I think that the water circulates by itself, like a radiator at home (hot-cold-hot), looks interesting.
this is my recent way to cool (honestly, Its not my own idea):
I've put a vent on the back, blowing air through the motor:
a nylon-sock keeps dirt away:
at least the heat doesn't stay inside.
I've read about this guy who drilled holes into his kb45, and put a vent on the back (boat use), that's where Ive got the idea. I did that with my kb45 as well, temp was around 40 deg. c.
on top I have an other vent beside the motor. sure, the higher the efficiency the better. but not everybody can afford a neu, and unfortunately the medusas aren't available here in europe. this one is a cheapo (36-88-49), but quite okay.
don't forget, most electric motors in industrial use also have vents.