I run mine at 135*- 145*.
Its a single pass system, lake water temp plus 50* MAX.
Never run it over 160* ( hard water contamination starts coating everything )
Not 180*-195* either, its not a smog motor.
No pressure regulator on mine, more crap to fail. (does the Colorado river have sand?)
Adjust said gate valve to 130*ish underway, or 145*ish at idle. Done.
Hope that helps.
Dan'l