Troubleshooting; Before You Begin; Charging Output Tests - Mercury MerCruiser Service Manual

Charging System
2. Remove the belt from the idler pulley and slowly relieve the tension on the breaker bar.
a
3. Inspect the belt for damage and replace as necessary.
4. Route the belt according to the diagram on the decal.
5. Carefully release the tensioner and ensure that the belt stays positioned properly.
6. Check the belt tension.
NOTE: Proper tension is a measurement of deflection with moderate thumb pressure on the belt at the location that has
the longest distance between two pulleys.
Description
Deflection

Troubleshooting

Before You Begin

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.
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.
IMPORTANT: The charging system may be damaged by:
• Reversed battery cables
• Running the engine with the battery cables disconnected
• An open circuit, such as a broken wire or loose connection
Before proceeding with the tests in this section, perform the following checks to eliminate possible problem areas.
1. Check the charge and physical condition of the battery and battery cables. The battery must be at least 75 percent (1.230
specific gravity) charged to obtain valid test results. Ensure that the battery is fully charged before testing the system.
NOTE: An undercharged battery can result from excessive current draw from excessive accessory power loads or by
extended operation at low speeds.
2. Inspect the charging system wiring for damage or corrosion. Ensure that all connections are secure and clean.
3. Check the alternator drive belt for proper tension, excessive wear, cracks, fraying or glazed surfaces. Replace if necessary.

Charging Output Tests

1. Check the drive belt condition and tension.
2. Check battery charge and condition.
3. Connect the digital multi‑tester (DMT) leads directly to the battery posts.
Page 4C-10
Standard cooling shown, closed cooling similar
a - Belt tensioner
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WARNING
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WARNING
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© 2016 Mercury Marine
13 mm (½ in.)
90-8M0099748 eng DECEMBER 2015