voltage is not important is starting, its amperage.
the smaller lead acid batteries wont have a chance at starting bigger engines, they cant supply the amps needed, your car batt is 12v, same as the other lead acid batts, it can just deliver a whole lot more amps. one thing you could try it hooking you starter to your car batt and see if it can turn the ys over, if not you may need a bigger starter or you need 24v
some of the car batteries still cant deliver the amps for bigger engines
the solution it lipo or a123 batts, just make sure you dont over discharge them or your in trouble.