2015 PCM ZR409 - Exhaust Manifolds - Overheating

[scotchipman1 0]

My 2015 ZR409 exhaust manifolds are overheating then my boat goes into some kind of limp mode. My ZR409 has coolant in the engine block and fresh water in the manifolds with a heat exchanger in the rear. No engine light is coming on and the water temp is reading normal. What I think is happening is the exhaust manifolds are getting clogged up? When I pull the plugs on the manifolds I get a lot of debris coming out with the water that looks like silt or hard water that has been baked onto the inside of the manifold then has flaked off. This is the second time this has happened, the first time was only about 20 hours prior.

Do you think I'm correct in assuming that the overheating is due to the manifolds getting clogged? If so is there anything I can do beside pulling the four plugs and removing the debris? Could my issue be something completely different and if so what can I check?

[4Newfs 0]

If your engine has catalytic converters It could be they are getting clogged up which is reducing the cooling water flow through the manifolds?  As for fixes, the only one I'm aware of is replacement of the converters.

[scotchipman1 0]

My engine does have catalytic converters. I assume they are located inside the exhaust manifolds? I do think my problem is the exhaust manifolds/catalytic converters are getting clogged with the flaking debris. 

For whatever reason several of us that use our boats a lot exclusively at our lake are having the same issue. Our lake has around 1,000 ppm of dissolved solids in addition we have a lot of very fine sediment.

I plan to drain the exhaust manifolds more often and will see if I can run some fresh water through the system from time to time, hopefully this works.