454 Mag Mpi Horizon Models - Mercury MerCruiser MCM 454 Mag MPI Service Manual

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SEAWATER COOLED MODELS

If boat is in the water, seacock (if equipped) must be left closed until engine is to

be restarted to prevent water from flowing back into cooling system. If boat is not

fitted with a seacock, water inlet hose must be left disconnected and plugged, to

prevent water from flowing into cooling system and/or boat. As a precautionary

measure, attach a tag to the ignition switch or steering wheel with the warning that

the seacock must be opened or the water inlet hose reconnected prior to starting

5. Shut off tap water. Remove flushing connector from pump inlet. Refer to preceding

precautionary statement and then follow instructions "a" or "b."

a. If equipped with seacock: Reconnect water inlet hose and tighten hose clamp

b. If NOT equipped with seacock: Unplug and reconnect seawater inlet hose accord-

454 Mag MPI Horizon Models

Do NOT start engine at any point in this procedure. If boat is in the water, starting

engine during this procedure will pull in seawater. If boat is out of the water, starting

engine may damage the seawater pump.

1. Remove blue cap from hose fitting.

2. Attach hose to the hose fitting.

3. Turn on water to highest pressure.

4. Attach hose fitting to engine flush fitting on exhaust elbow.

5. Allow engine to flush for 5 minutes.

6. Attach to next engine, if equipped, and repeat procedure.

7. Remove hose fitting from the engine flush fitting.

8. Turn off water.

9. Remove hose fitting from hose.

10. Replace blue cap on hose fitting.

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securely. Open seacock accordingly.

ingly. Tighten hose clamp securely.

Hose Fitting

Flush Adapter

SERVICE MANUAL NUMBER 23

90-861326--1 MARCH 1999

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