2019 Nautique 200 6.0 Overheating Issue

[kennethgallo]

Hello,
We have a 2019 Nautique 200 equipped with a 6.0-liter engine, and we're encountering engine cooling temperature codes DTC 116, 1415, and 1416.

We've already replaced the impeller and pump, reverse flushed the strainer, transmission cooler, and oil cooler, and tested and replaced the thermostat. During a pass, the engine temperature rises above 200°F, but it cools down at the end of the lake, indicating that the thermostat is functioning. When we remove the thermostat, the boat runs cold, but it doesn't produce enough power in this mode. The engine maintains temperature when city water is fed into the inlet, effectively forcing more water through the engine.

Has anyone experienced a similar issue?

[NautiqueJeff]

Yes. Pull the end caps off of the heat exchanger. I bet you find old impeller pieces blocking the water flow.

[behindpropellers]

There is another thermostat above on top of the engine to keep the manifolds warm, might want to check that.

[mlange]

The following is from the PCM Diagnostic Service manual for a 1415/1416:

If the “EMWT1 High Voltage” fault is also present, follow the troubleshooting procedures for that fault as it may have caused “EMWT1 Sensor Higher Than Expected 1.”

□ Check that the heat exchanger has a proper amount of ethylene glycol/water and that the heat exchanger is not leaking

□ Ensure that there is no trapped air in the cooling path

□ Inspect the cooling system for cracks and ensure connections are leak free

□ Check that the raw water pickup is not blocked/restricted by debris and that the hose is tightly connected

□ Check that the thermostat is not stuck closed

□ Check that the raw water pump/impeller is tact and that it is not restricted

□ Verify that the proper amount of raw water fl ow is being achieved, both static and underway