From the NAMBA rule book:
Currently approved motors;
AquaCraft AQUG7000, Himax L36/56 7.2-18V – 6 pole brushless, HB3630 ProBoat 1500 brushless – 6 pole brushless, PRB3310 DYNM3835 A3630-1500 – 6 pole brushless, A3630-1500kv – 6 pole brushless, water cooled, marine motor. No modifications may be made to the motor. Except for normal wear, drive flats or keys, electrical connectors and water cooling, it must be run as shipped from the manufacturer. Power Limits: 10.1 to 15 Volts nominal, any chemistry. Maximum of 2 packs in parallel. Maximum total capacity shall be 10,000 mAh.
Good luck finding one. Many clubs used the P limited motor rules before the latest high power motors became available. ERCU uses the P limited size limits with a 2000 KV limit. They limit current with a 50 mm maximum prop diameter. NAMBA is overdue for a rule change. With the above motors any ESC rated at 100 amps will be fine.
Lohring Miller