Are you using 2.4GHz radio? This behaviour could be due to the failsafe setting, often this is where the throttle was when you bound the receiver. Try rebinding with the throttle stick set to motor off. Older 40MHz and 27MHz sets would not do this as they had no failsafe and the receiver stopped sending the signal to the esc when the radio signal was lost, this normally stopped power to the motor.
It is 2.4GHz, yes. Binding seems automatic, there's nothing in the intructions about it, only the programming mode. The programming options don't includle anything about failsafe power level either :(.
Sounds like it could be a car esc, these often have a brake function when you first reverse. then when you center the throttle and reverse again the motor will reverse. Do you have programming instrructions for the esc? You may be able to remove the brake function and have only forward, stop and reverse.
With electric motors driving air propellers you must always be careful to keep fingers out of the propeller arc. While it may not go through bone it will remove a finger tip if not careful. As long as power is being applied the motor is trying to turn so can continue to cut as long as your flesh is present As long as the battery is connected keep clear of the propeller it is live. Even if the throttle stick is at neutral it only needs the transmitter to be dropped or knocked for the motor to start.
Jim
No option for changing brake in the instuctions (k075B). It is advertised in eBay as suitable for boats, but I guess that doesn't mean much... That's not exactly the behaviour of my ESC: From forward, if I move the throttle (not suddenly) all the way down, the ESC simply removes motor power, without brake. To actually engage reverse, I need to leave the throttle in neutral for a second, then move it down.
I don't know anything about RC or electronics, but I find this a bit strange. I guess I should add that I'm buying components as cheap as I can find :S.
Anyway, with a bit of care the brake is not activated, so it may be ok.
About the propeller. I'll have to add a structure around the propeller for safety, as the goal behind building the airboat is to play with my 4 year old! (Plus I'm clumsy enough).