"Michael, the inline 6 marine
"Michael, the inline 6 marine and auto's engage the same but the auto's as mentioned aren't safe, I think the mechanical advance on the older ones are the same, like mentioned the vacuum advance would need to be removed ( easy ) but, still not safe.
Alternatives:
1. New.. from Sierra Marine and others like Pertronix ( they sell complete new units with their electronic ignition installed )
2. Used from many wholesale marine places, can even get a 2.5L/3.0L inline 4 cylinder and remove/replace the main shaft and use yours depending on the wear on the shaft. (did this myself recently as I broke the mounting flange on my original one)
3. the problem could be just a cap and rotor change, honestly I would install a pertronix ignition kit purchased from carshopinc.com or ebay. the Sierra Marine and Napa ones are the same but double the $$$.. Also get yourself a new set of marine wires and some new plugs...
ps.. my engine is from a '74 Nova.. (partly)"