Controller troubleshooting

[dr_destructo]

Hello to everyone! Been lurking on here for a while, lots of great info. I have a Marathon(pretty sure). I think it is @ 1991. I expected it to have the resistor-type speed controller, but it has an electronic/solid state s/c. There is a rod coming from the pedal and is connected to a small box with 2 levers on it. Behind the small box is the s/c. It all looks stock. Problem is when the pedal is pressed all the way the cart stops moving in forward. It will only go forward up to about 50% pedal. In reverse it works fine througout the entire pedal range. In fact, it seems that the cart will go faster in reverse(not sure if they are supposed to go the same speed in fwd and rev . or not). Any thoughts? Any idea what system I have. Not sure what you guys mean when you talk about DCS and non-DCS, series or regen. ANy help is appreciated. Thinking about maybe a 72 volt setup, but need to know what I have to start with.