The BF 225 will overheat on muffs normally unless you have exceptional water pressure, which most don't have. You need to test it in a barrel filled with fresh water and the water constantly being refreshed. Otherwise, it will quickly heat up. Remove prop first.
Yes, change out the impeller and observe whether or not any pieces are missing. Usually it's best in these situations to change out the whole water pump because an overheat will often warp the pump liner - that is, the piece that the impeller fins ride against. The difference between an impeller kit and the water pump kit is about $80 on boats.net.
See:
https://www.boats.net/catalog/honda...25hp/bf225a6-xca-2006/water-pump-impeller-set
Pull fault codes. Then clear them. Then test the engine again. The procedure for getting and clearing fault codes is attached.
View attachment Procedure for Getting Fault Codes.pdf
What the fault codes mean is attached.
View attachment MIL fault codes.pdf
Let us know what codes you get before clearing them. Then let us know what codes you get after you run the engine and get an alarm.
Typically in an overheat situation, if the t-stats stick, they will get stuck open, so normally the engine would be running too cool. No alarm for that. However, if you are running in saltwater, it's always a good idea to remove the t-stats, clean them, clean out any corrosion under the seats, and reinstall with new O rings.