525 CMI , Hose from header to tail pipe ?
 

I do not own CMI headers so I am probably WRONG, but...it seems to me that the connection from the distribution tube at the head should NEVER be connected to the tail pipe,,,cause it could lessen the flowrate around each header pipe. Wonder why that was done?

It would seem that you could be "bypassing" the header tubes and running the majority of the water flow straight from the tube to the tailpipe! I bet those "pipes" got really hot, especially when idleing along and there is not much water flow.

UPDATE!
Here is a "factory picture" of this kind of connection. I really am puzzled by this short circuit connection bypassing the header tubes.

On my stock 525 headers, the pipes do not get hot either at WOT or at idle, so the system does work. However the similar CMI headers for a 496 do not have this bypass hose. Beats me why it is like that, but don´t mess with a running system, specially when Merc Racing has been running it like that since about 2002.

The only theory that I can think of is that by encourageing the water to flow along the distributor pipe, the quantity of water that can flow up into each header tube is equalised. I also presume that there is more water running through the raw water system than the headers can handle, anyway.
I would run the two hoses into a T connector and run that out of a hull fitting on the starbord side under the rub strip. This will give you a visual of how much water is running thru the motor, at speed. If you fit a regulator into it you can restrict the flow if the headers are getting too warm.

To answer your question, Yes that is ok. Mercury racing has CMI put two bungs in the tail pipes for a couple of " debatable" issues. Your stock sea pump can not, and will not flow more water then the CMI headers and tails will flow. The screw in restrictors in the tail pipes are there to balance the flow of water that comes out the heat exchanger. Trust me, it is different from each side. Call CMI they can explain it to you.
Bawana