Just for prosperity's sake here is the info I fudged together on an electric setup fo LOCURA over a couple of e-mails (Hope you don't mind)
I've got a 60 inch hull that I'm running electric in, It has 4 700s in it, the fastest its been so far is 16 KPH (working on that just changed from Lead to Li-po batteries) so I think the motor you have is too small, (just ran it on the weekend except for an Receiver failure I know it was over 25 Kph now)
BL3 Brushless Watercooled Motor 3650. 3300 rpm per volt.( High rpm) For 8.4 to 12 volts. 3S to 4S lipo or 7 to 16 Nicad or NIMH packs. Mounting hole spacing of 19mm or 25mm. Diameter 43mm, length 63mm., shaft diameter 4mm. Replacement for 700 size motors but MUCH more powerful. I have been assured this will take 18.5 volts!! I also have 2 packs of 18.5 volt 4000ma lipos and the ESC mentioned. I wonder if I have any of the recipe?
Now I'm by know means an expert but I think I can get you in the ball park.
If you can, get 6s lipo, the maximum the ESC can handle 4s means higher amp draw and a higher KV motor. A Zenoah spins around 15-17'000 rpm but 30 Kph can be had by a stock brush cutter motor that barely makes 10'000 Rpm, so a motor with a Kv that matches up to that figure at intended voltage should give similar performance. 10'000/ 18.5 gives a KV of 540, bump to 600-650Kv to give a loaded rpm. At 22.5 volt (6s) 440Kv, a kv of 500 including fudge factor will do the job. A large 55-50 or similar size outrunner (cheap from HobbyKing.com) with the above Kv ratings will work using 55+ mm props. You could go with a Neu inrunner (very expensive) with similar Kv as well.
I would expect an amp draw of around 40-50 amps with a 500 Kv motor and 6s Lipo, a bit more with the lower voltage
Regards Nick