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Port Exhaust overheating on my 28QX with 8.2 l IO

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sjshoes

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Im getting an alarm on console showing system error. Engine has new impeller and shows perfect water pressure and is running very cool in normal range. It has a closed coolant system. When checking with a code reader is shows my Port exhaust is overheating when at 3000 rpm and above. It goes into reduced power mode untin cooling down. Rund pretty normal at lower setting but still shows a 30 degree difference in port and starboard headers. What is possible solution?
 
Thanks for reply. It has new water pump and engine runs very cool and well within specs at all rpms.. only fault is the port exhaust manifold goring over temp at mid rpm. Cooks right back down when back at idle. Starboard side right on spec at all rpms.
 
Good thoughts. We’ve also used laser temp gun and confirms code reader software almost to the degree. I believe the laser gun to be more reliable. . Problem exists still. Engine is in a Bennington 28QX pontoon
 
Always fresh water. It has a closed coolant system. Raw water system has new pump, thermostat and has been flushed including the oil cooler. Problem is on the freshwater system once past the heat exchanger.
 
No, as previously mentioned… port side runs cool as starboard side at idle. It rapidly increases temp at 3k and above to a point the guardian system kicks in and brings power back down. Once both sides temps return to normal range at idl, we can reproduce same issue by bringing rpms back up. Then port again repeats issue.
 
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Have you checked the temp with temp gun on the water hoses going into the manifold? According to the diagram I looked at, there are 3 hoses going to each manifold. One is for closed cooling water into the manifold, one for closed cooling water exiting the manifold and one is for seawater to enter the manifold to exit out the exhaust.
 
Check for a splitter or diverter in either the closed or sea water system that is plugged or not operating. Also, the ports that dump sea water into the exhaust flow are rather small and subject to debris restrictions. Check downstream of that exhaust cooling point for high temp versus the other side.

Before pulling any exhaust manifold, confirm that flow of raw water to the manifold is good (sounds like you have checked the flow of closed system coolant is good?).

As an aside, with the new water pump/system flush, be sure all hoses were reconnected correctly. Even a kinked hose for the manifold coolant exit could be the problem. Might there have been a thermostat replacement that is not EXACTLY the correct model?
 
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