A friend of mine runs his "Strahl" (which should be exactly the same hull) with 1 900 size motor on 24 NimH cells.
This thing runs perfectly, I just remember he told me that weight was a big problem with the boat. If it is too heavy it is not running anymore.
If you really want to go with brushless motors I personally would use 2 motors. The rest is a bit hard to answer of no boundary conditions are known. So Iīm trying to guess a little bit.
So letīs just guess you are using 50mm brass props and you want to go 20 km/h the motors must have around 10000 revs under load.
At 4S Lipo this would be around 750kv.
At 6S Lipo 500kv.
So with 2 of these
http://www.hobbyking.com/hobbyking/store/__28693__NTM_Prop_Drive_Series_42_58_500kv_1300w_UK_Warehouse_.html you will be absolutely safe, also if you want to use bigger props or racing props with higher pitch.
They will provide you each with around 400-500W without generating heat problems.
These ones here for 4S
http://www.hobbyking.com/hobbyking/store/__38034__Turnigy_Aerodrive_SK3_4240_740kv_Brushless_Outrunner_Motor_UK_Warehouse_.htmlBut with these you shouldnt overdo it regarding speed.
They are suitable for 20 km/h but probably too small for higher speed.
ESC:
I always use the Roxxy 9xx ESC in my brushless boats, because they are simply the best I know.
Very good starting of the motors and smooth running also at low speeds (but still not comparabale to brushed motors).