Battery; Multiple Efi Engine Battery Precautions - Mercury Mercruiser Tow Sport 5.7 MPI Manual

Section 5 - Maintenance
b. All other models: Using appropriate connector, connect the flushing hose from the water to the water inlet hose
(upper hose) of the seawater pickup pump. Proceed to Step 3.
3. Open the water source completely.
4. Place remote control in neutral, idle speed position, and start engine. Operate engine at idle speed, in neutral, for about 10
minutes or until discharge water is clear.
5. Stop the engine.
6. Remove the flushing connector from the water inlet.
7. Reconnect the water inlet hose.
8. Tighten hose clamp securely.
9. Attach to the next engine, if equipped, and repeat procedure.
10. Turn off the water source.
11. Open the seacock, if equipped, or unplug and reconnect the water inlet hose prior to operating the engine.
NOTE: If the unit is to be stored in the water, the seacock should remain closed until time of usage. If unit is to be stored
out of the water, open the seacock.
12. Replace the propeller if removed. Refer to the boat manufacturers' instructions.

Battery

Refer to specific instructions and warnings accompanying your battery. If this information is not available, observe the following
precautions when handling a battery.
Recharging a weak battery in the boat, or using jumper cables and a booster battery to start the engine, can cause serious
injury or product damage from fire or explosion. Remove the battery from the boat and recharge in a ventilated area away
from sparks or flames.
An operating or charging battery produces gas that can ignite and explode, spraying out sulfuric acid, which can cause
severe burns. Ventilate the area around the battery and wear protective equipment when handling or servicing batteries.

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. When batteries for two different engines are connected, one alternator will supply all of the charging current for
both batteries. Normally, the other engine's alternator will not be required to supply any charging current.
EFI electronic control module (ECM): The ECM 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 ECMs
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 ECM could shut off. When the voltage returns to the range that the ECM requires, the ECM will reset itself,
and the engine will operate normally. The ECM shuts off and resets itself so quickly that the engine may only seem to have an
ignition miss.
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