from early 70s upward Merc was evolving to electronic ignition ex: with stator CDI ignition under control of a trigger coil ( no mechanical points) .
around mid 70 they had phase maker ignition a bit of a mix of CDI and points MAKING contacts to fire the points. Normal magnetos usually OPEN their contact surfaces to generate sparks but PHASE MAKER closes the points to fire.
here is a good read on Merc ignition by M.Mohat
https://wrcoutboards.org/wp-content/uploads/2021/02/The-Phase-Maker-CDI.pdf
https://wrcoutboards.org/wp-content/uploads/2021/02/Generator-Coils-Explained.pdf
Joining AOMCI has priviledges 🙂
