Mercury 8.1S Horizon, Product Applications Manual

Page: 121 / 163

Electrical System
Page 8A-2 90-863758060 AUGUST 2006
Lubricant, Sealant, Adhesives
Tube Ref No. Description Where Used Part No.
Battery connection sealant Battery terminals Obtain Locally
25
Liquid Neoprene
Engine cable connections
All electrical connections
92-25711-3
Finding Other Diagrams
NOTICE
Refer to the appropriate Mercury MerCruiser Diagram Binder for wiring diagrams or other diagrams not found
in this manual.
General Information
This section covers the engine portion of the electrical system. For instrumentation related
information, see
Section 9 .
The electrical system is a 12-volt, negative ground system. High output (65/72 amp)
alternators are included as standard equipment. Their high output design helps ensure that
the battery remains fully charged for trouble-free starting, while providing extra capacity to
handle the accessories used on today's boats. All alternators are equipped with an external
sensing circuit to maintain the battery at the optimum voltage level, while providing for the
use of a battery isolator, if desired. Special high-capacity marine starters are also employed
to provide reliable starting and long life in the rigorous marine environment. Mercury
MerCruiser starters, alternators, distributors, solenoids, circuit breakers, fuses, and other
components that could generate a spark comply with external ignition standards and
regulations to prevent the ignition of combustible fumes in the engine compartment should
they exist. These components should not be confused with standard automotive
components, which typically do not have this provision. The electrical system is equipped
with numerous overcurrent protection devices (circuit breakers, fuses) to protect the engine
against shorts and overloads. See
Wiring Diagrams for the location of these devices. The
engine compartment should be designed to allow access to these components.
IMPORTANT: No one component is more important in ensuring the reliability of the
electrical system than is the battery and related hardware. The installation of the battery
and cables is the responsibility of the boat manufacturer. The guidelines outlined in this
section must be carefully followed when selecting and installing these items.
Precautions
!
WARNING
Electrical, ignition, and fuel system components on Mercury MerCruiser engines and
sterndrives are designed and manufactured to comply with U.S. Coast Guard rules and
regulations to minimize risks of fire or explosion.
The use of replacement electrical, ignition, or fuel system components that do not comply
with these rules and regulations could result in a fire or explosion hazard and should be
avoided.
When servicing the electrical, ignition, and fuel systems, it is extremely important that all
components be properly installed and tightened. Otherwise, any opening in the electrical
or ignition system would permit sparks to ignite fuel vapors from leaks in the fuel system,
if they existed.