Radical New Propeller Design... Sharrow?

I don't see any bolts in the picture Carl posted.

And I misspelled the name. It's Ringfeder

Yeah, except Sharrow has doctored the baseline test results once again, just like their outboard tests. Here's an independent test of the same exact Neptunus 650. Look at the speed at 1700 rpms as well as other rpm points. When you compare the real Veem test, the sharrows don't gain anything.

Neptunus 650F (2023-) | BoatTEST

Whether the results are doctored or not, I haven't spent any time investigating as the RPM and speeds you're showing with your link are similar in terms of nearly a push in the delta.

But compare the props at idle to displacement speeds, and the delta is meaningful. So if you're cruising at displacement for range and conservation, or if you're trolling all day for fish etc, the difference appears to be meaningful (and below the levels of your chart link).

Those are wrong/doctored also as hull speed on that boat is just under 9 knots and after that she drinks fuel.

You are clearly not drinking the KOOLAID.