Although I hate to see everyone leave and head over to efoil.builders, we need different sections for this type of build. The eskate forum here on ES was ruined when esk8.builders started. I do wish the mods here would have things like subsections where we could discuss items like ESC, prop size/shape, motors, foil and on and on. We'll end up with a 400 page thread if not and all the important info will get buried. Efoil.builders looks pretty chaotic right now too, but there are tons of informative posts already.
I also hate when guys try to monetize the info - but I guess everyone has to make a living somehow. A kickstarter for info though?!!? I can see selling parts for an efoil. Someone could do a whole setup with prop, duct, motor, esc and you bring your own foil/foil board and easily make cash off that. Kind of like how the eskateboard thing went.
I saw this yesterday which I found interesting.
The current prototype version can run for an average of about one hour per charge of its removable battery, and reach a top speed of 15 to 20 km/h (9 to 12 mph). Plans call for the first limited-edition production model – the Hydrofoiler XE-1, pictured below – to be faster.
The Manta5 has an aluminum frame, two carbon fiber hydrofoils that provide lift, and a 400-watt motor that augments the rider's pedalling power to turn the propeller.
So if the foil has 400w and the rider maybe 200-300w, we are talking under a 1000w total. Also the foils are way different than a surf foil. Why do we not have something like they are using? Last - the prop being a push design would be better for an efoil for safety reasons. Your foot/leg will not be as prone to be in this area because of the front foil protecting it.