RE: Just Purchased: Aquacraft Rio EP
i'd go with brushless from the start, motor size would be a 36mm diamater with 60mm/70mm lenght (3660/70) feigao do some good motors for a reasonable price, a 540 long or xtra long will be a good choice (around 30k rpm on 6s), when you have the motor you can then decide what esc, battery to use, i use a 100a esc (watercooled/proofed) which i'll be swapping out for 120a esc, try offshoreelectrics.com for all that you need, they can help with setups aswell