Engine ran at 200 degrees/ need to diagnos over heating.

[adam mouas]

I have a sea ray 380 sundancer. Powered by dual 8.1l mercruiser v drives.
Yesterday the port engine started running at 200 degrees and shut off. I believe I can change the impeller but was wondering how to diagnos a bad heat exchanger. I had steam coming out the exhaust so I figured it might but something more than an impeller?
Anyone have any thoughts.

 

[Jimmy Buoy]

Steam coming from the exhaust (if not a normal thing for your boat) is a sign of hotter than average engine cooling water. On the 8.1's the typical issue can often be raw water pumps that are no longer pumping with adequate pressure (due to impeller condition or wear within the pump housing) or blockages within the exhaust manifolds from corrosion. either way, the cooling sea water flow is probably being impaired to the point where it can no longer provide enough cooling for the engine. The other less probable issue may be the engine's recirculation pump failing but that should be evident with coolant leaking out the weeping hole (the pump is run via a pulley on the front of the engine).

 

[adam mouas]

It was impeller. Thanks for the response.