Yamaha Marine Outboards Factory Service / Repair/ Workshop Manual 225G 250B L250B, Page 226Get this manual
BACKLASH (COUNTER ROTATION MODELS)
(9) Turn the shift rod into the reverse position with the shift rod wrench(10) Slowly turn the drive shaft clockwise and counterclockwiseWhen the drive shaft stops in each direction, measure the backlashNOTE: When measuring the reverse gear backlash, turn the shift rod wrench towards the reverse position with force2Adjust: Reverse gear shim Remove or add shim(s)Reverse gear backlash Less than 0.64 mm (0.025 in) More than 0.93 mm (0.037 in) M: Measurement Shim thickness To be decreased by (0.79 M) 0.78 To be increased by (M 0.79) 0.78