Offshoreonly.com - 350 Mag Bravo III overheat high RPM only

Last year I dragged my crownline 290cr through the mud at 42mph in the hudson river.

Port Engine started to overheat at all RPM's I limped the boat into Kingston and changed the impeller. It then over heated at cruising RPM's.

I then limped the boat back to CT (120 miles) and flushed the system out. I have closed water cooling on the block only( not the exhaust manifolds). Reversed flushed the fuel cooler, through the transmission cooler. Cleaned the heat exchanger There was seaweed clogging the heat exchanger.

Worked well for a couple engine hours.... Now I am back to overheating at high RPM's.....

I am thinking that my gimbal hose is collapsing or that the insides of the intake hose is collapsing (it has wiring embedded)....

Replacing the gimbal hose is a PITA any thoughts or possibilities on testing or other possible problems before I take this monster out of the water and pull the drive??