COOLANT SYSTEM
Thermostat Components and Functions
7-18
6LY3 Service Manual
© 2007 Yanmar Marine International
Inspecting the Thermostat
Remove the thermostat cover
(Figure 7-20, (3))
on the side of the coolant tank and take out the
thermostat.
Clean off the scale and rust and inspect.
Replace if the performance characteristics have
changed, or if the spring is broken, deformed or
corroded.
Figure 7-20
Figure 7-20
1 – Thermostat
2 – Gasket
3 – Thermostat Cover
Testing the Thermostat
1. Place the thermostat
(Figure 7-21, (2))
in a
beaker of fresh water and heat it on an electric
stove. The thermostat is functioning normally if
it starts to open between 69 and 73°C
(156 and 163°F), and opens to 10 mm
(0.4 in.) or more at 85°C (185°F). Replace the
thermostat if it is not functioning normally.
Figure 7-21
Figure 7-21
1 – Thermometer
2 – Thermostat
2. The thermostat should be inspected every 500
hours of operation. It should be inspected
sooner if the engine temperature rises
abnormally or white smoke is emitted any time
during engine operation.
3. Replace the thermostat every year or 2000
hours of operation, whichever comes first.
000621
8
(1)
(2)
(
3
)
Thermostat Specifications
Valve Opening
Temperature
*
*
Valve opening temperature is stamped on the
flange.
Full Open Lift
69-73°C (156-163°F)
10 mm (0.4 in.) at
85°C (185°F) or more
000619
8
(1)
(2)
