Coolant Temperature High Shutdown Triggered

Common Symptoms

• Engine shuts down suddenly at cruise or under load and will not restart until it cools
• Instrument cluster or EVC display shows SPN 110 FMI 0 or a high-temp warning before shutdown
• Coolant temperature gauge climbs into the red zone before the shutdown event
• Raw-water exhaust discharge noticeably reduced or completely stopped at the transom
• Exhaust smoke smells burnt or shows steam from overheated coolant
• Engine restart attempts immediately after shutdown are blocked by the ECU until temp drops
• Alarm horn sounds continuously on the helm panel before or during the overtemp event

Probable Causes (Ranked by Likelihood)

• Failed or worn raw-water impeller not moving enough sea water through the heat exchanger Very Likely
• Sea-water intake strainer clogged with weed, debris, or barnacle growth restricting flow Very Likely
• Thermostat stuck closed preventing coolant circulation in the closed loop Likely
• Heat exchanger tubes fouled with scale, salt, or marine growth reducing heat transfer Likely
• Coolant level low due to slow leak at hose, clamp, heat exchanger end cap, or coolant pump seal Possible
• Raw-water pump housing or impeller cover cracked, causing air ingestion and loss of prime Possible
• Coolant temperature sensor sending an incorrect high reading to the ECM (false shutdown) Less Likely

Step-by-Step Diagnostic Procedure

1. Let the engine cool completely before touching anything. Removing a pressure cap on a hot system causes severe burns. Wait at least 30 minutes after shutdown.

2. Check the raw-water strainer at the sea cock. Remove the basket and inspect for weed, shells, or debris. Rinse it clean and reinstall before any further steps.

3. Verify sea cock is fully open. It sounds obvious but a partially closed sea cock is a common cause after winter layup or recent haulout.

4. With the engine cool, inspect raw-water discharge at the exhaust or transom. Start the engine briefly and confirm a steady stream of water is flowing out. A trickle or no flow points directly to impeller failure or blockage.

5. Remove the raw-water impeller cover (typically 4-6 bolts on the pump body mounted to the engine). Pull the impeller and inspect for missing, cracked, or deformed vanes. A healthy impeller has firm, unbroken vanes. Replace if any vane is cracked or missing, or if the last replacement is more than 2 seasons ago.

6. Check closed-loop coolant level at the expansion tank with the engine cold. The level should be at the MAX mark. If low, top up with the correct Volvo Penta pre-mixed coolant and inspect hoses and clamps for wetness or staining that indicates a slow leak.

7. Inspect all coolant hoses (both raw-water and fresh-water sides) for soft spots, cracking, or collapsed sections that could restrict flow. Squeeze each hose firmly. It should feel firm and spring back, not collapse.

8. If raw-water flow is good and coolant level is correct but the engine still overheats, the fault likely lies with the thermostat or heat exchanger fouling. Testing the thermostat requires removal and a hot-water bench test. Heat exchanger inspection and back-flushing requires a technician with the appropriate flush kit. Use the Volvo Penta VODIA diagnostic tool via the EVC system bus to verify whether the coolant temperature sensor reading matches an independent infrared thermometer reading on the engine block. If the sensor reads high while the block feels normal, the sensor itself may be faulty.

Frequently Asked Questions