What i mean by "goes wild" is i have no control of the throttle. The boat goes full throttle, stops, full throttle, stops, and so on. Its not always a perfect pattern though. Sometimes it remains under my control for a few seconds, but then i lose control of it as soon as I touch the throttle. When it is out of the water it works fine, but as soon as the prop touches the water it has a mind of its own, and i cant control it.

The problem has to be either in the speed control or motor. I still have control of the rudder when I can't control the throttle.

Its only 6 cells, but its a really high powered, high efficiency brushed motor (stripped both of the gears while trying to figure out exactly what it was doing). The drive shaft is a solid piece of steel, and the prop is some horrible radioshack plastic thing, only about 2 cm diameter.

Although the motor is grounded. It can sometimes have a lower resistance path to the water, so thats why i was thinking it was grounding to the water. I asked an electrical engineer and he said it was possible, so I don't know it should be excused as a cause.

I'm new to boats so I don't know what other information you need to help me. Sorry for any typos too :P