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Ok, here goes.

I have a motor speed control module that I would like to use to power a 12v electric motor such as a moroso electric water pump drive kit would have.

Basically, it's a device that steplessly varies the voltage going to a 12V load. By turning a trimpot you can vary the speed of an electric fan, fuel pump or electric water pump.



Is it critical that the speed of the electric motor be controlled precisely by the RPM's, or are you just looking control that's "in the ballpark"?

If it's ballpark control, you could simply rig something up so that the trimpot you mention is turned based on your accelerator position. Generally speaking, the further you press the accelerator petal, the higher your RPM's will be. There is lag when you first press the petal, and your RPM's will not correspond to the petal position when going up or down hills, accelerating, decelerating, etc. But, petal position is dictating how much fuel and air is going into the engine, so it may be a better measure of how much cooling or fuel you need.

I'm guessing that it would be much easier to rig up a bracket and some mechanical connections so that your trimpot is controlled by accelerator position (at either the petal or the carb), rather than engineering and building an electrical circuit that would vary the voltage based on engine RPM. But, if you are looking for something more precise, this wouldn't work, and you would need to engineer a circuit.

If you do go this route, though, make sure that the trimpot would not be able to cause your accelerator to stick - there's been enough of that lately. Creating a "one way" mechanical connection to the trimpot, so that you only move the trimpot by pressing the accelerator down, and then have the trimpot moved back with a return spring (instead of having the accelerator mechanically move it back) would do the trick. That way, if the trimpot freezes, the accelerator will still return to idle.




This is what I would do!!!