Finished my winter efoil build and slowly learning to ride it but am hampered now by getting a bad electrical constant buzz in the water on bare hands on the board when above about 50% throttle. First two sessions were fine, getting used to balancing on my knees and getting on a consistent “plane” but not on foil. Then during the 3rd session I realized my hands, placed towards the front of the board to balance and put pressure on the front to get on plane, were getting shocked continuously, and uncomfortably. I am running a 14S, 40Ah battery pack in a “Pelican” box also housing the VESC, and strapped to the back of the board. At first I thought it was my motor wires conducting to the mast, maybe through the holes cut in for running the wires in and out of the mast. But I am not showing any conductivity from the motor wires to the mast or motor exterior. But I am seeing very low resistance (maybe 0.1-0.2 ohm) between the motor wires and the motor shaft.So it seems that I have a semi-short somehow in the motor from phase winding to motor shaft. The motor still provides plenty of power (up to 5000W) when accelerating and about 3000 W when cruising around on my knees on a plane but not on foil, as it has since inception (I can upload VESC .csv file if helpful). While I can cruise around on my knees, in a wetsuit and booties, no-hands pretty well, I was just starting to work on getting up on foil and need my hands to push up and balance on the board and that is uncomfortable. If I was further along and getting up on foil quickly I might not care about the conductivity, but it is probably not good for the motor and I will probably leave a trail of stunned fish behind me. Any tips? I am not really looking forward to opening the motor, as I recall it is a little hard to get back together and well waterproofed, but am prepared to do so. I have other Flipsky and Maytech motors that have failed on me in my outboard 10hp motor conversion on a skiff, due to bad bearings or circlip or water intrusion and have opened those before to find burned windings, etc., so have a little experience getting the motors open and put back together. But hoping there might be some trick or common cause for this “shocking” phenomenon. Anyone have a spare 65161 or equivalent for sale? I want to get back on the water!
You are lucky as this could have ended a lot worse. It only takes a tiny amount of electricity to affect your heart rhythm - milliamp range - and it’s between your two arms so potentially in the path. Please fix it before launching again.
I also notice two things in your photo.
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Looks like the white prop bundled with 65161 motor - it’s too large for efoiling -well documented here.
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The battery box looks like it is right where your back foot should be when standing - might be camera angle but have a look at forum for proper placement.
Those connectors look like as150 and are not waterproof.
That is some scary shit. Better figure this out before you get on it wet again or I fear for your life.
I just reread your post and its not obvious to me how there could be an electrical path from phase wires to shaft. But anyway I think taking it apart is required. I have never done this this so cannot help there.
Somewhere on the forum is a pic of the 65161 opened up that might help.
Good luck and curious to what is going on.
Good points. Yes, I am using the stock prop for now. 7". Sounds like efoils are using higher quality 6". I need to review here to see which is preferred, is available in the US, and is an ok price. Let me know if something stands out. And yes, I am concerned about having the box in the way of the back foot. I can cut off some of the raised footpad foam so that I can move the box back some inches. On my knees it has not been an issue but that is not the intended use case.
The connectors are the standard issue gold plated bullet connectors. I had them each in their own “waterproof” cover made from modified “glands” and that worked pretty well, but I saw a small amount of moisture in one of them after a session so I thought the same as you, and I got rid of the covers and just covered the joints with waterproof heat shrink which I think is actually keeping them dry. I also tried tieing the connector bundle you see up higher to the box to keep them out of the water and it seemed to make no difference. That led me to think the problem is with the motor. And seeing the “short” (very low resistance) from motor wire to the motor shaft seems like confirmation. Interestingly the motor wires are “open circuit” to the motor case and mast and fuselage. So I suspect some winding in the motor is somehow contacting the rotor. This should not happen but I have had other issues with these “waterproof” motors on my outboard engine electric conversion using most of the same parts. What the path of current is, from my hands in the water on the board back to, is unclear to me. Here is a photo of my disassembled Maytech equivalent motor from 2 years ago, where some windings seem to have burned out. Anyone have a good way of repairing this? Seems like I will need to open the Fliupsky motor on the efoil to inspect.
For safety purposes and to be able to get back on the water soon, I should probably replace this motor quickly and the fastest would seem to be to purchase it on Amazon at the Flipsky listing, for $345 with free shipping, 2 day delivery, basically the same price as ordering from the Flipsky.net site with $50 shipping from china. I see that an aftermarket warranty is also offered by Asurion when purchasing the motor on Amazon, for $39 for 3 years. I almost never buy extended warranties, but in this case that is very tempting. Has anyone here tried/used the Asurion warranty on a Flipsky device with success? The fine print does not seem to exclude our use cases and the Amazon site was willing to put it into my shopping cart with the motor. I have not seen any good deals on the motor elsewhere, not on Ebay or Foil.zone or FB marketplace or Craigslist. The motor I am using that now seems to have the “short” I did purchase from a foil.zone user in the past year, in a package with some ESCs. It seemed to be new in box but who knows. And from now on I will check all fresh motors for conductivity between phase wires and the motor shaft. I checked this on my 85165 motor on my outboard engine EV and I see infinite resistance between phase wires to motor shaft our motor case, as I would expect.
Also, I do not think I have any leakage of electricity or water from my battery/ESC box since I do not feel any shock until the motor is powered at about half throttle. No shock when static/low throttle. I wish the battery box was the problem - would be easy to fix 
Flite prop. Search forum for confirmation if you wish
Anyone have a used one for sale? I expect they use a threaded motor shaft with pin, not splined shaft, correct?
Is the safe continuous motor power 3 kw, with just maybe 10 second peaks to 6 kw? I have not felt my motor get beyond warm to touch. But I am big and heavy at 6’4” and about 230 lbs. I expect that on foil I can cruise at 3 kw but when just on a “plane” and not on foil I am cruising at 3-4 kw at 10-15 mph with the white prop. But I do not want to “fry” another motor.
Is moving the mast fully forward in the mast track the equivalent of moving my foot stance also a few inches forward when on foil? That would give me a bit more room in front of my battery box strapped to the board.
My 65161 with fliteprop and gong curve xl gets 1kw onfoil on a perfect day at 25kmh. Get the fliteprop its the best bang for your $.
Good data point - thanks! Current price for the propeller from the Flite web site is $50 + $10 shipping in US. A good price if the performance is quite a bit better than the std Flipsky white prop and it saves me from burning out a 65161 motor. And a far lower price than say Flying Rodeo from what I see here.
Can also buy from electric surf co in Austin TX Fliteboard Propeller– Electric Surf Co
Price does seem to have gone up at some point, used to be $35. Still a bargain price for a good prop. I can usually get on foil with under 3kw with a 65161 on my 1300cm2 wing (but I weigh 145lb) and then cruise around 800-1000W. Even with added weight I would imagine you should be under 2kw easily while on foil
Thanks - I have placed the order there for the Flite prop.
Note with the flite prop you will need to ream out the center. It takes an 11mm shaft and Flipsky is 12mm. Can be done with a lathe or a drill press. Can also do it by hand with this 3d printed guide (how I did it)
Thanks - I am hoping it will fit in my mini-lathe chuck. If not I will need to get the drill guide printed somewhere - ran out of space for a 3D printer.