Flushing System Mie (Inboard) - Except 454 Mag Mpi Horizon - Mercury MerCruiser MCM 454 Mag MPI Service Manual

MAINTENANCE

Flushing System MIE (Inboard) - Except 454 Mag MPI Horizon

If boat is in the water, seacock, if so equipped, must remain closed until engine is
to be re-started, to prevent water from flowing back into cooling system and/or boat.
If boat is not fitted with a seacock, water inlet hose must remain disconnected and
plugged (to prevent water from flowing back into cooling system and/or boat). As
a precautionary measure, attach a tag to the ignition switch or steering wheel of the
boat with the warning: Open seacock or reconnect water inlet hose before starting
engine.
IMPORTANT: If a seacock is to be installed for this purpose, valve used must have
an internal cross-sectional area equal to or greater than water inlet hose to prevent
restricting water flow during normal operation. A 1-1/4 in. (32 mm), or larger, brass
ball valve or gate valve is recommended.
Boats with water lift type exhaust collectors or mufflers: Engines must be running
when flushing the cooling system to properly drain. If the engine is not run during
flushing, the flushing water can fill up the collector or muffler and back up into the
exhaust manifolds. The water can then enter the internal parts and cause serious
damage.
1. If boat is in water, close seacock, if so equipped, or disconnect and plug seawater inlet
hose to prevent seawater from entering boat.
2. Remove inlet hose from seawater pickup pump.
3. Using an adaptor, connect a hose from a water tap to seawater pump inlet.
4. Partially open water tap (approximately 1/3 maximum). Do not use full water pressure.
5. Place the remote control lever in neutral position and start engine.
Index Index
Page 1B-26
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b
a - Seawater Inlet Hose
b - Seawater Outlet Hose
CAUTION
CAUTION
a
SERVICE MANUAL NUMBER 23
75533
90-861326--1 MARCH 1999