2009 Yamaha F40 Outboard Service Manual, Page 269Get this manual
Lower unit
Measuring the forward and reverse gear backlash before disassembly
1Install the lower unit onto repair stand2Remove the water pump assemblySee "Removing the water pump" (8-5)3Set the gear shift to the position
Shift rod push arm a: YB-06052 4Install the special service tools and c, and then tighten the center bolt temporarily
Center bolt (shimming): Nm (0.5 kgfm,3.7 ftlb) 8Turn the lower unit upright9Install the special service tool onto the drive shaft at the lowest possible position, the point where the shaft diameter is 16.0 mm (0.63 in)10Wrap layers of tape around the drive shaft