Yes,I also back flushed and cleaned the heat exchanger,I’m baffled.The only thing left to do is pull the outdrive and look for any pinched or blocked hose.
So I i replaced the housing unit and impeller on my 496 mag engine and pulled off the blue plug on the side to verify that water was going into the housing unit itself,I noticed that while the outdrive was up I had plenty of water going through but as soon as I dropped the outdrive very little...