I've patched up enough of those Curries in the last few years, this should be up my alley. It was mentioned they were confused on if this was a scooter or a bike, you didn't respond to that. I suddenly realized I've never seen the separate part for the controller on the bike, maybe it's inside the batterpack, I'm not sure. I went and looked mine with the conversion kit over, no sign of it. But since you have the controller in your hand I'll assume it is the scooter.
First of all, my best guess is you should just put the 36v Currie controller on it. Look how cheap, although darn, out of stock at the moment. https://www.curriestore.com/product/eZi ... oller/491/
It's for the 1,000 watt bike. There is even cheaper stuff at Scooterparts4less.com, etc, (Bring your own wiring diagram) but I'm holding what is probably the identical controller to yours in my hand and looking at the pic of the 36v Currie to see a match for every plug on this controller. (And then some.) However, look for a 5 or 6 pin throttle plug on yours, the 36v says it's a 5 pin. 6 would mean you need another throttle. But here it is WITH the throttle. http://www.monsterscooterparts.com/curr ... ottle.html
Just remember, they SAY they should work, but sometimes you find yourself having to rewire. http://electricscooterparts.com/hookup/ ... wiring.htm
Now, about those batteries. Are you SURE you don't have a pair of 12v, 10 amp batteries? That is what I expect to find in any 24v Currie system, haven't seen anything different yet. I think you're already getting all the voltage they can give at 24v. To go 36v, (As others mentioned, really as far as you want to go) you need one more cell, I recommend you replace all 3 at once because mismatched cells destroy each other quickly. You'll also need a new charger. http://www.monsterscooterparts.com/scsts1elscba.html
I ran 36v on the S350 with not much of a shunt mod (Extra wire soldered onto the arch you'll see if you open your controller) and I guess the way to put it is my inadequate little scooter became less inadequate. She's have to say for herself if she's happy with it that way. Of course I'm the kind of guy who rides these things after he puts meathooks on them and gets going 45mph downhill. I should do something about the brakes, etc. I should guess a bigger controller would accomplish more than a shunt mod, but only one way to find out. I thought the motor got pretty danged hot before, not sure it's worse now. But I don't really run it CONTINOUS when I ride, I get to speed, coast, etc. No suspension, not much brakes, I guess it's not good to put too much into upgrading this thing. Next time I have a 36v to fix I'll try the controller on it.