To watercool ESC or not?

Hi all,

I’m looking to put together my first e-foil build, leaning towards the Flipsky 65161 and 75200 ESC.

I’m only surfing waves (no flat water cruising) looking to create a “kicker” that will run for 10-15 secs to provide an extra bit of thrust (along with paddling) in order to catch waves further out from the break. I’ve looked around the forum and don’t see many people discussing using a foil drive like this, so if this is a dumb idea please let me know.

Here’s the ESC on Ali:

I notice that the 75200 comes in both water cooled and non-water cooled versions, what is the conventional wisdom with regard to ESC cooling? It would be my preference to not use water cooling (seems like a water pump is required? would a water reservoir also be required?) however I obviously don’t want to cook the ESC. Could I get away with the aluminium heat sink if I am only driving the motor for 10-15 secs every couple of minutes.


A lot is going to depend of the size of your board and foil. Waterstart is where you use the most current. If the board is 5ft+ with some volume you will be fine to use the non watercooled version for 10-15s, just fit it on an aluminium bar. Even better, if you use an aluminium mast just build you board so the VESC seat on an aluminium plate or in an aluminium enclosure in contact with the mast baseplate then you will have no issue even going for long run or using a small board.


There is a foil assist thread. I wouldn’t be using a big heavy 65161 for a minimalist foil assist setup, the smaller outrunners will be enough power. You shouldn’t need water cooling for the esc for a 10 sec low power boost like the foil drive, so long as the current rating of the esc is adequate.

Indeed, 65161 is too heavy. 63100 and a low pitch prop, so you don’t need much amp from the battery. With low amp you can choose a small battery, which is also good for your overall weight. Put the motor high on the mast so you don’t need folding props and there is no additional drag. One of the builders here has done this already


Great thanks for the advice, I thought that it might be possible to get away with an alu heatsink. I am currently on a 7ft board with plenty of volume so I shouldn’t have much trouble.

Cool thanks, I thought that the 65161 might be a bit overkill, however browsing the forums it seems like a common setup with the 75200 ESC, so I didn’t want to go with something too exotic for the first build.

WRT the 63100, I see that’s an outrunner, from what I’ve read outrunners require special preparation in order to be waterproof, such as replacing the bearings. I’ve done a cursory search of Aliex and it doesn’t look like they sell waterproof versions off the shelf?

If this is the case I’ll hunt around on the forums for outrunner waterproofing guides, but if anyone could point me in the right direction that would be great. How hard is it to waterproof an outrunner? I’ve got a small workshop available but don’t have a lot of time, so not sure if I should have a go at waterproofing, I’m a bit worried about screwing it up.

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Hi Marty,

different methods and opinions on how to waterproof but this thread is a good start. Direct drive outrunner with direct water cooling

I’ll be waterproofing one soon as well, haven’t done it before but doesn’t look like a very big job…


I could not follow that thread at all, it was all over the place :grinning:

Seems like the stator needs to be coated with something like epoxy, and the bearings need to be replaced with ceramic type.

I presume that if you get any part of this wrong you’ll blow the system at least as far as the ESC, and without an antispark, the battery too?

I still have to start on my first build, but I think you’re overthinking it. Put a 150amp circuit breaker on your electronics and nothing is going to burn or blow :). If you epoxied your motor and it still turns well, I don’t see any problems. If you coat too thick you won’t be able to assemble or turn your motor so you’ll notice immediatly.

My view: thin coat on the female part of the motor, thin coat on the male part and replace the bearings by stainless steel ones. Flush the motor after salt water use and see how long it goes :).

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Coating an outrunner is not really complicated, I just diped the stator (windings and iron part) in epoxy. For the bell I put some shrinking tube over the shaft (inside the bell) and put a 3d printed bottom part to cover the slots. You could also fill them with playdo. This way you get a closed „cup“. Pour in some epoxy, and turn it around to cover everything. Make sure the „drops“ that stay at the parts are not too big so there is still enough gap between stator and rotor. Otherwise sand it or use a lathe to remove excess epoxy. Although ceramic bearings work, they did not last that long for some people. Stainless steel work well. Last thing is to cut the shaft with a dremel as it sticks out on the wrong end. Cut it just after the circlip.


Alright, that sounds doable, thanks.

I was just browsing Aliexpress for the 63100 series outrunners recommended by Ackermann, and noticed this one:{"sku_id"%3A"12000021504083119"}

It’s claimed as being “battle hardened” which basically looks like the bell is already coated in epoxy, although it seems that this is to prevent damage for e skateboards, rather than a waterproofing measure. I might get this one and take a look at the job they have done coating the bell.

Hey couple more quick questions, when you say low pitch prop can you give me a rough indication of what sort of pitch this would be?

Also I notice that it’s possible to get a “sensored” version of the 63100, do you know if the sensor will still function once the motor is waterproofed?

I presume that this sensor would be connected to the ESC so it could be used for tuning?

One of the things I’m thinking of is just having a hardwired button on the board that once pressed will run the motor until it reaches a certain rpm and current draw (I should be able to work out when I’m planing) and then the motor auto shuts off so I don’t need a hand held throttle. Is this feasible? I’m familiar with generating PPM and PWM signals from an arduino, so I’m confident I can program a timed throttle signal, but I’m not sure if this functionality might be able to be implemented on the ESC side?


A very clever idea (basically an invention - it could probably be patented), easy to implement, go for it! But don’t forget to add some safety feature to shut down the motor immediately (leg lanyard, etc).

Well if you need the motor to assist wave foiling you probably will have a big foil. So you should think about the speed you need for take off, let’s assume 20km/h. So this is a speed you want to achieve. With a 190kv motor and like 12S you will have 7200 rpm on low voltage. Take a propeller speed calculator (google). With a 3inch prop you may get the desired speed and you will have not much amp need. You could probably go with a 12S5p pack (Q30) with maximum continious of 70 amps. Maybe less “P” also works. It’s hard to tell though, there may be some try and error trails necessary

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I do not have experience with sensored motors, but yes I think it get connected to the Vesc. The sensor is for sure electric or magnetic controlled, so the epoxy will not confuse it

Maybe for the throttle a button on the deck, at front? For efoil you need to have weight in the front, once you catch a wave you have to shift more to the back (this is what I have heard). This is the moment you release the button and motor will stop spinning. A magnetic switch on a leash to disconnect e.g. the receiver from power to have a little bit of safety

You can also run it sensorless, less cables to run up the mast.

6s Lipo is enough Power