Mercury 8.1S Horizon, Product Applications Manual

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Cooling System
Page 7A-2 90-863758060 AUGUST 2006
Lubricant, Sealant, Adhesives
Tube Ref No. Description Where Used Part No.
9
Loctite 567 PST Pipe Sealant Hose fitting threads and plastic plug threads 92-809822
116
RTV 587 Ultra Blue Silicone Sealer Sealing surfaces and screw shaft 92-809825
Special Tools
Computer Diagnostic System (CDS) Order through SPX
4520
Monitors all electrical systems for proper function, diagnostics,
and calibration purposes. For additional information, pricing, or
to order the Computer Diagnostic System contact:
SPX Corporation
28635 Mound Rd.
Warren, MI 48092
or call:
USA - 1-800-345-2233
Canada - 800-345-2233
Europe - 49 6182 959 149
Australia - (03) 9544-6222
General Information
Mercury MerCruiser engines have either a seawater cooling system or a closed cooling
system. Seawater cooling systems are sometimes called raw water cooling or standard
cooling, while closed cooling systems are sometimes called fresh water cooling. On
engines with seawater cooling, the engine is cooled entirely by the seawater in which the
boat is being operated. Closed cooling systems use a combination of fresh water
(antifreeze and water) and seawater for cooling. Both types of systems are designed to
keep the engine operating temperature at approximately 71 degrees C (160 degrees F)
for optimum performance, fuel economy and durability. (Refer to cooling system flow
diagrams at end of section.)
To monitor the cooling system, a temperature switch is incorporated into the audio warning
system, which alerts the operator of an abnormal condition if the temperature exceeds
approximately 93 degrees C (200 degrees F). A temperature sender is also employed to
operate a temperature gauge at the dash. On dual helm applications, this sender must be
replaced with a dual station sender to obtain the proper temperature reading at both
stations. Refer to the
Instrumentation and Controls section for more information.
The cooling system must receive a sufficient amount of seawater under all operating
conditions to operate properly. The design and installation of the seawater supply system
is the boat manufacturer's responsibility. Cooling system components must be constructed,
sized, and installed in accordance with the following guidelines.
!
CAUTION
Do not operate engine without water flowing through the seawater pickup pump, damage
to the pump impeller and subsequent overheating damage to the engine or sterndrive
unit may result.