2002/2003 Johnson SN/ST 2 Stroke 3.5, 6 8 HP Outboards Service Manual, PN 5005466, Page 139Get this manual
POWERHEAD OVERHEAT INSPECTION WOT Temperature Increase engine speed to 5000 RPMAt 5000 RPM, the digital pyrometer must not indicate more than 160F (71C)Model ALL WOT Temperature
Inspect the cylinder block and cylinder head for warpage
If engine temperature exceeds 160F (71C), troubleshoot cooling system to determine problem
OVERHEAT INSPECTION
ALL MODELS If the engine has overheated, the following items should be checked for damage Check the water cover and exhaust cover gaskets for leakage Remove the cylinder head Inspect the pistons, rings, and cylinders for damage Check all water passages for damage or restrictionsRefer to INSPECTIONAll ModelsReplace the cylinder head and gasketInspect the thermostat for proper operation (68 models)Check all of the powerhead screws for proper torque