FWIW I reckon directing the exhaust through the prop hub instead of that cone affair would improve efficiency.
Also feel that the hull is to different (unproven?) to accurately assess performance of the drive system alone.
Also (II), the torques must be monstrous. Typical prop speeds on a 14-16" prop are about 3K rpm. On prop diameter that size could see rpm dropping to half that to keep tip speeds under control, therefore gobs and gobs of torque.
Also (III) interesting is the rear flow control fin. Conventional wisdom puts the prop in as clean, undisturbed flow of water as possible to maximise efficiency (think Volvo leading prop jobbie). That fin in front will be creating some turbulence, reducing efficiency.
Finally, in the clips the props are at best only just breaking the surface of the water - in reality they are running as virtually fully submerged. Hence no rooster tail.
Bet slip is low though.
Just some humble thoughts from an enthusiast.