Mercury MerCruiser D2.8L D-Tronic Service Manual page 752

CLOSED COOLING SYSTEM
4. Following the manufacturers recommendations for usage, check opening and closing
temperature. The thermostat opens when it drops off of thread using a tester.
Thermostat must open at specified temperature stamped on thermostat.
Typical Thermostat Tester In Use
IMPORTANT: Refer to specifications and note that the two thermostats have different
opening temperatures.
5. Continue to heat water until a temperature 14 degrees C (25 degrees F) above opening
temperature is obtained. Thermostat valve must be completely OPEN at this
temperature.
6. Unplug tester and allow water to cool to a temperature 5 degrees C (10 degrees F) below
specified opening temperature. The thermostat must be completely CLOSED at this
temperature.
7. Always replace a thermostat that fails to meet all of the preceding tests with one of the
same temperature specification.
Page 6B-24
a - Thermometer
b - Nylon String
c - Thermostat
b
a
c
SERVICE MANUAL NUMBER 22
72675
90-860074--1 FEBRUARY 2002