Propulsion System - Motors, Gears, etc


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.


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.


How are people connecting the ESC to the motor? Just soldering wire to each? I can’t seem to find the plug ins for them.


this 5mm :

or bigger:


Ah ha, thanks a lot!


Hi PacificMeister

I need some help here. I have the 360kv motor, but I am using the 3:1 gear reduction with these components.

4:1 Gear Reduction ( )

However, I am not getting enough thrust to get me moving.

Can you advise?


shaft coupler or gearwheel spinning on itself?


I have the motor connected to the input of the planetary gear and the shaft of the gear on a coupler connected to the propeller shaft. So I guess it is spinning on itself which requires 3 rotations from the motor to turn 1 rotation on the shaft of the gearhead. Just as the Parker gearhead setup (

My parker gearhead is 4:1 ratio. Did I connect the motor incorrectly? Should I couple the shaft of the motor to the shaft of the gearhead?


sorry i wanted to said that the shaft of the gear might turn inside the coupler (or the propeller shaft) when torque is applied on it, the coupler doesn’t hold the shafts together hard enough , so the propeller is spinning but under load the speed of the gearshaft is not the same any more then the propeller: no rpm, no thrust

take off the shaft is look if there is any friction mark inside the coupler (or on the motor shaft…) , maybe…

there is a all off coupler issue, but in your case, maybe and i don’t know how the parker gearbox is, since you have 3:1 gear there is more torque apply on the motor shaft, so check if the motor shaft connector to the gearbox is strong enough to keep the rpm (and may be use green blue or red loctite on the clamp)


Hi @MauiMan, can it be that too are only running 6S? Hard to see in the video but it looked like your batteries were in parallel. That would explain the low rpm. Seems way slow. Also try the other duckt, v2, the one you printed has a lot of drag. Looks good orherwise. Nice blue power button :slight_smile:. Are you on Maui?


Yes! On video looks more 6s 44a then 12s 22a


Is this the duct that you mean? I don’t see a v2 on the main post, but I may also want to reprint my duct.


Below. Not the seal mount. The improved duckt. I might have not exported STLs. Will check. You need to print matching props too, slightly larger.


My bad, I did a bad job circling the file in the screenshot. I meant the duckt, which is right below SealMount REV2


@pacificmeister I am connected in series for 12s. I am not sure if my config is good. Would a 360KV work with 4:1 Parker gearhead?

I think @Alexandre was correct in the slipping of the gearhead so I am slipping and not getting the maximum rpm.

@philippe I attached the photo of the velcro I used.


Aloha PacMeister! Would you mind sharing the link to the V2 Duckt? I cannot locate it.

Mahalo :sunglasses:


i glad you find the problem, so you are changing the gearbox and the motor as well? the motor is ok?