CMI Header Temp.
 

What is the normal running temp for CMI headers? Should they be hot to the touch? Just installed a set on my new 454 mag. Started on garden hose and exhaust water got hot enough to steam (more than usual) and headers were pretty hot at the collector.Could it be that the hose just didn't have enough volume of water? This is my first experience with tube headers on a boat, so any help would be appreciated!

Depending on where you are located, hose water can be pretty darn cold yet (outside air temp is 50 degrees in WI today). With the cold hose water, it's going to steam regardless.

I can't comment on the collector area however...

That is normal for a hose. Put the boat in the water, they will be cooler.

That's what I have noticed. Any idea why?

When running on the hose my port header gets VERY hot. My star. header stays very cool. I don't like to run on the hose for anymore than a few minutes because of this. In the water they are both cool. I'm on well water and it is very cold and the pressure seems adequate.

BTW, I did the CMI / Merc. service bulletin that eliminates the bypass hoses this weekend. The only difference I noticed was when I drained the headers at the end of the day. The port header seemed to dump way more water than before.