2009 Yamaha F40 Outboard Service Manual, Page 281Get this manual
Lower unit
Measuring the reverse gear backlash
Spray anti-rust lubricant on the gear and bearings before installationDo not apply gear oil to the partsOtherwise, correct measurements cannot be obtained Keep the parts free from foreign materials, such as dirt or lint When measuring the forward or the reverse gear backlash, use the original bearing and shims1Install the ball bearing and the original shim(s) (T2) onto the reverse gear, and then install the reverse gear assembly into the propeller shaft housingSee "Assembling the propeller shaft housing assembly" (8-9) step 3step 5
Do not reuse shim if deformed or scratched3Determine the reverse gear shim thickness (T2) adjustment using the "Reverse gear shim (T2) selection chart" according to the truncated average (BL2) from "Measuring the reverse gear backlash Example: (BL2)1.25 mm (T2) adjustment0.16 mm from the "Reverse gear shim (T2) selection chart The current shim thickness must be increased by 0.16 mm