1998-2006 Yamaha F20/F25 Outboards Service Manual, Page 259Get this manual

! SHIMMING (EXCEPT FOR USA AND CANADA)
Forward gear shim

Find the forward gear shim thickness (T1) by selecting shims until the specified measurement (M) is obtained with the special tool
1Measure: Measurement (M) Shimming plate:

90890-06701
Digital caliper:

• ATV
• Jet Ski
• Outboard Motors
• Personal Watercraft
• Snowmobiles
• Stern Drives