2003 ST 4 Stroke 9.9/15HP Johnson outboards Service Manual, Page 120Get this manual
POWER UNIT INSPECTIONSERVICING
INSPECTIONSERVICING
NOTE: If any component is found to be excessively worn, cracked, damaged or defective in any way, it must be replaced
Cylinder Head
Decarbon: Combustion chamber wall Measure: Cylinder head distortion (gasket surface)
Thickness gauge Straight gauge