Mercury Mariner 4 and 5HP 4-Stroke Outboards Service Shop Manual 1999, Page 112Get this manual
CYLINDER HEAD
Cleaning and Inspection
Cylinder Head
1Inspect the cylinder head for mineral deposit blockagecorrosion in the wate passage ways, clean any depositscorrosion observed2Inspect the cylinder head for carbon deposits In combustion chamber (use round scraper to clean away deposits)Be careful not to scratch or remove materiala