Multiple Efi Engine Battery Precautions; Flame Arrestor - Mercury 6.2L MPI Manual

Section 4 - Maintenance
Connect electrical components such as LVDs (low voltage disconnects), VSRs (voltage sensing relays), and ACRs (automatic
closing relays) to an isolated auxiliary battery bank.
Review ABYC regulations for power connection points.

Multiple EFI Engine Battery Precautions

Alternators: Alternators are designed to charge the battery that supplies electrical power to the engine that the alternator is
mounted on.
EFI propulsion control module (PCM): The PCM requires a stable voltage source. During multiple engine operation, an
onboard electrical device may cause a sudden drain of voltage at the engine's battery. The voltage may go below the PCM's
minimum required voltage. Also, the alternator on the other engine may now start charging. This could cause a voltage spike in
the engine's electrical system.
In either case, the PCM could shut off. When the voltage returns to the range that the PCM requires, the PCM will reset itself,
and the engine will operate normally. The PCM shuts off and resets itself so quickly that the engine may only seem to have an
ignition miss.
Batteries: Boats with multiengine EFI power packages require each engine be connected to its own battery. This ensures that
the engine's PCM has a stable voltage source.
Battery switches: Battery switches should always be positioned so each engine is operating off of its own battery. Do not
operate engines with switches in both or all position. In an emergency, another engine's battery can be used to start an engine
with a dead battery.
Battery isolators: Isolators can be used to charge an auxiliary battery used for powering accessories in the boat. They should
not be used to charge the battery of another engine in the boat unless the type of isolator is specifically designed for this
purpose.
Generators: The generator's battery should be considered another engine's battery.

Flame Arrestor

Fuel is flammable and explosive. Ensure that the key switch is off and the lanyard is positioned so that the engine cannot
start. Do not smoke or allow sources of spark or open flame in the area while servicing. Keep the work area well ventilated
and avoid prolonged exposure to vapors. Always check for leaks before attempting to start the engine, and wipe up any
spilled fuel immediately.
1. There are two engine covers you must remove to access the flame arrestor:
a. Pull the outside engine cover up to remove it from the four rubber mount grommets.
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