Matty,
From other posts I've read, those boats are around 10" long, a speed 600 would run a boat 3 times that size.
Also, a brushless controller will not work with a 600 motor as that motor is not brushless.
The 600 motor will draw more than 12 amps so you also need to watch that.
A few others are building that style boat here and looking into motors around the 280-400 range I think.
You could use brushless, they last longer, are more powerful, but are much more expensive.
I'm not sure you'll get too many suggestions without more specs on the hull size and what you are trying to accomplish.
Check out http://www.rcuniverse.com/forum/m_3706287/tm.htm and www.microhydros.com also.