2000-2005 Yamaha F40B Outboard Service Manual, Page 322Get this manual
SHIMMING (FOR USA AND CANADA)
2Adjust: Shim thickness (T3) Remove or add shim(s)Available shim thickness 0.10, 0.12, 0.15, 0.18, 0.30, 0.40 and 0.50 mm
(MO)(M) should be as close to "0" as possible
SELECTING THE FORWARD GEAR