2009 Yamaha F40 Outboard Service Manual, Page 282Get this manual
Shimming
If the shim thickness adjustment value is positive, the current shim thickness must be increased by that amount and, if the value is negative, the current shim thickness must be decreased by that amount The gray-colored area on the selection chart indicates the range of the specified backlashShimming is not required if the measured backlash is within the gray-colored area The values for the shim thickness adjustments specified in the selection chart are intended to achieve the median value within the range for the specified forward or reverse gear backlash The table below the selection chart shows the shim thickness adjustments for the points marked on the chart4Calculate the new reverse gear shim thickness (T2) in the same way as in the exampleCalculation formula: New reverse gear shim thickness (T2)Current reverse gear shim thicknessShim thickness adjustment Example: If the current reverse gear shim thickness is 0.62 mm and the shim thickness adjustment is 0.22 mm, then (T2)0.62 mm(0.22) mm0.62 mm 0.22 mm0.40 mm Available shim thicknesses: 0.10, 0.12, 0.15, 0.18, 0.30, 0.40, and 0.50 mm