2008 Johnson 150 FICH Overheat

Im working on a 2008 Johnson 150 FICH, which is the port motor of twins. The engine runs greats, starts well, has solid compression. It was having a overheat problem at @3300 RPM under load. Replaced both thermostat/pressure release valves on each bank. Replaced the impeller. Ran a dose of Salt Away through it as well according to the instructions. The boat now still runs fine but overheats at @3800 RPM under load. The starboard engine is not overheating and runs well. What am I overlooking? Didn't find excessive corrosion or sand under the thermostats or in the water pump. The old impeller looked ok but had taken a set as most do over time. Boat is back in the water again so it is difficult to drop the lower unit again.

If it was my motor I'd get a cheap temp gun and verify it was over heating and not some weird electrical problem.

What are you overlooking?

What am I overlooking should be the question.

I cannot find any 2008 Johnsons at all, nor any 150 Fichts. 2006 Johnson 150s were carbed.

So what am I overlooking?

Me either......anyway the later models have a remote mounted poppet so you need to check the spring and diaphragm in it.

The fitting which goes from the head to drain on the starboard bank was cracked at its base. Replaced the head, added new o rings and after a water test it is running fine now and not a sign of an overheat. Thanks everyone

do you have a pic of this fitting?

Sorry no picture of the fitting. It was a space age polymer (plastic) 90 degree fitting threaded into center of starboard head of the port engine. Hose nipple on other end of fitting.