Full size electric boat controller questions

[lincpimp]

Ok, so I picked up a boat!!! It is one of those small, plastic, 2 person pedal boats, but it does have a trolling style motor on it.

Only issue was the motor was shot, water got in and rusted the internals. Luckily I had a freind with a damaged bass boat trolling motor and he gave it to me. Between the two motors I got a working example.

Problem is the new franken-motor is more powerful than the original and the internal wiring in the boat is not really good enough to run it.

What I am looking for is an alternative.

Dc motor, runs on 12v. I use a car battery. The motor has a large resistor mounted in the nose cone that coupled with the existing rotary switch gives 5 forward and 3 reverse speeds. I do not really care about the variable speed, as it cannot be very effecient (think old tamiya mech speed control).

I would like to have forward and reverse.

I am guessing max amp draw will be around 50amps. Might be more, but I did some research on trolling motors and that seemed to be the norm for a trolling motor on a bigger bass boat, and my pedal boat is ALOT lighter, so less load.

I think a simple switch would be the easiest, but I do not know the terminology (sp?) to describe it.

Basically the switch needs to take a pos and neg feed, be able to switch polarity on the output wires, in order to run this brushed dc motor in both directions. This switch would need to handle 10gauge wire, and not melt under a 50amp load.

What do you call a switch that can do this? It would be nice if the switch had a centered position that would not pass any current, thus acting as OFF.

I know I can use a pair of 5 pin relays and a 3 pos toggle switch to do the same thing, but I figured you electric geniuses could point me in a simpler direction.