1998-2006 Yamaha F20/F25 Outboards Service Manual, Page 269Get this manual
2Adjust: Forward gear backlash Remove or add shim(s) Forward gear backlash Less than 0.31 mm (0.021 in) More than 0.72 mm (0.028 in)
Shim thickness To be decreased by (0.51M) 0.49 To be increased by (M.51) 0.49
Available shim thickness: 1.0,1.1, 1.2, 1.3, and 1.4 mm
Reverse gear 1Measure: Reverse gear backlash Out of specification 7 AdjustReverse gear backlash: 0.931.65 mm (0.0370.065 in)
Measuring steps: Set the shift shaft in the reverse posi tion Load the reverse gear by installing the propeller without the collar CD and then tighten the propeller nutPropeller nut: Nm (0.5 kg, 3.6 ft Ib)