Battery Isolator - Mercury MerCruiser Product Applications Manual

Electrical System
• Connect the battery switch into the positive (+) battery cable as close to battery as
possible.
• The switch should be located in a readily accessible location for use in an emergency.
• The switch should never be turned off while the engine is running to avoid damage to
the alternator. Switching between batteries should also be avoided while the engine is
running (unless the switch has been specially designed for this purpose).
• The switch should not be used to connect multiple engines to one battery (or battery
bank). See Multiple EFI Engine Battery Precautions.

Battery Isolator

When designing and installing the electrical system, adhere to all applicable marine
regulations (United States Coast Guard [USCG], European Union–Recreational Craft
Directive [EU-RCD], etc.) and the standards they reference (American Boat and Yacht
Council [ABYC], Society of Automotive Engineers [SAE], International Standards
Organization [ISO], etc.) for the market in which the boat will be sold.
A battery isolator can be installed to allow the charging of an auxiliary battery for use in
operating accessories. The battery isolator will allow the alternator to charge both the
cranking battery and auxiliary battery at the same time, while preventing accessories
connected to the auxiliary battery from discharging the cranking battery. The alternators
used on Mercury MerCruiser products are equipped with a special external sensing circuit
to ensure optimum charging performance in these types of applications (by compensating
for the voltage drop across the isolator).
A special isolator is required for multiple engine installations where the cranking batteries
are to be charged from a common source. See Multiple EFI Engine Battery
Precautions.
The manufacturer's instructions should be carefully followed when making the installation.
Mercury MerCruiser cannot be responsible for problems resulting from installation of the
isolator. The installer and the isolator manufacturer must ensure that the installation and
any modifications to the Mercury MerCruiser product comply with all applicable standards
and regulations, including (but not limited to) wire size, type, routing, terminals, and
overcurrent protection.
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WARNING
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CAUTION
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90-863758060 AUGUST 2006