2006 SD Johnson 4 Stroke 9.9-15HP Outboards Service Manual, Page 216Get this manual
GEARCASE SHIMMING ADJUSTMENTS
Pinion GearReverse Gear
Check the amount of backlash between the pinion gear and forward gearInstall the propeller shaft, reverse gear, and bearing housing assemblyTighten retaining screws to 72 inIbs(8 Nm)Check the amount of backlash by slightly rotating the driveshaft by hand Backlash should not be less than between the pinion and forward gearsIf backlash is less, reduce reverse gear back-up shim thickness
Propeller Shaft Thrust Play
After adjusting all gear positions, measure the propeller shaft playIf not within the following values, make shim adjustment: Propeller shaft thrust play: 0.008 to 0.016 in(0.2 to 0.4 mm)