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Hello Jason here,
Auto coils and marine coils are not always internchangable. That being said, disconnect the gray wire at the coil and let me know if spark returns or not.
Remove them both
Could be... We'll go step by step to figure it out.
What does the voltage read on the purple wire on the coil with the engine cranking over?
Okay that's a little low. Get some scrap wire and make up a jumper wire with alligator clips on each end. Clip one end to battery positive, clip the other end to coil positive. This will bring the coils voltage closer to 12. Let me know if it starts with the jumper in place.
No, leave them off for now
What is the voltage at the battery reading with the engine cranking over?
Is this thunderbolt 4 or thunderbolt 5?
Okay let me know what happens.
Please do not forget to come back and rate my help if you end up getting it figured out.
Thanks again and good luck!