Flushing System - Mercury MerCruiser MCM 4.3L ALPHA Service Manual

MAINTENANCE

Flushing System

If engine is operated in salty, polluted or mineral-laden water, flush seawater cooling system
(preferably after each use) to reduce corrosion and prevent the accumulation of deposits
in the system. Thoroughly flush the seawater cooling system prior to storage.
NOTE: For additional protection against freezing and rust to the exhaust manifolds and
other components, a 50-50 mixture of antifreeze and water can be run through the engine
during Power Package Layup.
1. Install flushing attachment and water hose over the water pickup holes in gear housing.
When flushing, be certain the area around propeller is clear, and no one is standing
nearby. To avoid possible injury, remove propeller.
Do not run engine above 1500 rpm when flushing. Suction created by seawater pick-
up pump may collapse flushing hose, causing engine to overheat.
Watch temperature gauge on dash to ensure that engine does not overheat.
2. Open water tap enough to cool the engine, about ½ of its maximum capacity. Adjust as
required so that the engine does not overheat.
3. With drive in neutral gear, start engine and advance the throttle until the engine reaches
1300 rpm.
IMPORTANT: DO NOT run the engine at idle rpm. Watch engine temperature gauge
on dash. Do not run the engine above 1500 rpm or engine overheating may occur.
4. Run engine for 10 minutes or until the discharge water is clear.
5. Slowly return the throttle to the idle position and turn engine off.
IMPORTANT: DO NOT rapidly advance or return throttle as this can cause water in-
gestion.
Index
Page 1B-18
a - Flushing Attachment
b - Hose
a
b
WARNING
CAUTION
CAUTION
SERVICE MANUAL NUMBER 25
90-861328--1 NOVEMBER 1999
72693