Hi Spearfish,
If you want to run at scale(ish) speed, get a brushless motor, that will spin roughly the same rpm as the 700BB 9,6V , which is a 1200Kv motor (accounting for the 69% efficiency of the 700BB).
Compared to the 700 motor you'll have instantly more torque and runtime, due to the much more efficient motor.
A Ø 36 mm motor already is more powerful than the 700 motor.
Keep in mind the low end response of a brushless motor isn't nearly as good as a brushed motor, specially with the higher Kv inrunners, which tend to burst into life at 1/3 throttle, making crawling along an ilusion...
I have the 'best' results with low Kv outrunners combined with a car ESC, but even that low end response doesn't come near my brushed set-ups with multipole motors, where you can count the revolutions, using a relative cheap controller.
I assume you've found this thread:
http://www.modelboatmayhem.co.uk/forum/index.php?topic=39278.0Plenty of power using two outrunners!
Regards, Jan.