The ESC above mentioned does not work with Futaba 7c & receiver R617 FS. Electric motor does not run.
However, if i replace that ESC with another of 20A BEC, everything works well.
Not finished, now, if i replace the Futaba 7c with the Tunegy 9X, plus receiver 9X8C, the 50A Hobby King ESC works.
Am I missing some critical set up on futaba 7C? Find nothing on the Futaba's manual.
The 40A ESC says it is programable.
Any idea of what is going on here?

Thanks, for any help.

Is the throttle reversed on the Futaba? Is there an arming procedure that you're missing?

The throtlle was indeed in reverse, as it is normal on Futaba's radios.
I've reversed it already.
Fixed problem by performing an ESC calibration, according to the ESC manual.
I've learned that a calibration is necessary when you connect the ESC for the first time.

Thank you Jester_1

I'm glad it was something simple. That's the stuff that is so hard to figure out.

You are right, hard to figure out, especially for beginers like me.
I spent one entire week searching and thinking about this, until I looked into ESC manual.
cheers.