2004 SR Johnson 4 Stroke 9.9-15HP Outboards Service Manual, Page 45Get this manual
PERIODIC MAINTENANCE CYLINDER COMPRESSION
CYLINDER COMPRESSION
Compression pressure specification (with decompression system) Standard: Approx400 kPa (4.0 kgcm57 psi) with recoil starting
The above specification is guideline only, not absolute service limitsLow compression pressure can indicate one or more of the following: Excessively worn cylinder wall Worn-down piston or piston rings Piston rings stuck in grooves Poor seating of valves Ruptured or otherwise defective cylinder head gasket