Just need a lot more information. Current prop, rpms, performance, etc. That model 21 TrX probably needs a 24 fury 3 or 25 Tempest. It will handle and carry a load well with 24 Fury 4 but won’t have a great top speed. The new 21 TrX hills are running good again. I’m running 24 Fury 3 on mine and I can run into high 70s.