525 header getting hot
 

Starboard motor port side header is getting a lot hotter then it should be. Put new water pumps in. Just got done putting new transom assemblies on. If I take the hose off the diverter that connect to the top of the header there is plenty of water flow. There is non to very minimal water coming out of the tail pipe. Any idea what the issue could be. Thanks in advance

60 views no one has experienced this?

Partially clogged heat exchanger?

clogged tail pipe.is this on the garden hose or in the water?

Restrictor in the tailpipe inlet plugged? Cmi headers have a drilled out pipe plug in there on the later ones.

That was my next move is to take the exchanger cap off or back flush it.

At the top of the header is the hose that dumps the water into the diverter/tail pipe/ muffler. If we put it in silent choice the header still stays hot.

Is it possible that the heat exchanger could be partially plugged and not allowing enough pressure to the header? Like I said It seemed like there was plenty of water flow coming out the top of the header

You can grab some cheap hose and guage at any hardware store, temporarily replace the existing hose to the header with it, and check how the pressure compares with the other header. If it's high than you have blockage in the header. If it's low then it's a supply issue.

As mike asked is this on a garden hose? When you disconnect the jumper hose the water simply takes the path of least resistance.

I noticed that you said you installed new water pumps. Do you mean impellors, and if so were the old impellors wiped out and chunks missing?

Boat was ran in the water in the slings

Replaced the water pumps over the winter cause I had purchased the boat in November. Before the boat went to storage it did run in a well for a hour or so and there was water coming out of that muffler. (I have video) there was water coming out of that muffler when I first splashed it this year. Had a u joint blow needed to pull the motor to replace transom assembly. Put it all back together and now have this issue.

I did back flush the whole system. I forward and back flushed the heat exchanger, check the oil cooler for blockage, back flushed the header, ran water in the diverter port all seem to flow good

Is it possible to have gotten a slight twist in the hose from the helmet to the transom assembly, I remember reading to caution against that while reassembling mine.

Not unless they did it at Mercury. But I will check that

My header overheating issues were caused by a clogged heat exchanger. The engine oil cooler was plugged. Looking at the front of the engine, the cooler is on the back side. Its tucked in tight and hard to get to. Unscrew the center bolt, Open the left side and clean out the debris. I had an old impeller stuck in mine. Back flushing didn't do the trick.