Yanmar Marine Low Coolant Alarm
The YANMAR-LOW-COOLANT (Yanmar) diesel fault code means: Yanmar Marine Low Coolant Alarm. This is a serious severity code.
- Keep driving?
- Limited driving only
- DIY difficulty
- beginner
- Estimated cost
- $25-$600
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Common Symptoms
- Low coolant lamp / buzzer
Probable Causes (Ranked by Likelihood)
- Leak at heat exchanger end cap O-ring Likely
- Leaking coolant hose Likely
- Cracked expansion tank on older YM series Possible
Frequently Asked Questions
What is Yanmar code MARINE-LOW-COOLANT?
Yanmar MARINE-LOW-COOLANT: Yanmar Marine Low Coolant Alarm. This code is reported on Yanmar equipment running the described engine family.
Can I keep working with Yanmar code MARINE-LOW-COOLANT?
Limited operation only -- finish the current task then shut down for repair.
How much does Yanmar MARINE-LOW-COOLANT cost to fix?
Estimated repair cost: $25-$600. Off-road diesel shop labor runs $125-$175/hr in 2026. Dealer diagnostic software (Yanmar SmartAssist / YDT) is usually required.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
Pressure-test cooling system to locate leak.
Inspect heat exchanger end caps for seep stains.
Top off with Yanmar-approved ethylene glycol.
Commonly Affected Vehicles
- Hunter / Beneteau / Catalina sailboats with Yanmar 3JH / 4JH
- Trawlers and sport fishing boats with Yanmar 6LY / 6LF series
- Sailboat auxiliaries with Yanmar 2YM / 3YM / 3JH5 diesels
- Commercial fishing vessels with Yanmar 6LY3-UTP
- Yachts with Yanmar 6LY400 / 6LY440 / 8LV common-rail marine diesels
- Workboats with Yanmar 4LV / 4JH series marine propulsion
- Ski boats and express cruisers with Yanmar marine diesels
- Tenders and RIBs with Yanmar 3YM20 / 3YM30 sailboat aux
- Island-hopper ferries with Yanmar 6AYM / 6HYM commercial series
- Tug boats and small workboats with Yanmar 6HAL-HTP / 6HYM
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