3-inch FPV motor
GEPRC GR1408
A 15.2 g 1408 for 3-inch props on 4S; on GEPRC’s bench at 16 V on a GEPRC 3042 the 3750KV pulls 573 g per motor and the 4100KV 648 g.
- 3-inch quads
- 4S (rated 2S–4S)
- 3-inch props
The spin is an illustration: the model turns at 1/600 of the no-load speed, and it is a generic 1408 motor drawn from GEPRC’s published sizes, not its exact design. Thrust, current and power are GEPRC’s bench figures for the GEPRC 3042 prop at 16 V, read straight across between its throttle steps. Its data starts at 50% throttle.
- Max thrust
- 573 g
- GEPRC 3042 prop, 16 V
- Weight
- 15.2 g
- without wire; the same for every KV
- Peak current
- 18.1 A
- full throttle
- Max power
- 296 W
- full throttle
Plain links: we earn nothing from them.
What it pulls
GEPRC’s own bench test, one line per prop. Drag across the chart to move the throttle; the model above follows.
At 60% with the GEPRC 3042: 355 g of thrust, 9.5 A, 156 W, 2.28 g per watt.
On your quad
3.5 : 1
Thrust to weight at full throttle: four motors pull 2,292 g with the GEPRC 3042 at 16 V.
At 60% throttle they pull 1,420 g, 2.2 times the quad’s weight.
All-up weight is the quad ready to fly, with its battery and camera. The thrust is the maker’s static bench figure; in the air it is lower.
What you get
About 650 g on 4S
The 4100KV pulled 648 g at full throttle on a GEPRC 3042 at 16 V, drawing 21.64 A; the 3750KV pulled 573 g at 18.06 A.
Source: GEPRC data table
0.15 mm air gap
N52H arc magnets sit 0.15 mm from the stator, which GEPRC says gives more torque.
Source: GEPRC 3750KV page, GEPRC details image
Cooler running
GEPRC says the bell’s ventilation slots cut the temperature rise by 20% against similar motors; after 10 minutes at full throttle its motors read 62–73 °C.
Source: GEPRC data table, GEPRC details image
CW and CCW threads
The M5 prop adapter comes with either thread, so the props tighten as the motors spin.
Source: GEPRC 3750KV page, GEPRC drawing, GEPRC details image
What to pair it with
Our reading of GEPRC’s numbers, so your build matches what the motor was tested with.
- ESC
- GEPRC gives a max current of 22.3 A for 180 s; its tables peak at 21.64 A, for the 4100KV. (GEPRC spec image, GEPRC data table)
- Props
- 3-inch. GEPRC tested every KV on its own GEPRC 3042 three-blade. (GEPRC 3750KV page, GEPRC data table)
- Battery
- Rated 2S–4S; GEPRC says it is optimised for 4S and tested it at 16 V. (GEPRC 3750KV page, GEPRC data table)
- Frame
- Four M2 holes on a 12 mm circle. (GEPRC drawing)
Where to buy
- GEPRCthe maker’s store; 3750KV, out of stock when checked$14.89seen Oct 19, 2026Visit
- GEPRCthe maker’s store; 3500KV, out of stock when checked$14.89seen Oct 19, 2026Visit
- GEPRCthe maker’s store; 2500KV, $9.90 reduced from $14.89, out of stock when checked$9.90seen Oct 19, 2026Visit
Plain links, not affiliate links. Prices change; the store’s page has the current one.
Full specs
| Spec | Value | Source |
|---|---|---|
| KV | 3,750 rpm/V (also 2500KV, 3500KV and 4100KV) | GEPRC 3750KV page, GEPRC spec image |
| Stator | 14 × 8 mm (1408) | GEPRC 3750KV page |
| Configuration | 9N12P (9 stator slots, 12 magnet poles) | GEPRC 3750KV page, GEPRC spec image |
| Battery | 2S–4S LiPo (7.4–16.8 V) (every KV; GEPRC says it is optimised for 4S) | GEPRC 3750KV page, GEPRC 2500KV page, GEPRC spec image |
| Weight | 15.2 g (without wire; the same for every KV) | GEPRC 3750KV page, GEPRC spec image, GEPRC details image |
| Dimensions | φ18.2 × 31.5 mm overall; 18.5 mm from the base to the top of the bell, with 12 mm of shaft above it (the page text gives the height as 32 mm) | GEPRC spec image, GEPRC drawing |
| Shaft | 2 mm shaft with an M5 prop adapter, threaded CW or CCW, standing 12 mm above the bell with 8 mm of thread | GEPRC 3750KV page, GEPRC drawing, GEPRC details image |
| Mounting | 4 × M2 holes on a 12 mm circle | GEPRC drawing |
| Bell | CNC-machined 7075 aluminium | GEPRC 3750KV page, GEPRC details image |
| Magnets | N52H arc magnets, 0.15 mm from the stator | GEPRC 3750KV page, GEPRC details image |
| Bearings | NSK (Japan) | GEPRC 3750KV page, GEPRC details image |
| Internal resistance | 92 mΩ (3500KV 98 mΩ, 4100KV 86 mΩ) | GEPRC spec image |
| Max current | 22.3 A (for 180 s; GEPRC gives the same figure for every KV) | GEPRC 3750KV page, GEPRC spec image |
| Max continuous power | 222.3 W (for 180 s; GEPRC gives the same figure for every KV) | GEPRC spec image |
| Leads | 24 AWG, 100 mm, silicone, rated to 180 °C | GEPRC 3750KV page, GEPRC details image |
| In the box | An aluminium M5 flange lock nut, four screws and two clips (the page names only the nut; the screws and clips are from GEPRC’s box photo, which gives no sizes) | GEPRC 3750KV page, GEPRC box photo |
Bench data
Redrawn from GEPRC’s test reports. Thrust is static pull on a bench, more than you get in flight. Power is volts × amps; efficiency is thrust divided by power.
3500KV on 2S–4S, 16 V1 prop
| Prop | Throttle | Current (A) | Thrust (g) | Power (W) | Efficiency (g/W) |
|---|---|---|---|---|---|
| GEPRC 3042motor at 62 °C | 50% | 6.09 | 281 | 103.5 | 2.715 |
| 90% | 15.02 | 512 | 240.3 | 2.13 | |
| 100% | 15.81 | 547 | 259.1 | 2.111 |
Source: GEPRC data table
3750KV on 2S–4S, 16 V1 prop
| Prop | Throttle | Current (A) | Thrust (g) | Power (W) | Efficiency (g/W) |
|---|---|---|---|---|---|
| GEPRC 3042motor at 66 °C | 50% | 7.16 | 282 | 118.2 | 2.386 |
| 60% | 9.52 | 355 | 155.7 | 2.28 | |
| 70% | 13.54 | 465 | 221.3 | 2.101 | |
| 80% | 16.68 | 520 | 270.3 | 1.924 | |
| 90% | 17.02 | 549 | 286 | 1.92 | |
| 100% | 18.06 | 573 | 295.8 | 1.937 |
Source: GEPRC data table
4100KV on 2S–4S, 16 V1 prop
| Prop | Throttle | Current (A) | Thrust (g) | Power (W) | Efficiency (g/W) |
|---|---|---|---|---|---|
| GEPRC 3042motor at 73 °C | 50% | 9.04 | 329 | 147.8 | 2.226 |
| 60% | 10.9 | 414 | 169.2 | 2.447 | |
| 80% | 20.73 | 569 | 318 | 1.789 | |
| 90% | 19.83 | 572 | 333.1 | 1.717 | |
| 100% | 21.64 | 648 | 354.2 | 1.829 |
Source: GEPRC data table
Inside the motor
A brushless outrunner: the coils stand still in the middle and the magnets spin around them. From the top down:
- Bell. CNC-machined 7075 aluminium, with ventilation slots and a six-spoke top. (GEPRC 3750KV page, GEPRC details image, GEPRC top photo)
- Stator. 14 × 8 mm, 9N12P, wound with wire rated to 180 °C, 0.15 mm from N52H arc magnets. (GEPRC 3750KV page, GEPRC details image)
- Bearings. NSK bearings from Japan. (GEPRC 3750KV page, GEPRC details image)
How fast it spins
KV is the motor’s no-load speed per volt. With nothing on the shaft, the 3750KV version reaches about these speeds; a prop loads the motor and brings it down, typically to around 70–75% of these figures at full throttle.
| Battery | Volts | No-load rpm (KV × V) | Electrical frequency | ESC steps per second |
|---|---|---|---|---|
| 4S nominal | 14.8 | 55,500 | 5,550 Hz | 33,300 |
| 4S full | 16.8 | 63,000 | 6,300 Hz | 37,800 |
| 6S nominal | 22.2 | 83,250 | 8,325 Hz | 49,950 |
| 6S full | 25.2 | 94,500 | 9,450 Hz | 56,700 |
A 12-pole rotor has 6 pole pairs, so every turn of the shaft is 6 electrical cycles, and a six-step ESC switches the phases 36 times per turn.
About the 3D model
A generic outrunner drawn from GEPRC’s published sizes: the 14 × 8 mm stator, 18.2 mm bell, 18.5 mm height, 5 mm shaft, 12 mm mounting circle and 9 teeth and 12 magnets. Anything GEPRC doesn’t publish is typical for a motor this size, and the bell’s spoked top, the base and the inside are a generic design, not this motor’s. The colours are read off the maker’s product photos. There are no logos or markings: it is our drawing, not the maker’s.
Sources
- GEPRC: GEP-GR1408 3750kv Motor (product page, with the spec list). Retrieved Oct 19, 2026.
- GEPRC: GR1408 2500KV Motor (product page, with the same spec list). Retrieved Oct 19, 2026.
- GEPRC: GEP-GR1408 3500kv Motor (product page; its spec list is the 3750KV’s, its details tab says 3500kv). Retrieved Oct 19, 2026.
- GEPRC: GR1408 3500KV, 3750KV and 4100KV specifications (image on the product pages). Retrieved Oct 19, 2026.
- GEPRC: GR1408 3500KV, 3750KV and 4100KV motor data on a GEPRC 3042 at 16 V, 50–100% throttle (image on the product pages). Temperatures are after 10 minutes at full throttle.. Retrieved Oct 19, 2026.
- GEPRC: GR1408 design drawing (image on the product pages). Retrieved Oct 19, 2026.
- GEPRC: GR1408 details (7075 aluminium, 0.15 mm magnet gap, N52H arc magnets, NSK bearings, 180 °C silicone leads, CW/CCW threads; image on the product pages). Retrieved Oct 19, 2026.
- GEPRC: GR1408 product photo (first gallery image). Retrieved Oct 19, 2026.
- GEPRC: GR1408 from the side (gallery image). Retrieved Oct 19, 2026.
- GEPRC: GR1408 from above, showing the six-spoke top (gallery image). Retrieved Oct 19, 2026.
- GEPRC: GR1408 with its box, nut, screws and clips (gallery image). Retrieved Oct 19, 2026.
