Not sure what kind of fryer you have, but I bought the Bayou Classic model. The first time I brewed with it, the flame wasn't going very high and wouldn't change no matter how high I turned the dial. After I turned it back and forth a few times it seemed to "open up". You'll know when this happens because the flame is 12" high and it sounds like a jet engine. No kidding, it's hard to hear someone talking just 5 feet away if you're standing next to it :rockin:.
If you have the same burner I'd check to see if your dial is stuck. The other thing is to make sure you fuel/air mixture is correct, which can effect the heat of your flame a great deal.