Mercury Force 9.9, 15HP Outboards Service Manual, Page 171Get this manual
4Inspect cl utch Check for cracks at shear pointsCheck for rounding at area that contacts cl utch dogs on forward gearCheck uncompressed length of clutch springIt should be 2-716 in(63 mm) longCheck straightness of clutch spring by rolling on flat surface 5Inspect shift pin and clutch shift cam for wear Shift cam will wear on faceNOTE: Excessive wear on crests (A) may allow motor to slip out of gear Length of shift pin should be 1.709 0.003 in(43.40 0.07 mm)