Looks to me like you're still dealing with contaminated fuel/dirty carburetor problems. In your post I did not see where you:
- disassembled and thoroughly cleaned the carburetor
- cleaned the fuel tank interior
- determined the source of the water incursion in the tank and repaired so it never happens again
- discarded the questionable fuel and refilled with fresh
The water flow out the exhaust looks normal to me considering the low RPM in the video but there's certainly no harm in replacing the impeller anyway. Is there any real indication of overheating beyond your theory? What is the history of this engine?