You give no details of actual output. My suspicion is that tsr7 may not have been the best choice for such a small prop. You say that it spins easily so bearing friction may not be a big problem.

Even with the line resistance you are likely still stalled.

If you have no wind there is no cure, but if you have reasonable wind find another battery and try it at 24v. You should be clear of stall and should be able to get rid of the line resistance.

With 4ft tsr7 it should fly like crazy. Try it with the battery disconnected and cheek that it does. If so try 24v, that should let it keep it's speed up.