Hiii...I have the same boat with SJN but mine got rudder (static)..using 380 motors and circuit boat..mine using 7.2v 1800mah..china made..but the the boat is not as fast as i expected..
I opened the box where the circuit board was placed..the circuit board is intalled with 3 relays..SJN, is ur boat also using circuit board with 3 relays? Maybe u have ideas in modifying it..