2003 ST 4 Stroke 9.9/15HP Johnson outboards Service Manual, Page 173Get this manual
LOWER UNIT INSPECTION
INSPECTION
If any component is worn excessively, cracked, defective or damaged in any way, it must be replaced
Thoroughly wash all metal components with cleaning solvent and dry them off with compressed air
AWARNING
Wear safety glasses when using compressed air
PROPELLER
Inspect: Propeller Bent, chippingbreak, wearReplace Propeller spline Wear, damageReplace Propeller bush Defective, slippingReplace