I plan on running four of these in a WWII Lion, direct drive at 6 volts, with the Mtroniks viper ESC. I don't think there'll be any problems getting up to big-gun speeds, and I'll use the programmable endpoints on my radio to set max speed.
I think that a speed 400 would be an extreamly poor choice for a direct drive motor. To get the shaft turning at a RPM that will dirve the ship at the correct speed, a very low amount of full % of the ESC will be required. So the ESC is likly to be trying to disipate alot of energy as heat. A good way too cook something. A beter way would be to use either a lower speed motor, or gear reduction. At a full 6 volts, your 4 speed 400 motors are likly to pull 25-50 amps of current. (depending on prop type) Start up currents will be larger. You won't have any problem making enough speed- but you might hydo plane. (unless your wireing goes up in a puff of smoke)
Because I wont be running anywhere near max capacity in the motors, amp draw won't be an issue. I'm actually running two 25 amp controllers, with one of them set to give more thrust from the inner props, hopefully giving more wash to the rudder. Prop rpm isn't really an issue either, as the props I'm using have a fine pitch. By the way, Mtroniks makes esc's up to 75 amps in marine, and a huge 140 amp truck one, which is waterproof.
Try www.huntersystems.co.uk. Prices are hard for me to judge, as I'm in Australia, the prices are in British pounds and not in US dollars..
