2003 ST 4 Stroke 9.9/15HP Johnson outboards Service Manual, Page 124Get this manual
POWER UNIT INSPECTIONSERVICING
Valve Stem End Length
Measure: The stem and length
Vernier calipers
Valve stem and length Service limit: IN and EX 2.2 mm (0.09 in)
If lower than the service limitReplace
Valve Stem End Runout
Measure: Valve stem runout (Total indicator reading)
Vernier calipers Magnetic standblock