Please, please, please, stay away from those crappy RTR electric boats!
With some rare exceptions, the ones with the 550/540 motors aren't built for the customer to enjoy, but for the moneygrabbing manufacturers, and are not worth the shipping costs, and they certainly are not fast.
Take a look at
www.offshoreelectrics.com for some RTR boats that are worth spending your money on.
Or, even better, get an epoxy/glass hull with the propshaft and the rudder allready fitted and fit a motor and electrics to your liking and budget and have years of running fun!
www.mhz-engines.com or
www.mhzusa.com
While you're at it, make a floodchamber in it, so it will self-right after a flip.
Please consult a forum such as this when you have narrowed down your choise.
Regards, Jan.