Mercury 25 EFI Service Manual page 305

Water Flow Diagram
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f
g
i
Thermostat
Inspect the thermostat. Replace if damaged, seized, or corroded.
Thermostat Measurement Test
1. Tie a piece of thread or other nonconductive material onto the thermostat.
2. Suspend the thermostat in cold water.
3. Suspend a thermometer in the water.
IMPORTANT: Do not allow the thermometer to contact the heating surface of the container. An inaccurate temperature
reading may result.
4. Slowly heat the water while observing the thermostat and thermometer.
90-8M0105568 eng MARCH 2016
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c
k
a -
d
b -
c -
d -
e -
f -
g -
h -
i -
j -
k -
e
h
j
22571
© 2016 Mercury Marine
Fuel cooler
Cylinder head
Thermostat
Cylinder block
Adapter plate
Water pump indicator
Idle relief
Water tube
Driveshaft housing
Water pump
Water inlet
Cooling System
Page 4D-3