Mercury MerCruiser D2.8L D-Tronic Service Manual page 751

SERVICE MANUAL NUMBER 22
6. Remove thermostats.
Testing
1. Clean thermostats in soap and water to remove any deposits or debris.
2. Inspect thermostats for corrosion or other visible damage.
3. If thermostats are suspected of producing insufficient engine temperature, check
thermostats for leaks by holding them up to lighted background. Light leaking around
the thermostat valve indicates that thermostat is not closing completely and should be
replaced. A few light leaks at one or two points around the valve perimeter is acceptable.
90-860074-1 FEBRUARY 2002
a - Thermostat Housing Cover
b - Thermostat(s)
c - Gasket
a - Perimeter of Valve
a
b
d
c
a
CLOSED COOLING SYSTEM
73973
72717
Page 6B-23