2003 ST 4 Stroke 9.9/15HP Johnson outboards Service Manual, Page 174Get this manual
LOWER UNIT INSPECTION PROPELLER SHAFT COMPONENTS
Inspect: Push rod Wear, breakReplace Clutch shifter dog Chipping, wear, damageReplace Clutch dog pin Bent, wearReplace Propeller shafUsplines Wear, twistingdamageReplace Measure: Clutch return spring free length
Clutch return spring free length Standard Service limit 70 mm (2.755 in) 68 mm (2.677 in)
If out of specificationReplace