My brinkmann turkey fryer doesnt get up to boiling temp

Hi Larry, W/D here. Just got your question so I'm a bit late in getting back to you......
The amount of heat delivered at the burner is dependent on a number of things, and we'll take them in the order of most likely:
1st, The gas tip must be clear. It's possible for critters to build nests in the gas delivery piping that can plug either the gas delivery port or the air side of the mixing venturi; both will give you a reduction in BTU's. Compressed air can be used to blow out the air side of the venturi. The orifice for tha gas can be cleaned with a thin wire, or use a tip cleaner, available at a welding supply store. These are inexpensive.
2nd, The burner proper can become plugged at the ports where the mixed gas/air combusts. These can be cleaned with a small drill bit,sized to the holes, and just passed back and forth to clean them out. Compressed air works well to remove any particles remaining.
3rd, The regulator may be defective. If this is the case, you'll need to replace it as it contains no user serviceable parts.
4th, the in-line regulating valve may be sticking in the partially open position. This is difficult to diagnose, however, and is more of an assumption, after all other causes are eliminated. The cure for this is replacement also.
Hope that this was helpful to you.
Best regards, --W/D--