How fast do you want it?
I modified a Super Hawaii for my friend who was running two modified 12 turn doubles 540 car motors in it for 26 mph. Which is a perfect speed for handling. (the boat has all stock running gear) The motors had brush coolers and motor plates all water cooled that I did. Running a prather 220 with stock drive train.

The problem was the 43 amp constant draw on the batteries. I just installed the new 12 turn 550 traxxas motors for the new rustler etc. I powered them with my left over EVX 14volt E-maxx speed control. I ran the motors in series so both motors would get 7 volts each. this worked well the amp draw dropped to 16amps per battery. (eve uses two battery leads combining the voltage in the speed control) So batteries where cool and the motors after two minutes run time at full throttle were cool to the touch. They were only using the cooling motor plates on the front. I didn't clock the speed on radar but it was very nice and the boat handeld even better without the dreaded spinouts when turning.

I am next going to try the Traxxas titan e-maxx 23 turn 550 motors which are wound for 14 volts. I already use them in the fighter 550, the Baltek (mini Hawaii) and the MRP Phantom cat all on 7 volts and the move them all in the 18-22mph range. They have more tourque and more rpm so I will up date you as soon as I get the time. (just got out of the Hopital) I still have time before the lakes freeze

I would try the traxxas 23 turn tritons if you want a drop in solution the are $23 at your LHS

Regards,
Chris
PS the 12 turn 550 from traxxas are also 23 bucks