What should my 2006 350 mag be running for cooling temps on average?

165-170* on the gauge

I m running 160-180

158 to 170

scan tool is best to monitor temps thru out all rpms

Gen VII water pump impeller and its housing that get internally scored are the cause if in fact you have higher temps.

Next question is this a closed cooled app ? cause they run a bit warmer and is this a saltwater boat ever ???

also 14 year old engine has the t stat been change - 10 years max on t stats for raw water cooled that have been in NO saltwater ever . Salt water apps 2 to 5 years.

Just replaced both impellers with quick silvers. Brass housing wear surfaces had a slight waviness to them. Had the boat out 3 times last fall. From what I remember it always ran 170. Now it was almost up to 200 the other day on lake Michigan after rebuilding the pumps.
Seems the more I ran it the lower the temps got. Then it ran consistently 160 to 180. 180 when on plane and 160 to 170 idling around.
I just acquired the boat last fall and went over some specifics with the dealer who had been maintaining it. I think thermostats were replaced but not 100% sure. Its a freshwater boat and not a closed cooling system.

The gauge could be off some. They have 160* T stats in them. Verify with a scan tool as BUP said.
I believe the high temp alarm sounds at 195-200*