76839 Mercruiser MOUNT, FRONT SUPORT

Recommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.
Table 1
Troubleshooting Test Steps Values Results
1. Condition of the Alternator Drive Belts
A. Inspect the condition of the alternator drive belts.
B. Check the belt tension. If the engine is equipped with an automatic belt tensioner, check the automatic belt tensioner.
Excessive belt tension can result in damage to the alternator.
Drive belt
Result: The alternator drive belts are in good condition and the belt tension is correct.
Proceed to Test Step 2.
Result: The alternator drive belts are not in good condition or the belt tension is incorrect.
Repair: If the alternator drive belts are worn or damaged, replace the belts. Refer to Disassembly and Assembly for the correct procedure.
If necessary, replace the automatic belt tensioner. Refer to Disassembly and Assembly for the correct procedure.
If the problem is not resolved, proceed to Test Step 2.
2. Condition of the Alternator Drive Pulley
A. Check the condition of the alternator drive pulley. Look for deep grooves that have been worn into the pulley by the belt. Check that the nut for the pulley has not become loose.
Alternator drive pulley
Result: There is excessive wear on the alternator drive pulley.
Repair: Replace the pulley.
Result: The alternator drive pulley nut was loose.
Repair: Tighten the nut.
Result: There is not excessive wear on the alternator drive pulley.
Proceed to Test Step 3.
3. Wear of the Alternator Bearings
A. Check the alternator bearings for signs of wear.
Alternator bearings
Result: The alternator bearings are OK.
Proceed to Test Step 4.
Result: The alternator bearings are not OK.
Repair: Repair the alternator or replace the alternator, as needed. Refer to Disassembly and Assembly for the correct procedure.
If the problem is not resolved, proceed to Test Step 4.
4. Inspect the Cables, Wiring, and Connections
A. Inspect the battery cables, engine ground, and wiring. Clean and/or wire brush connections if needed.
Wiring circuit
Result: The wiring circuits are OK.
Proceed to Test Step 5.
Result: The wiring circuits are NOT OK.
Repair: Repair any issues that are found with the wiring circuit.
If the problem is not resolved, proceed to Test Step 5.
5. Check the Signal Wire at the Alternator
A. Turn the keyswitch to ON.
B. Check the signal wire on the alternator for 12 V by touching the positive lead of the multimeter to the signal wire on alternator (CWL: 111-YL, MHE: 123- WH) and the negative lead to any frame ground.
Signal voltage
Result: The voltage is OK.
Proceed to Test Step 6.
Result: The voltage is NOT OK.
Repair: There is a problem with the wiring from the fuse block to the alternator. Repair any issues that are found.
6. Check the Alternator for Proper Operation
A. Draw down the battery to below 12.4 V by turning on the lights or other loads for approximately 5 minutes. Start the machine.
B. Check the amperage of the alternator cable. The amperage will vary based on functions turned on in the cab. It is between 20A to 40A.
Note: As battery charge increases, the alternator amperage output will decrease.
C. Check the voltage at the battery positive post. After 10 minutes of operation it should be 14V 0.5V.
Alternator
Result: The alternator is NOT OK.
Repair: Replace the alternator.
Result: The alternator is OK.
Repair: Refer to Testing and Adjusting, Battery - Test.