2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 147Get this manual
ShimmingBacklash NOTE: Tighten the nut four turns after it contacts the springForward gear shim selecting tool: YB-34446-1 2, YB-34446-3 3, YB-34446-5 4, YB-34446-7 3Measure the clearance (M) between the gauge pin and the press plate Backlash
1Remove the water pump assembly
Measuring the forward gear backlash
NOTE: Do not remove the oil seal housing in this procedure2Set the gear shift to the neutral position at the lower unit
4Select the forward gear shims (T1)
Shift rod push arm: YB-06052 3Install the special service tools so that it pushes against the propeller shaft