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.
12.42 is not that great, put the battery on charge, a healthy battery is around 13.5v.
Open circuit voltage of a 90% charged battery will be 2.1 volts per cell, or 12.6 volts, see
here.
13.5 volts is when the battery is full and the engine is running with thealternator in float charge mode, that is, no real load on the battery or alternator.
As op stated, 12.42v was with engine off which indicates the battery does need a charge. The crank voltage seems to be a little low at 8v so I’d charge the battery fully and get a load test on it to verify it’s good…
In any case, spark strength relates to coil design, lead resistance and earthing so all aspects should be checked.
Is primary and secondary coil resistance within spec?
Is spark plug lead resistance within spec?
Is engine earth good (no resistance)?
Is earth on the switching side of the coil good (not sure how the spark is controlled on crank but the circuit that does this needs good earth)?
Are the spark plugs new?
Many ignition systems have specs on what gap can be jumped by the spark and can be tested using a spark tester (wind out to open gap type tester)… Spark should be strong and blue at specified gap…