8.1Gi-CE exhaust overheat warning

[Xman214]

Good morning,

I reposted this from the general forum.

I recently had my serpentine belt shred itself to almost bits but was able to get the remainder of the belt back on and limp home. Indications were lost power steering and then the engine overheat warnings came on. So once back in port I took the boat out of the water and replaced the serpentine belt and impeller. Trailer fired the engine and everything worked fine. Then I put the boat back in the water and in the short transit to the slip the exhaust overheat warning came on as did the engine overheat. Serpentine belt was still attached so after everything cooled I decided to look at the impeller and see if it was defective which it was not. I noticed the threaded side was facing out so I turned it around and closed everything back up. Started engine and cooling system works fine now....never though that the impeller could be installed incorrectly but I was able to pull it off.

So the main issue - shortly thereafter the engine exhaust overheat warning came on which caused the motor to go into a safe mode limiting rpm. At this point I have no idea what I could have done to cause this other than a bad transmitter or potentially air in the cooling system. I checked all the wiring and everything looked attached. Any assistance would be appreciated!

Xman214

[Xman214]

Fixed it!

[AsLan7]

Fixed it!

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I see there were crickets in this post Xman. Sorry to see it got buried...but happy to see you fixed it.

Any words of wisdom or was it straightforward?
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[Xman214]

Thanks for noticing! I received all kinds of advice from boat mechanics and old timers but new sensors, clogged hoses etc were not the problem. So I used a laser heat sensor to determine where the hot spot was and just followed the path checking each component in the sequence. It turned out to be a flow control valve that is the last component before coolant reaches exhaust cooling manifold. I took it apart and the valve and thermatic pin were just laying disassembled inside of housing. They were caked in scale. I took apart the opposite side also and it was correctly assembled with just a little scale buildup. It appears that the component might have been defective from the original install and finally caked up with scale from irregular flow pattern blocking all coolant flow. I thoroughly cleaned both flow valves and temperatures are now in 130s vice 210+.

Feel somewhat vindicated!

Xman214

[Big Block Power]

That's cool. Great find. Did you take any pictures and where it is located for future 8.1 guys.