Here is an application that is truly off the shelf.
There are several cordless drill manufacturers that make a drill and transmission that can be used with subs that have a large prop of high pitch.
Makita and Dewalt,those 2 have models that the motor and transmission are mounted together instead of the outer casing holding them together.
Makita model number 6313D
Why would I use such a drive?
Well for one thing I wanted an efecient motor that would not consume a lot of juice and that would last a long time.Readaly avaialable parts.
Also safe for the radio ,on one sub no need to ser press the RIF.
These motors are made specifically for high efficiency and torque as well as speed and yet will not overheat.
Some have dual ball bearings ,replaceable carbon brushes and rare earth magnets.
They also are made to start rotation with a low voltage input.
Also virtually no maintenance just check the brushes once in a while.
Since there are so many types I have not measured the amps but in general its pretty low.
The next advantage is that the trany usually a planetary 2 or 3 speed unit with up to 5 planetary gears made form nylon or metal and greased sealed in.
Some have ball bearings and thrust bearings made for some serious service!
In my application I found that the high speed gear setting gave the speed and torque required for the 2 types of props I run ,one is a 5.5 inch monster ,7 bladed weed cutter.It has a moderate pitch.
Its used on the Robbe U-31 and I get at a normal walking speed a 2 hour run time with 2 8 amp hour batteries with ser facing and diving several times.
The other drive is in the 5 ft Alfa it has a Makita all bearingized unit,it cost more about 100.00$ for the hole drive but it will last for many years.
The one pictured is the Makita ,this one was in a pod that developed a leak,was wet for months and yet is still fully serviceable!
The Alfa also gets about the same run time.
If you want very slow ,smooth operation and the power to turn large diameter and high pitch props that will give you plenty of power and I mean a lot of thrust without overheating or straining the drive than drill motors and there drives are the ticket.
Selectable gear ranges,built in clutch,I did not mention that,the clutch is a great feature and has saved my drive many times,just set the adjuster to where you would feel is best and if your prop gets fouled in a branch or fishing line the clutch will make a clicking sound that will alert you and save the drive line or even prevent the ESC from damage.
Regular ESCs can be used but at least a 30 amp or above would be recommended.
To mount the drive I used a metal conduit clamp on a flat sheet of metal or equipment tray,bolted in place with a water cooling coil and rubber sheet to make the grip.
On the U-31 it was mounted inside of the frame where the motor is normally mounted ,just removed one of the cross beams and secured the unit with 4 screws at the points showed in the picture.
To attach the drive shaft ,the screw that holds the chuck in place is turned down or ground to remove the head and that leaves a 3/16 stud that can be used with a standard U joint or adapter then to any size shaft you might have .I use 3/16 in on mine.
Be sure to flatten the set screw points on the shaft as there is a lot of torque.
When you get the drive you will have to secure the gear shift lever in the 2nd gear position and insert a screw into the clutch adjuster ring if not the balls will fall out,I can give more details about this proceedure.It is not necessary to order the clutch adjuster knob,that is the bell shaped plastic part that has all the numbers on it.
I water cool all of my subs to insure that the motor will run cool and now with the Telemetry system I can see the benefits in real time.
I ran a regular can motor that I use 550 RH with water cooling for a normal run and prop on a Red Shark .The temp went up to 99 F .
I then ran the same unit without the water cooling system working ,the temp went up to 118 F.
A noticeable lesser run time of about 20 min.
Water cooling is a great benefit for my subs and is highly recommended and is easy to build into your system in most cases.
A gear pump is driven by the main shaft or motor shaft to circulate a water antifreeze mix in a sealed loop to the out side wet cooling coil then back again.
Virtually no maintenance and simple.
On the U-31 the motor temp gets to 99 F at normal cruise speed ,walking speed not bad for a sub that has such a blunt bow and weighs in at 40 lbs.
Also there are cheaper drill drives that are smaller but don't have the 2 speed trany and will not turn fast enough.
The RPM of the above drives is 1400 at 12 vdc and is plenty of power for any large sub.
If you like I can set one up for you,ready to be installed, water cooled or not,for a small fee.
Dave Amur Sub Yard
To get the drill drives go to your local power tool repair shop or online at
And the Dewalt
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