Yanmar Marine Alternator Belt Fault / Battery Light
The YANMAR-ALTERNATOR-BELT (Yanmar) diesel fault code means: Yanmar Marine Alternator Belt Fault / Battery Light. This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- beginner
- Estimated cost
- $30-$500
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Common Symptoms
- Battery lamp on at helm
- No charging voltage
Probable Causes (Ranked by Likelihood)
- Stretched / glazed alternator belt Very Likely
- Seized seawater pump causing belt squeal Likely
- Failed alternator Possible
Step-by-Step Diagnostic Procedure
Check belt tension and condition.
Rotate seawater pump shaft by hand -- should turn freely.
Test alternator output at battery.
Frequently Asked Questions
What is Yanmar code MARINE-BELT?
Yanmar MARINE-BELT: Yanmar Marine Alternator Belt Fault / Battery Light. This code is reported on Yanmar equipment running the described engine family.
Can I keep working with Yanmar code MARINE-BELT?
Limited operation only -- finish the current task then shut down for repair.
How much does Yanmar MARINE-BELT cost to fix?
Typical repair cost: $30-$500. Off-road diesel shop labor runs $125-$175/hr in 2026. Dealer diagnostic software (Yanmar SmartAssist / YDT) is usually required.