Here is my prop for a flipsky 65161 motor, still working on epoxy coating and sanding mine for testing.
This design is around 58% efficiency cruising at 1500 watts, 16 MPH
Looks like a 2 blade version would be around 63%, I left it 3 blade because my board is very difficult to get up on plane and the loss in low speed trust may make it impossible on my setup.
Top speed I am shooting for higher than 25 MPH
https://www.printables.com/model/576544-toroidal-prop-for-efoil