Yamaha F115A Service Manual page 438

LOWR
BACKLASH (REGULAR ROTATION MODELS)
2. Adjust:
• Reverse gear shim
Remove or add shim(s).
Reverse gear
backlash
Less than
0.86 mm (0.034 in)
More than
1.26 mm (0.050 in)
M: Measurement
6-69
E
Shim thickness
To be increased by
(1.06 – M) × 0.58
To be decreased by
(M – 1.06) × 0.58