Weird overheating issues

[Backyardmech]

I have a 2001 vp 5.0gl. It recently overheated due to bad impeller and raw water pump. After replacing the raw water pump and while running on the internal water hose directly to the raw water pump the water flow through the exhaust would stop and all the water would divert through the lower water intake ports in the out drive. Significant water was in cylinder 3 so I pulled the heads and one head gasket was blown. I took that head to the machine shop and they found that it was cracked. I replcace the head with a one rebuilt by the machine shop. After installing that head with new gaskets and thermostat everything seemed fine. Water flow out of the exhaust was good at idle and medium rpm. After doing several cycles medium rpm for a few minutes and idle with the temp fluctuating between 150 and 165 I let the engine at idle for about 20 minutes while I was looking for hose leaks and listening for odd sounds. While poking around a hose felt too hot and the temp guage read 200°. I shut down immediately.

Tldr.
What could cause the temp to spike after idling for 20 min after being cycled between med rpm and idle for about 30 min with no overheating issues? All on internal fresh water hose directly to to raw water pump.

 

[Lou C]

Did you have the head on the opposite side checked for cracks?