Exhaust clogged, maybe?

[Casey-2500]

Hey guys I have a 95 hx that’s overheating. Blew all the lines and I replaced the wear ring. Its circulating water both on and off the trailer. I didn’t pay much attention when I first started working on it but the lower portion of the bent pipe that leads back to the muffler is black. I disconnected it from the muffler and it doesn’t seam clogged with anything. What could cause the exhaust to over heat like that and what are some ways to fix it?

 

[POPPS]

Is the drain line clear?

 

[Casey-2500]

Would that be the line that goes from the top to the cone or is that the one under the manifold?