The PROP (electric sailboat) 

Folding props are the best. Lots of options out there but all are expensive. Added at least 1/2 knot under sail for me.

Holy barnacles. Dont have that problem in the Baltic.

I think you adjusted the angle of the prop opposite to what is ideal for electric motors. Electric motors have high torque at low rpm so an angle that pushes a lot of water is better which you didn't do. Conversely, you will likely need an extra gear during regen, if possible, to generate sufficient since regen seems to require high RPM instead of torque.

Spin backwards?

cool project man, but you need to take your video editing up at least half a notch: show us the folding prop when you are talking about it, not in an extra clip at the end. Personally, I hope you DON'T waste your time on trying to make the videos seem "professional" and instead do boat stuff and tell us what worked and what didn't, but at least some bare basic cutting in some photos or other video to show what you are talking about instead of your face is needed. Taking videos without talking, and than narrating over them later can also be a great workflow that doesn't necessarily even use more of your time. You briefly mention relevant stuff about your setup without explaining any of it (cutting in a clip of the engine room during hydrogeneration would have been great here. With a bit of organization you can recycle good footage in a fraction of the time of making new footage). Is there another video somewhere where we can can see all the stuff that is making the noise you talk about? I would be tempted to solve that problem isntead of getting a folding prop, but I am sure you thought of that already so I'm just sitting here wondering why. Part of my plan with converting to electric was to use a giant, cheap, fix-blade prop, but it seems you went that route already and didn't like it too much... keep the updates coming.

Yes he did the opposite