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Mikael, my hats off to you and your fine product and sweat you poured into it. My apologies if in any way I seemed to criticize performance of your craft, far from it. I know nothing of it, and electric is going to be the only way in the near future. The context got shifted toward it somehow.

My general skepticism regarding hydrofoils comes from, quite frankly, not seeing that much damage with them because they don't exist 'in the wild' so much here to establish a conventional sense for most U.S. east coast watermen. Plenty of other issues that everyone I know is familiar with, most commonly groundings and striking objects, and occasionally catching cage lines on props. The petrol-era weight bias sticks around and this is where I hope you show us very wrong. I'd love to see some rough water videos of your C-7.

My original response from where everything else stemmed from is that right now this isn't a practical conversion for a common man with something like a 27' cabin cruiser, certainly not in the pocketbook. I do not know how much the C-7 costs, but was my sticker shock that far off?

Water under all those videos on their homepage is what we'd basically call smooth as glass. That's definitely a calm +/- 5 cm wave range.

Here is what a 1.2 meter one looks like, just exiting an inlet: https://www.youtube.com/watch?v=rV41E9PQwiU

Check out the electric co's site, and maybe it'll explain it better than I could have at a broad pass. But that inboard was their entry-level motor that actually existed.

I suspect their power declaration is marketing language claiming burst power, and that its nominal cruising range is well under it but regardless of any of that, the batteries costing $180,000 is still an issue.

Edit: forgot one important thing for that power matching, the weight. Replacing an engine and full gas tank -- the electric motor + mid-range battery pack overall adds about 2,500 lbs to the boat, so it'd be a 7,200 lb boat at that point and I'm not sure I could trailer it anymore.

Imagine cruising at 30-40 mph, angled so you cut through waves perpendicularly. Mostly you head straight, but you do need to lazily avoid some crests and troughs, aiming for that sweet middle. You then see a mostly submerged log 30 feet ahead, just barely under the surface.

You now have two choices, steer to the left or right of it. Those split-second decisions have consequences, depending on which way the prevailing waves are headed. Say if you turn toward port, you might be parallel to the waves which you never want to do: they can capsize you. So you don't turn to port.

Heading toward starboard might be a better choice, but it's still not perfect - you might head toward a crest that will definitely slam into your bow violently. Or there is another boat wake you now have to deal with that wasn't a problem seconds ago. In either case, you need to alter your speed to either avoid it or cut through it more gently. You start dropping off plane, cut through a favorable section, and then angle yourself and go wide open throttles to miss a trough. Maybe you rise back on plane before you avoid it, or just slightly afterwards but on most V hull powerboats doing all this is not a problem. In normal traffic, this might happen a few times a minute.

But hydrofoils have two things going against them right there. They have massive drag at lower speeds and thus maneuver poorly in an emergency, taking more time to accelerate on plane or change direction. Then the weight ratio is a challenge: they need a lot of power for cruising speed, so they weigh more than you'd expect and then weight management is one of the primary design concerns. That all means the propeller is optimized for power over acceleration, and that means that these three congruent design choices have painted you into a corner, limiting collision maneuverability. Hydrofoils handle rough seas far worse than any conventional hull shape and more importantly, colliding with anything underway is far less forgiving than striking an object on the bow or outdrive.

Emergencies notwithstanding, being normally outside a propeller's designed operating range and you have cavitation and ventilation problems, which then erode the propellers. And that weight constraint means fewer seats, fewer people to carry, so less efficient per capita.

Engine lost compression in two cylinders on my 5.7 GL Volvo Penta. ~ 300 HP, leaky exhaust riser. Took the opportunity to look into an electric option that can bring a 4,700 lb boat on plane, comparable power that is in production and available.

- Evoy hurricane inboard, 600 kW: NOK 1.497.000

- Battery pack: medium range, 252 kWh: NOK 1.476.000

In US dollars, that's $360,000 and I'd have to ship it from Norway. Closest second option was about half that price using BMW i3 batteries, at half power. Meanwhile, a new marine engine was $10,000 by comparison, or to repair exhaust and rebuild to last another 17 years, $5,000.

Boating is a luxury and I can't excuse it in environmental terms, same as I can't excuse electing not to walk 2 hours to my local starbucks for a consistent grande pike I enjoy in favor of brewing my own. But marine electric is currently nowhere near being a practical solution, and you cannot hydrofoil in all boating conditions, especially in choppy waters, or where there are seasonal floating obstructions.

Boats do have notoriously small efficiencies (1-4 mpg) in both displacement and planing modes, but consider that for an automobile to have its 25 mpg average we pour approximately 124,000 gallons of crude oil per mile every 5-10 years for a two lane asphalt road, a coarse byproduct of refined petroleum.

My whole point here is not to equivocate in any terms, but that it's easy to overlook externalized costs. Moving an object anywhere is a difficult problem.