MerCruiser GM4 Service Manual page 311

Torque Specifications
Description
Drain Plugs
Heat Exchanger
End Caps
Reservoir to Thermostat
Housing
Thermostat Cover
Hose Clamps
Heat Exchanger
Mounting Brackets
Lubricants/Sealants
Description
Quicksilver 2-C-4
Marine Lubricant With
Teflon
Quicksilver Perfect Seal
Specifications
Cooling System Capacity
Thermostat
Cap Pressure
Description
There are several configurations of this cooling sys-
tem, but the operation is essentially identical. Basical-
ly, the system is composed of two separate subsys-
tems: the seawater system and the closed cooling
system. The seawater system is similar in function to
the fan used in an automobile because it absorbs
heat (from the closed cooling system) as it passes
through the heat exchanger. The closed cooling sys-
tem is similar in function to the rest of the cooling sys-
tem in an automobile.
Index
90-816462 2-695
lb. in. lb. ft. N m
Securely
190 22
30 41
20 27
S Securely l
Part Number
92-825407A3
92-34227-1
9 (8.5)
143 F(62 C)
14 PSI (97 kPa)
The coolant recovery system keeps the reservoir full.
Normal coolant overflow into recovery bottle is ap-
proximately 1/2 pint (230 ml) during warm-up. The
coolant recovery system draws coolant back into the
reservoir from the recovery bottle as the engine cools.
As long as there is coolant in the recovery bottle, the
reservoir should remain completely full. If not, there's
a vacuum leak, usually at the hose leaving the reser-
voir, or the gasket under the recovery filler cap. The
gasket seals against the outer rim of the filler neck.
IMPORTANT: The coolant (antifreeze) flows
around the outside of the cooling tubes while
seawater flows through the inside of the cooling
tubes in the heat exchanger.
Engine exhaust manifold is seawater cooled. Stern
drive seawater pickup pumps seawater thru the heat
exchanger.
Coolant Recovery Bottle
Before starting engine each day, check to ensure that
coolant is visible in coolant recovery bottle.
If coolant is not visible, check fresh water section of
cooling system (including coolant recovery system)
for leaks and repair, as necessary. Refill fresh water
section with recommended coolant solution, as out-
lined under "Changing Coolant," following.
If coolant is visible, start engine and run until it reach-
es normal operating temperature, then recheck cool-
ant level in coolant recovery bottle. Coolant level
MUST BE between the ADD and FULL marks (on
front of bottle).
! WARNING
Allow engine to cool before removing pressure
cap, as sudden loss of pressure could cause hot
coolant to boil and discharge violently. After en-
gine has cooled, turn cap 1/4 turn to allow any
pressure to escape slowly, then push down and
turn cap all the way off.
If level is low, remove fill cap from coolant recovery
bottle and add required amount of coolant solution.
Use a 50/50 mixture of ethylene glycol antifreeze and
pure, soft water for coolant additions. If frequent addi-
tions of coolant are required, check fresh water sec-
tion for leaks.
CLOSED COOLED MODELS - 6B - 1