Thanks is this all great stuff.

I think I will pull the system back down again and check everything again. I know I ran a coat hanger through all the passages in the exchanger and the oil cooler, ( power steering was pretty much open). Only thing I did not check but put my finger in were the risers. I just ordered new gaskets and will pull the risers and inspect them.

Hello again. I did the flowing so far and here are the results
I replaced all the hoses, pulled the oil cooler and power steering cooler inspect and cleaned. These items were all clean. I pulled the risers since this is the only thing in the raw water system. Riser were perfect, and clean. I removed the heat exchanger and this was clean as well. I also pulled sea pump and put in new impeller and wear plate.

So from the transom to the exhaust it is all new and inspected.

My issue now is boat starts fine, idle fine, temp at 160 but when running at 3000 rpm temp starts to climb to 180. I'm sure the boat use to run at 160 before. When I slow down or stop the temp returns to 160 / 170 ish depending how long I wait.

I took it out for the day and it seems to hold at 180.

The only other place that I have not removed and inspected was the outdrive.
The out drive is a bravo 3 and this is where the pick up is. I back flushed the out drive and water comes out fine. I have read that the hose in the out drive could collapse when under suction, is this possible?

Any suggestions comments ?
Should remove the outdrive?

Had the same issue with a boat a few years back. Ran at the perfect temp until engine RPM was above 4k. Turns out debris and a small piece of an impeller blade was blocking the heat exchanger not allowing enough water flow through the engine at higher rpms. Never had an issue after that.

I'm having similar issue. When I get time I'm going to replace the one manifold that's getting hot. Maybe it's clogged in there... Water seems to be flowing good everywhere else

Sorry I should have updated this thread. I found the issue. It was the raw water hose in the drive that leads up to the transom. Apparently, this is a common issue, was not a bad fix but now everything there is new.

Was the hose cracked? If so, it would make sense that once you get up on plane, the hose would start sucking air and compromise the amount of water that it was drawing from the outdrive.

No actually it was corrosion on the hose which collapsed the threaded insert in the gimbel housing area. I removed the hose and installed 2 new inserts (for either side of the hose) and was back in business.