Changing Coolant; Closed Cooling Section; Coolant Recommendations; Change Intervals - Mercury MerCruiser MCM 454 Mag MPI Service Manual

SERVICE MANUAL NUMBER 23

Changing Coolant

For information and procedures on draining the seawater cooling system of Seawa-
ter Cooled (Raw-water) Cooled Models, refer to SECTION 6A. For information and
procedures on draining the Seawater Section of Closed Cooling (Coolant) Models
refer to SECTION 1B. For cold weather or extended storage, refer to SECTION 1B.

Closed Cooling Section

Closed cooling section of closed cooling system should be kept filled year-round with
recommended coolant solution. Do not drain closed cooling section for storage, as this will
promote rusting of internal surfaces. If engine will be exposed to freezing temperatures,
make sure that closed cooling section is filled with Extended Life 5/100 Coolant or an
ethylene glycol antifreeze and water solution, mixed to manufacturer's recommended
proportions, to protect engine to lowest temperature to which it will be exposed. If necessary,
change coolant.

Coolant Recommendations

Alcohol or Methanol base antifreeze or plain water are not recommended for use in
fresh water section of cooling system at any time.
NOTE: All factory installed closed cooling systems come filled with Extended Life 5/100
Coolant. This antifreeze requires draining and replacing every five years or 1000 hour of
operation, whichever comes first. The color of this antifreeze is orange. For best results any
"top-off" fluid used should be Extended Life 5/100 Coolant. If Extended Life 5/100 Coolant
is unavailable, any type of ethylene glycol based antifreeze may be used, but it will require
the draining and replacing of the coolant every two years or 400 hours of operation, whichev-
er comes first.
In areas where the possibility of freezing DOES NOT exist, it is permissible to use a solution
of rust inhibitor and water (mixed to manufacturer's recommendations).

Change Intervals

If the closed cooling system is factory installed, drain and flush coolant from the closed cool-
ing system at least every five years or 1000 hours of operation, whichever comes first. It
should also be changed whenever exhaust gases have entered the system.
If the system is not factory installed or has had anti-freeze other than Extended Life 5/100
Coolant added, it must be changed every two years or 400 hours of operation, whichever
comes first.

Draining Instructions

Allow engine to cool before removing pressure cap. Sudden loss of pressure could
cause hot coolant to boil and discharge violently. After engine has cooled, turn cap
1/4 turn to allow any pressure to escape slowly, then push down and turn cap all the
way off.
IMPORTANT: A wire should be inserted into drain holes to ensure that foreign
material is not obstructing the drain holes. On some models with two piece petcock,
removal of petcock may be required so that wire can be inserted completely into drain
hole.
Index
90-861326--1 MARCH 1999
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CLOSED COOLED (FRESH WATER) MODELS
NOTICE
CAUTION
WARNING
Page 6B-13