1988-1992 Mercury Force 5HP Outboards Service Manual, Page 209Get this manual
2 Inspect propeller shaftLook for: Wear or distortion around clutch slot (A) and propeller pin hole (8)Sharp burrs or nicks; remove with file or emery cloth Cracks on splines (C)
NOTE: Do not remove excessive metal from shaftInspect clutch spring Check length: 2.4 in(6.2 cm)Check for straightness by rolling on flat surfaceInspect clutch Check for cracks at shear pointsCheck for rounding at area (A) that contacts clutch dogs on forward gear