Does the maths put you off Electronics? Check here

I thought the answer to the question of Life, the Universe, and Everything - was 42!

And another thing, if this is for an aeroplane those revs are no good at all. You'd need something like a 12" pitch prop to achieve anything like a flying speed of 70kph. It would be stalled at zero speed, I think!
Of course if it was for a boat it's an entirely different matter!

My Bullet motor develops 10.500 rpm's on a 4S. (750Kv = revs per volt).
I can't recall whether it has a 13 x 8 or a 14 x 6 prop on it.
It has a 150 amp speedo.
Without taking it to bits to read the labels, my Yellow Peril has a 1400 Kv motor, an 80 amp speedo, and a 3S turning a 10 x 6 prop.
Both of these will go vertical (upwards!) for a reasonable distance, but not unlimited.
The Excalibur missile with a 4S will go vertically out of sight in about five seconds. What the motor and speedo are, I have no idea, as they are pre-fitted and inaccessible without destructive dis-assembly.
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So - 4000 revs will taxi the model, but not much else! (You will probably find that your car engine ticks over at 2.500 rpm's).
Two x 3S in parallel is still 3S, but twice the capacity, so say its a 1000 lipo = 2000, but only 11.5 volts. Plus you have the added weight of plugs and wires - AND the possibility of a mis-match between the two 3S packs, so one will run down faster than the other, and you end up with a reversed-charge pack, which may well immolate itself!
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It is all well and good mathematically working out what is going on, but you REALLY need a Wattmeter, to see what is really happening, in the physical world!

You have some choices here, paint (Tippex) 2 stripes on the motor, hook up an ESC + a 3s battery and connect the motor. WoT and measure the revs. The other option is to mount the shaft in a pillar drill, switch on and measure the DC voltage between 2 wires. If you're running at 1,000rpm the voltage measured will be the kV of the motor. If not 1,000 you'll have to divide by the revs and multiply by 1,000

17x8 sounds very big for a 1.5metre wingspan but OK that prop will draw some serious power, especially at 12,000rpm! And that 5,000mAh isn't going to last long delivering 2,500watts! About 2 minutes if you're very lucky!