229
COOLING SYSTEM
ENGINE TEMPERATURE CHECK
9
Typical pyrometer temperature displays at IDLE
speed should be 150°F ± 20°F (66°C ± 11°C).
IMPORTANT: If you get low or inaccurate read-
ings during these tests, coat the probe location of
the digital pyrometer with a liberal amount of
Thermal Joint Compound, P/N 322170.
If engine temperature tests within range, but the
SystemCheck gauge indicates a “WATER TEMP”
warning, refer to WATER TEMP/ HOT Circuit
Test on p. 146.
Idle Operating Temperature
Troubleshooting (Below Range)
If engine temperature is below operating range,
check pressure relief valve and thermostat opera-
tion. Remember, cold running outboards prevent
spark plugs from achieving proper operating tem-
peratures and may decrease spark plug life.
Pressure Relief Valve
The pressure relief valve should be closed at
IDLE speed. Water should not flow past the
plunger and seal.
Check for damage or debris that could prevent
the valve from closing completely. Replace pres-
sure relief valve if necessary.
Refer to PRESSURE RELIEF VALVE SERVIC-
ING on p. 233.
Thermostats
If IDLE temperature is still below operating range,
inspect thermostats and thermostat seals.
Check position of thermostat seal and how ther-
mostat seals against cylinder head. Seal must be
properly fitted to flange of thermostat.
Check thermostat for cracks, heat damage, or
signs of corrosion. Check for proper operation.
Thermostat opens at 143°F (62°C).
Refer to THERMOSTAT SERVICING on p. 233.
005390
1. Thermostat seal 005392
1
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