What are A and B leads on ECU?

On the ECU for my P60 there is a long text on a sticker which basically says if there is a problem disconect lead A from B to get the motor home in an emergency , this is aided with a diagram. Which leads are A and B? Is it the main loom plug that connects near the throttle linkage from the boat or one of the multitude of other wires coming from the ecu area as there seems to be plenty to chose from.
I can not find any mention of A and B in my manuals,

Thanks

[boats.net]

Not all ECU's have that lead but it bypasses the computer and sets engine to a fixed timming. It is usually a yellow wire thats just looped with a connector in it.