This is what i do when my 4236 start to geting hot, about 210 at hig rpm
1, raw water pump
coolers and heat exchanger
3, header tank cleaning, lots of scale inside.
6.check if the fresh water pump impeller is working and check for leaks
. in this case nothing to do with the fresh water pump, works ok.
7. flush and clean all the water pasages in the engine
block, there is some drain plugs somewhere,
8. elbow. check for carbon scale and corrosion
9. finally top the dam thing with a good antifreeze
mix and run the engine
Now the engine stuck in between 170 and 180 no matter the rpms, full rpms same, 180.
Hope this help.