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Nov 26, 2013, 09:43 AM
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Are brushless motors waterproof?


I have read on many forums that brushless motors can run under water. They just need to be rinsed after each use with fresh water.

Could you guys please express your opinions on this as I am building an underwater quadcopter?

Thanks a lot!

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Nov 26, 2013, 11:56 AM
"day ain't over yet-"
der kapitan's Avatar
All motors, brushed or brushless can run underwater. The problem lies with the speed controllers, which can't---.
Nov 26, 2013, 12:03 PM
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No problem as far as the motor goes, the one on the back of my outboard tunnel hull race boat gets soaked every time it runs, just load it full or WD-40 at the end of the day then put a drop of light machine oil on the bearings.
Mine is an inrunner, a buddy has an outrunner on the back of his, no problems either way.
I do replace the bearings every winter, easy job plus you can get better bearings than most motors come with stock.
Nov 26, 2013, 12:53 PM
Registered User
In fresh water, not a huge problem, as said, make sure that the water is displaced with oil at the end of the day. In salt water, great care must be taken to ensure that nothing live to the electrics can contact the water. All insulation must be watertight or electrolytic corrosion will happen surprisingly quickly. Then there is the possible problem of silt getting where it shouldn't and acting as an abrasive paste.
If its going to "fly" in, say, a swimming pool the only problems center on the minerals in the water - treat it like it was clean sea water.
Nov 27, 2013, 05:49 AM
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DDG 51's Avatar
On last submarine meeting in Neulengbach-Austria, was a lot of subs with outrunners placed directly in the water. All of them was working great, no smallest problems It needs just drop of oil before running ..But In salt water... I do not know, if it is good idea. Mabye just cheap motor for one season
Nov 27, 2013, 07:36 AM
Registered User
Thinking again - don't forget, radio doesn't work sub surface in salt water, 2.4GHz doesn't work under water at all, so a submerged quadracopter would either need to be autonomous or have some other means of control.
Nov 27, 2013, 08:45 AM
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DDG 51's Avatar
sure, 2,4 will not work, need use 72, 40, 41, 35 MHz frekvency. And waterproof electronic, connectors ,EVERYTHING
Nov 27, 2013, 12:24 PM
Registered User
Most electronics and motors will run under FRESH water and if dried out properly will function afterwards. Motors do not to run under water at speed because the winds of wire on a DC motor can become loose and rub the protective varnish coating off the magnetic wire causing a dead short.
SALT water is just a plain NO-NO!!! The corrosive nature of salt water will eat metal, solder, copper and mostly anything it comes in contact with. Even when washed out very good with fresh water, any salt water left in the winding of the motor will eventually destroy the motor.
Nov 27, 2013, 02:39 PM
r/c ships and workboats
Should also mention any water that is treated with a chemacle such as chlorine. Fresh water is just that--nothing added ( well at least intentionally).
Dec 01, 2013, 09:22 AM
Card Carrying Old Fart
Rickochet's Avatar
I have seen postings in the Seaplane forum people using something called CorrosionX sprayed on all motors and electronic gear except for servos.
Dec 02, 2013, 12:18 PM
Resistance is futile
circuitfxr's Avatar
I wonder if using Rustoleum's NEVER WET would protect the parts AND allow running in salt water. Something to research I guess.
Apr 04, 2018, 08:52 AM
Registered User
New to this forum.... was wondering if conformal silicone coating could be used on brushless motors to help prevent corrosion when used in fresh/salt water? Was thinking of dipping in the coating, then keeping the bell housing rotating slowly until it dries? Would love to hear thoughts and ideas.
Apr 04, 2018, 10:19 AM
Where's Pamela?
patmat2350's Avatar
Should work, but even better if the motor can be disassembled first, taking the bearings out of the mess.
If the bearings are oil-impregnated sintered bronze, they should be fine uncoated. Ball bearings, consider them expendable!

Note that magnet wire (your windings) are insulated with a varnish-like material... and it is normal that this coating has gaps. No prob if a gap is adjacent to normal coated wire in the windings. But if exposed to water, especially salt water, you WILL get wire corrosion over time at these gaps. The conformal coating should help a lot.

Other parts, I wouldn't worry about... exposed steel/stainless steel shaft, meh. Aluminum bell? Meh. Magnets? Not sure if they'll corrode at all, just don't want any surface corrosion to close up the air gap...
Apr 04, 2018, 05:03 PM
Latitudes vs Attitudes
Bob Gaito's Avatar
That never wet stuff is amazing! It will keep your cellphone operational under water-I'm sure it will allow you to run any motor underwater and if your ballsy enough probably the speed controller and the radio too!
Apr 04, 2018, 05:19 PM
Boats on the brain!!
green-boat's Avatar
I'd say not "waterproof" but they can be run underwater.

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