'88 390EC Overheating

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I hope I am in the right place. Ok, 1988 390EC340 wo Closed Cooling is overheating. Originally, was at idle and heard the port side exhaust note change. Shortly after, it starts overheating and had to shut down. I began by replacing the impeller (nothing bad with old one). I have run water from the starboard inlet to the port motor, still overheats. Pulled each section of hose off and I am getting good water through every section. I have back flushed the trans and oil coolers. I am blowing steam, so I know it's not the gauge. I am down to 3 things. Risers, head gasket, or Circulation pump. I have not puller the risers, but I am not sure what to look for or ways to test these things....anyone?

 

[electricaldoctor]

Plz check "Official 390 EC Thread"

 

[hottoddie]

If you do not have a history on the boat then you need to start from scratch. An infrared thermometer is a big help to locate hot spots and narrow down the problem. Many things can cause an engine to overheat.

 

[scoflaw]

Risers are a good place to start, your looking for rust clogging the water passages. Your heat exchanger could be plugged up as well.

 

[Saverio]

Since your raw water cooled I would also check your t-stats. Mine are 140. But I'm fwc. +1 on the heat temperature gun. Compare riser temperatures