It looks like the same problem Wet-N-Frugal had. I was getting high temp alarms at low speeds, so after a day on the lake of alternately either high speed running or turn the engine off and run the bilge pump, it needs to be fixed. I would have mentioned the name on the tranny cooler, but like Wet-N-Frugal's the paint obscured the lettering. I believe it the same Sen-Dure part.
Thanks W-n-F for the thorough analysis and pics.
I can sweat copper, having done it for indoor plumbing, but I would feel a bit better if I could guarantee that I didn't mess up my transmission lines, so Cap't Rick, I will be sending you an email soon. It's a good time to flush the tranny anyway.
Bill