Found this on another thread: Dead Kool O Matic Fan
Here is one answer from that thread:
Re: Dead Kool O Matic Fan
« Reply #4 on: May 21, 2011, 11:20:53 PM »
If anyone is interested I finally got around to replacing the dead Kool-O-Matic, I decided to go with a MaxxAir TurboMaxx and could not be any happier.
I removed the Kool-O-Matic motor and blades, and all the internal support structures, then went up top and loosened three bolts around the perimeter of the housing and pulled the fiberglass cap. The TurboMaxx went on right over the existing round hole, I bolted it too the roof with four 1.5' lag bolts through the original Kool-O-Matic base.
My Kool-O-Matic was never in working order so I don't know how much air it moved but the TurboMaxx moves a ridiculous amount of air, something like 1300 CFM, and does so on 4amps.
I purchased the TurboMaxx through Amazon for $258, I try to buy locally whenever possible, but the best price I could get was $310 locally, and $50 IS $50.
I highly recommend the TurboMaxx!