hi all...well all i can say is liquid will carry heat away 2x better than air, the only problem is getting the heat through the motor casing to the water so in the case of that boat jacket, it would not work very well if used on a motor with cooling fins cut on the side.
i think the system has potential. maybe a pump on the rear of the motor, just a low loss pump.
looks to me like that pipe is car brake pipe made from copper and is really cheap to buy a roll. so bend it into shape as a radiator and wrap some around the motor as a cooler coil (bends really easy). then u just need a pump. hmmmmm.......
maybe a water cooled brushless e-maxx coming soon