[redshift]

IF gearing is producing the torque/speed you want, then it's time to reconsider your motor mount. The motor mount, while open, is still thick. I don't think you have one-quarter of the fan that motor needs... and the mount may be acting as an insulator more than a heatsink. You have enough of a hole to use a larger fan, and I would consider one on either side (if you have the room) blowing inward, so that the top is just an exhaust. The fins can't do their job in a semi-enclosed mount like that IMO.

If you have to make more relief for air around the inside, it won't show. But it could be a big help.

Or just wait for colder weather lol... won't be long!