2007-2009 Yamaha F15/F20 Outboard Service Manual, Page 176Get this manual
LOWR Shimming
Lower unit
NOTE: Shimming is not required when assembling the original lower case and inner parts Shimming is required when assembling the original inner parts and new lower case Shimming is required when replacing the inner part(s)
Calculated number 1.141.20 1.211.30
Shim thickness (mm) 1.13 1.20
Available shim thicknesses: 1.13 and 1.20 mm
Selecting the pinion shim
Selecting the forward gear shim