Mercury MR504LB3 Manual page 80

Section 5 - Maintenance
Engine Control Module (ECM) and Vessel Integration Panel (VIP). The ECM and VIP require 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 drop below the ECM or VIP minimum voltage requirements. The alternator on the second engine may also start
charging, causing a voltage spike in the engine's electrical system.
In either case, the ECM could shut off. When the voltage returns to the range that the ECM requires, the ECM will reset itself.
The engine will now run normally. This ECM shut down usually happens so fast that the engine just appears to have an ignition
miss. Intermittent or temporary VIP shutdown can cause a loss of instrumentation, engine misfire and can adversely effect
power package performance and boat safety.
Batteries. Boats with multi‑engine electronic control power packages require each engine be connected to its own battery,
ensuring that the engine's ECM has a stable voltage source.
Battery Switches. Battery switches should always be positioned so that each engine is operating off of its own battery. Do not
operate engines with switches in the 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.
Page 72 90-8M0089579 MARCH 2014
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