Yamaha 25BMH 30HMH Factory Service Manual, Page 324Get this manual
BACKLASH BACKLASH
NOTE: Do not install the water pump components when measuring the backlash Measure both the forward and reverse gear backlashes If both the forward and reverse gear backlashes are larger than specification, the pinion gear may be too high If both the forward and reverse gear backlashes are smaller than specification, the pinion gear may be too low