I'm not testing cranking voltage drop, the voltage drop was at the coil there was minimal voltage drop at the battery.
Your earlier statement indicated that on cranking the voltage at the couil dropped.
So just tested the power to the coil, it was 12.42 the same voltage as the battery but when I cranked the motor it dropped to 8 something volts.
As battery volts is supplied to the coil via the ignition circuit, it must reflect battery voltage... And battery voltage will nominally be between 9 volts and 10 volts when cranking.
If you are getting different volts at the battery and the coil when cranking, then you have some odd issue so i'd check the ignition circuit components that feed the volts to the coil (if thats the case)...
The battery may seem full according to your charger but it can still be faulty even when it cranks. Is the crank slow? Also, 8 volts at the battery on crank seems a little on the low side so i'd get the battery load tested as well as looking at the coil resistance and lean resistance among other things mentioned..