181
COOLING SYSTEM
ENGINE TEMPERATURE CHECK
9
IMPORTANT: If you get low or in accurate read-
ings with a digital pyrometer, coat the probe loca-
tion with Thermal Joint Compound, P/N 322170.
IMPORTANT: Digital pyrometer or tempera ture
gun measu rements may be slightly lower th an
software temperature readings.
Idle Operating Temperature
Troubleshooting (Below Range)
If en gine IDL E te mperature is below operating
range, 155°F ± 5°F (68.3°C ± 3°C), check thermo-
stat and pressure relief valve operation.
Thermostat Inspection
Check p osition o f thermost at seal and ho w ther-
mostat seals against cylinder head. Seal mu st be
properly fitted to flange of thermostat.
Check thermost at for cracks, hea t damage, or
signs of corrosion. Check for proper operation.
Thermostat opens at 143°F (62°C).
Refer to THERMOSTAT SERVICING on p. 182.
Pressure Relief Valve Inspection
The pressu re re lief va lve should b e closed at
IDLE speed. W ater should no t flo w past th e
plunger and seal.
Start the outboard and check IDLE operating tem-
perature.
If IDLE temperature is too low , ch eck pressure
relief valve plunger and seal for damage or debris
that could prevent t he va lve from closing com-
pletely.
If IDLE temperature is still below ope rating range,
replace pressure r elief valve a ssembly an d
plunger seal.
To test p ressure relief valve opera tion, monitor
temperature at th e thermostat housing with Tem-
perature Gun, P/N 772018, or digital pyrometer.
Confirm normal IDLE operating temperature.
Slowly increase engine sp eed from IDLE, up
through 2500 RPM.
Engine temperature should decrease from normal
IDLE temperatures as pressure relief valve opens.
Valve should open between 1800-2200 RPM.
If temperature decreases at a lower RPM, replace
pressure relief valve assembly.
Refer to PRESSURE RELIEF VALVE SERVIC-
ING on p. 183.
Thermostat housing 008345
1. Thermostat seal 006401
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