Installation - Mercury MerCruiser MCM 454 Mag MPI Service Manual

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SEAWATER COOLED MODELS

IMPORTANT: When performing procedures "d"-"f," water must be agitated thor-

oughly to obtain accurate results.

d. Plug in tester and observe temperature at which thermostat opens (thermostat

e. Continue to heat water until a temperature 25 F (14 C) above temperature specified

g. Replace a thermostat that fails to meet all of the preceding tests.

Installation

1. Clean gasket surfaces on thermostat housing and intake manifold.

IMPORTANT: Gasket has continuity rivets. Do not coat with Quicksilver Perfect Seal,

or Audio Warning Temperature Switch may not work properly.

2. Place O-ring in the thermostat housing. Be certain it is positioned properly in housing.

3. Place thermostat in thermostat housing with thermostatic element end toward housing

bottom, as shown.

4. Align sleeve with groove in thermostat housing bore and install sleeve into housing.

5. Coat both sides of new thermostat housing gasket with Quicksilver Perfect Seal and

position on intake manifold.

6. Reinstall thermostat housing and torque screws with lockwashers to 30 lb-ft (41 Nm).

7. Reconnect hose(s) to thermostat housing. Tighten hose clamps securely.

8. Start engine and inspect for leaks.

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drops off thread). Thermostat must open at specified temperature stamped on ther-

on thermostat is obtained. Thermostat valve must be completely open at this tem-

Unplug tester and allow water to cool to a temperature 10 F (5 C) below specified

temperature on thermostat. Thermostat must be completely closed at this tempera-

Thermostat (Stainless Steel)

SERVICE MANUAL NUMBER 23

90-861326--1 MARCH 1999

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