New to this thread, but it is obvious that the big Johnson motors originally fitted were a terrible choice of motor for a scale ship, more so four of them! Given the lack of info on the currently fitted motors I would suspect them of being the problem. That and the 12v power supply. 12v is great but you need to match the motors to the voltage, and I think this is what is going wrong here, again and again. I feel your local hobby shop is giving you some pretty duff recommendations on motors. Which motors are they, specifically? Give us a link to check out their rpm etc. If they turn out to be too fast for 12v, which will trip out the speed controls as described, the easiest fix is to drop down to a pair of 7.2v NiMh batteries. Lower current, less chance of tripping out. But we are getting ahead of ourselves.. what are the motors, exactly?!