Overheating with closed cooling system???

[KEVIN D TOBIN]

Getting an occasional "overtemp" fault on smartcraft. Port motor Goes into guardian mode.
I have a closed system. Just changed the raw water impeller today. The old one looked fine.
Not sure of next steps. Mechanics are booked out up here.

Any suggestions?

replace return hose with clear hose to see flow, use laser temp gauge to check risers and other points, these are all low cost methods, you can get everything you need at lowes, fwc systems are tricky to trouble shoot, take one thing at a time, good luck, do you have a strainer between your raw water pump and your exchanger ? just in case the pump impellar breaks down.