Propulsion System - Motors, Gears, etc


Yeah i was afraid of that… some 6-8S videos got me almost turned on, especially virus 8S setup.
Cmon belt drive, u can do it!


Lol. Just got new belts today and put it together again. Fingers crossed.


I’ve ordered and am looking at something similar,

8-10kw water cooled outrunners 83110

85mm ducted props


Hi all, what is the predicted torque needed!? I can’t rememeber the number ! 7 Newton’s ?
9 Newton’s ?

@pacificmeister what was your top end stats? Torque ? RPM ?

Thanks , David.


@DavidC I don’t have measured stats. My unloaded theoretical prop RPM is 5k with my 500kv, 5:1 50V setup.


My buddy finished as a mechnical engineer and his memory is a bit furry but he remembers some theoretical crap from the student days. For the rough aproximation it went 30 x P/Pi x n where P is power in W and n is rpm. Interesting numbers if u calculate motor on lets say 100A and 50V (500 kv) it would be :

30 x 5000 / 3.14 x 25000= 1.91 N

On 5:1 that would be 9,55 N. Not 2 far eh? :smiley:


no worries mate, ive ordered 2 water-cooled 10kw brushless outrunners 83110 150kv predicted 7.5newtons and a dual 300A watercooled esc. i am going to run them as a twin 88mm impeller system.

88mm because the 90mm tube will have a 2mm wall.

what you think? im building the drive system for my foil board but want to make it adaptable for another secret project along with a drive system for stuff like paddle-boards, surfboards, kayaks

all in the motor esc and wiring was similar in price to a gearbox setup .

when we get our board design tested we are then going to do a roto moulded low poly board.
low poly-cheap and cheerful




Sounds like a good plan. Quite a monster torpedo and I hope your 88mm impeller works at that relatively slow motor speed. But you will have enough power with these 20kW and you should be able to handle that extra drag. Keep us posted.


haha the plan is to run them soft. we want the power for another project.