Did you get the one that was listed on Ebay?
I have an MRP Fountain, and yes, they are very light!!
I was toying with the idea of getting the one on ebay and removing the to outer motors and shaft bulbs underneath. Then i was going to use the center drive with a 3674 -4 poler from Hobbyking on 6s. The boat doesnt need anything more than a 3674 or a 4074 for all the speed it can handle(it was made to go about 20 mph)
This is the motor, its backordered at the moment - http://www.hobbyking.com/hobbyking/s..._Inrunner.html
Here's a 4074 - http://www.hobbyking.com/hobbyking/s..._Inrunner.html
Got any pics?