Kind of redneck solution, maybe not that efficient. But guess no gear and enables even with a foil engine to be out of water, direct drive, only straight axle?
Jet Turbo Pantaneiro on google helps with details.
Not meaning to use this engine on a foil but only the propulsion part of it 
So if I understand correctly, water is vaccumed from the bottom and redirected backwards with a 90 degrees angle ?
Pros I see:
- engine can be mounted vertically in the board with rotating axis in the mast
- motor ESC and battery packed in same area
- waterproofing : only in the board (hatch, …)
- water expelled through the fuselage
Cons:
- Not sure about the efficiency.
- more noise and vibration
- fuselage section should be important:
Water pump propulsion like the first “jet surfboard” 40 years ago …
That will be super inefficient. The 90 degree bend means it’s for a super slow speed. If you want to go for a jet design. There much better ones available.
Checked some Youtube videos with the 6.5 hp and 3 hp versions. As a very inaccurate estimation looks like, at these speeds, probably same speed as outboard with roughly 30% less power. However i think with this design as outboard version, the resistance of the jet housing is huge. By no means don’t think this will be efficient but in a surf board version tho whole unit can be integrated in the hull so would probably work better there. Probably the bend can be re designed to a less steep? Somehow like the simple design, good idea. Efficiency is then another story.
Here some parts to this machine, impeller is roughly 15 euros!
And here a more developed version for outboards.
