It got hot in my motor controller box yesterday after riding 30min. No major damage but the isolation of my 10 gauge wires close to the ESC suffered. Use 8 gauge motor wires and not the cheap audio ones like i did :).
.We are going with copper tubing up the mast, aluminum cooling blocks for the batteries, and then running water through the ESC. Also going to go with 8-10 AWG silicone wire that can handle 600 volts, and up to 105°C/221°F temp.
We have a similar setup like you, but we use a much larger aluminium plate to act as the heatsink. We also placed the esc inside a bulletproof ip 68 aluminium wiring box (it will handle a burning esc without trouble), and connected this with the aluminium plate by compression. We have also arranged the possibility to easily add a cooling pump if needed.
I talked to a friend of mine he told me that the if the esc is getting very hot, it might not be an ideal match between the motor/setup and esc, the heat is lost power due to bad efficiency. We got a new motor now (it says high efficiency…), will see if there are any improvements.
We use 10awg from the batteries to the esc and 12 awg through the mast, @pacificmeister do you use 8 and 10?
Sounds like a super nice setup @Nikolai! Am experimenting with props and ducts a lot to improve efficiency and reduce heat. Down the mast I had 8awg, currently I have 10awg. But crappy speaker cables, I will go back to 8 with high quality cables. What motor did you get? (we should probably start a motor thread)
@pacificmeister motor = tp-power 58mm with 440KV. The sss56 motor looks very similar, but the winding quality (and shaft) looks a bit better. Should definitly make a motor thread.
We used high quality silicon cables works ok with 12 awg. But I suppose larger wire through the mast will increase efficiency. Did you notice any difference between (12) 10 and 8 awg? The motor cables from the esc is 12 awg, so I guess that will be a bottle neck?
Unfortunately hard to tell a difference between the wires because other things also changed. You are right, the 12awg output from the ESC is not great, same on mine. But better just a short piece than the complete length, it adds up. We could also open up the ESCs and go straight in with bigger cables.
I’m prepared to open up my ESC and make it output 8/10 AWG instead of 12 AWG because we are making the ESC and motor work harder.
My Dad and I have also talked about the possibility of using an aluminum box (custom built), but I would want it to be padded or something so I don’t hurt myself if I crash into it! Haha
Awesome @tylerclark , go for it! I am sure you can epoxy the ESC watertight again. Post some pics on that process please. And be safe with that box 
After seeing your setup @pacificmeister, I am concerned with shrink tubing and anything similar like the ESC’s waterproofing. Will have to think that through!
My new build will all be 8awg wire through and through so avoid this and be well within safety and heat ranged. The power we draw high and scary to be honest. The ESC in my opinion should be 8awg, not the thin 12awg like seaking 130.
I created a water cooling nozzle on the ducked prop setup this weekend to test, and WOW its perfect!
water circulates up the 8ft tubing through ESC and out the ESC box into bay. IT only runs when the motor is running so no added electronics to go wrong, and the faster you are riding the more water gets pumped. It did keep my SEAKING 130A cool, though the 12awg wires where HOT, while my 8awg were stone cold/safe.
Been using the water cooling ports on the ESC and it runs luke warm. Bought a cheap pump from china and wired to the spare channel on the receiver. Now I can toggle it on and off from the remote. Ran an internal 1/4 tube up the mast.
Are you water cooling your ESC? Or just relying on the cooling through the aluminum plate it’s attached to?
No hoses for cooling right now. Am just relying on the aluminum plate which gets a pretty consistent water spray from the bottom when riding close to surface. I might start running a tube up the mast soon.
Ist’nt the esc waterproofed?
Why not building a small aluminium case where the esc fits inside below the box with the batteries and Receiver. The pressure from the mast will flood the box with the esc. Still need to add a small outflow like boats have on the side.
If it’s not waterproofed just a similar concept with water flowing through the esc. There should je the issue if a pump is necessary or not…
If you are using a pump this thing thing is pretty smart. It will start your pump when the ESC is above 40C and cut of once below. (not my idea originally, a clever Swedish guy showed us.
What a great product…and free shipping to germany 
Do you think a pump is necessary or not?
I simply use ram-water from the ducted prop wash to push water up the tube and cool the ESC, super easy, and the harder you run the motor the more water gets pumped through ESC. I do have a pump, but never installed as less electrics is better.
My first sharing 
ESC cooling is the main difficulties in my opinion
For my firsts tests I installed a water close loop directelly in the box (see picture)
it worked fine, but too heavy
After, I created an aluminium box, and put the ESC into the back of the board for separe the lipo (it’s pretty much the same idea that pacificmeister)
Is the plastic bottom of that ESC able to dissipate heat? Might be better to remove the water cooling top if you’re going for aluminum heat transfer.
