Can't seem to get up to temp

Just purchased the Pro Series LP smoker and we're using it for the first time.  When filled with pork butts, the smoker can barely get up to 175 degrees.  I observed the flames while set to the highest temp and I'm getting maybe 3/4 inch blue flames which just don't seem high enough to get the unit up to temp.  we plan to use the smoker at a festival and could really use any suggestions for getting the temp up past luke warm.

Ed