The RTR Impulse 26 is a great little boat - but it's a bit pokey for my tastes. I did a little research and found a suitable 3S power combo - the Turnigy ADS400L 3700kv motor driven by the Birdie 70A Boat ESC.
What a difference the brushless power makes! I recorded a 49km/h top speed (around 30mph) which made the boat a real blast. I was impressed with the hull's stability as well. Even in the mild chop it held pretty steady.
I was pretty happy with the 70A Birdie ESC, except there was no reverse! Not much need for it at these speeds however.