate 4: YB-07003 Dial indicator gauge 5: YU-03097 Magnetic base stand 6: YU-A8438 5Slowly turn the drive shaft clockwise and counterclockwise and measure the backlash when the drive shaft stops in each directionForward gear backlash: 0.280.63 mm (0.01100.0248 in) 6Add or remove shim(s) if out of specificationForward gear backlash Less than 0.28 mm (0.0110 in) More than 0.63 mm (0.0248 in) M: Measurement Shim thickness To be decreased by (0.46 M) 0.56 To be increased by (M 0.46) 0.56