Thermostat Test; Temperature Switch Test - Mercury 40 Service Manual

Thermostat Test

Wash thermostat with clean water. Using a thermo-
stat tester, similar to the one shown, test thermostat
as follows:
· Open thermostat valve, then insert a thread be-
tween valve and thermostat body. Allow valve to
close against thread.
· Suspend thermostat (from thread) and thermom-
eter inside tester so that neither touches the con-
tainer. Bottom of thermometer must be even with
bottom of thermostat to obtain correct thermostat
opening.
· Fill thermostat tester with water to cover thermo-
stat.
· Plug tester into electrical outlet.
· Observe temperature at which thermostat begins
to open. Thermostat will drop off thread when it
starts to open. Thermostat must begin to open
when temperature reaches 5°F (3°C) above des-
ignated stamping on bottom of thermostat.
· Continue to heat water until thermostat is com-
pletely open.
· Unplug tester unit.
· Replace thermostat, if it fails to open at the speci-
fied temperature, or if it does not fully open.
90-852572R1 JANUARY 1998

Temperature Switch Test

190° F (88° C)
The 190° F (88° C) temperature switch is located in
outer side of cylinder head as shown.
a
a - Temperature Switch
During normal engine operating temperature, the
switch electrical circuit is open. The switch will close
when the temperature reaches 190° F ±8° F (88° C ±
4° C). Reset of the switch to open circuit occurs at
170° F ± 8° F (77° C ±4° C).
To test, place switch end into water with thermometer
and heat to 190° F ±8° F (88° C ±4° C). Take out and
perform ohms test. Compare to specifications. If
switch does not fall within specifications, replace
switch.
56671
POWERHEAD - 4-15