Direct drive outrunner with direct water cooling

Thanks @VeFoil and @Clarin

making some progress now, Just have to design a duct for each propeller :confused:

Motor stators epoxied:


Nice job on motor epoxy!!!

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Its amazing how these simple ideas grow. Thanks for your further development, this was intention. Although i think the coating shown is too thick.

Do you have a video and or supplies required to do this you could share? I’m working on another type of project and it requires an out-runner in water and I would like to do this as well.

Hi im a new user to the this forum and have built an electric skateboard about a year ago, This is probably not the right place to ask this as its off topic but would anyone mind pointing me in the right direction. I do not have a 3d printer or parts to machine so it would need to all be buyable. Thanks

Take a look at Pacificmeister’s design and read around the forum a bit to get going. The efoil scene is less developed than electric skateboards, so you will be on your own somewhat when it comes to exactly what you’re trying to accomplish. Good luck!

Im completing an efoil builders kit where everything is plug-n-play from parts, to propulsion system, to board, to waterproof remote control at VeFoil


Yesterday I tried to run my Hydrofoil surf. So far it went wel, but i could not het enough speed to het On the foil. Some how maybe my prop size is to big, so im going to trim it down a bit. Im running a turnigy rotomax, direct drive under water, with an toro beast 200A esc, On 8s lfp 45ah… from the sound it felt like the esc was hitting its 200A limit Or it felt out of sync?
This is a car esc, and maybe not suitable for running a multipole outrunner. So I need to find a suitable Esc that could handle 8s and at leest 200A+ that I could connect to my heat sync. The bottom of the board is a big aluminium surface. Had annybody have a God experience with a God price/quality esc? That can handle multipole motor 200A+?

Batterij: 12 Cell ~ 14 Cell / 44.4V ~ 51.8V
RPM: 195kv
Max stroom: 150A
Watts: 6600w
Geen belasting stroom: 44V / 4.8a
Inwendige weerstand: 0,013 Ohm
Gewicht: 1916g
Diameter van de schacht: 10mm
Winding: 8T
Stator Pole: 24
Motor Pole: 20
Stator Diameter: 101
Lamineren Dikte: 0.2mm
Voorgestelde ESC: 200A 14S Compatible

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What motor do you have?

i love your built!
i run 8S as well , hitting 32km/h and counting 25H (40mm inrunner with gear 1/6 so 130KV), my esc “recorded” for hard take off with 90kg and 1250 fornt wing:
165A with solas propeller 190mm diameter and 6 pitch
205A with FR propeller 135mm diameter and high pitch (9?)

so you can hit easly 200A with your motor, because high torque before rpm, big propeller with high pitch

what i would do.: cut yes, try the 350P10 2 blades torqeedo or solas plastic

as the esc i am happy so far with hiefi, i will go to 12S to get the amp down (after lipo burst on voltage sag) , good review on this one , and good price , i order one of this; you will have to make your own cooling


Thanx Alexandre.

I Will cut down the prop size and i ordered the esc You sugested. Lets wait for that and get better resultaat i hope.

@Johannes “out of stock”! :slight_smile: that was you? mine it’s delivered tomorrow, you can get the bluetooth module as well for iphone live data

DON’T install the software on C/: :wink:

From my experience with direct drive, the ESC timing needs to be set to “HIGH” or 30 degrees for 12 pole out runners, otherwise they lose sync with a bad squealing noise…

Also I believe you should cut the prop down as well as your motor is fairly high KV at 195. Try 130mm Diameter, that still could be to large.

EDIT: in my testing today I’ve actually found 24 degrees or “medium-high” to be better for my motors (ie, don’t lose sync), sorry for the change of info.

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I don’t yet, plus I don’t want to release everything until the system is perfect. Once i’ve got it tuned well so it is as efficient, and safe! as possible I’ll release it because I think the parts I’m using aren’t the best choice…

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it would be easier to make inrunner rotor as the prop and the duct the stator to increase the diameter and the torque of the moving mass as thrust .lower current and less drag also carbon fiber duct to seal windings and carbon fiber prop.magnets inside carbon fiber prop like a ductfan rc plane you wouldn’t need but the 6 or 7 inch duct diameter run cross braces and cermic bearings for rotor propeller.

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just throwing it out there but felt like i should give you another way to see if it would help with the torque and sealing problems but don’t steal my design for a new trolling motor.!just kidding 20180810_095617|281x500

Lars, there are many places online that will print 3D files for you so you don’t actually need to own a 3D printer. Example:

I would recommend using a lower KV motor unless you’re planning on doing a jet system. Have a look at the SSS 56114 360KV motor. That’s the one i’m going to use because it’s an inrunner, meaning it can be easily cooled in a metal tube with thermal paste.

For the ESC, lots of people are using the SEAKING 130A with lots of success. I think I will use an Ebike one as you can program the battery output amps for more control without having to use a BMS and will instead balance charge my custom 18650 battery pack. This one looks good for me. High current capabilities to reduce the chance of burning it out.

Here is the seaking:

The propeller will depend on what setup you end up using. Mine is going to be a jet system so will be an impeller at roughly 60mm diameter. Propellers should generally be metal for structural stability. Heres one on Banggood, however, you need to get one with the right pitch angle for the correct amount of torque/speed.

Seals and bearing will be needed to keep your shaft from vibrating and moving. The SSS 56114 has a 10mm output shaft which I will be converting to an 8mm titanium shaft using a coupler. So, I will need a ceramic bearing ( Won’t corrode ) with an inside diameter of 10mm after the motor and one later on, near the ‘propeller’ with an inside diameter of 8mm. You will also need oil seals to keep the water out. Probably 2-4 of them. They need to sit on your prop shaft tightly to make sure nothing enters. Some are sprung so keep the pressure on the shaft which is probably quite a good idea.
Have a look here:


You can get cheap ones on Amazon for RC cars that plug into your ESC IF IT HAS A BEC Which is like an external power slot of like 5V that you plug the receiver into.

Here is one I was looking at for testing. It’s not waterproof so will have to put it in a bag or put a condom over it like @MaxMaker :wink:

Others may have more experience than me in this field so don’t fully take my advice. :slight_smile:

Cheers, Owen.


Are you using a drive shaft to transmit power to the propeller and pod with a 90 degree gear at the top and bottom?
The housing looks like it holds a motor so I wondered if the motor is from you non foiling power surfer?
I am only asking because I had the exact same design in mind with a rotomax 50 cc but wondered if even the 80 was strong enough?

Thank you for providing all the information it has been a huge help and is much appreciated.