RE: Yamaha 704 control ??
Try the Yamaha parts catalog online. I just had the same problem, bought a new throttle cable, problem solved. Before I bought the cable I tinkered around in the control box. IMO, it's far more likely your throttle cable went out than something inside the conrtol box. It's easy to test though. If you unscrew the bottom plate on the control box, and unhook the throttle cable (then unhook it at the motor end too). You can push on either side of the cable to find out if there is too much friction in the cable, if there is a lot of friction, or it won't move, replace it. If you do go into the main control box, be careful, there are a lot of parts in there, and they all have to be aligned a certain way in order to put them back together.