Mercury Mariner 200, 225 Optimax Outboards Service Manual, 90-855348, Page 432Get this manual
Shift Spool Assembly INSPECTION
1Clean the assembly with suitable solvent and dry the parts using compressed air2Inspect the shift spool assembly for damageSmall nicks and burrs may be smoothedIf any parts are damaged or worn beyond repair it will be necessary to replace the complete shift spool assemblyIndividual parts are not available for the assembly3Inspect the shift spool for wear in the area where the shift crank comes into contact
4Inspect to insure that the spool spins freely (it may be helpful to lightly tap the forward [castle nut] end of the shift spool shaft against firm surface to align the internal parts)5Inspect to insure that the spool has no more than 0.002-0.010 (0.051-0.254 mm) end play