Mercury CDM 835084A1 Electrical diagram Mercury Force 90 Trigger and stator

[Beno]

hi all, Thought I would contribute today, I’m working on a 90hp Mercury with the CDM 835084A1 ignition.. not sure if CDM is a precursor to CDI or not but thats whats it called.

I couldn’t find this diagram anywhere on the internet, so I flowcharted it out and them powerpoint’d it and converted it to JPG and uploading it here .

this design is fairly simple, this is using a red stator 832075A21  and trigger 828302A1.. NO COMPUTER.    This seems like such a monumentally good design, but alas it must have not been a long term winner because EVERY design after this uses some combination of a $200-400 CDI box to run the spark.

see attached pic.

 

[billw]

I can’t remember, or did I ever really understand, why; but there was something about CDMs that relied on each other to work. I don’t see it in your diagram but there would sometimes be a situation where one cylinder had no spark but another CDM was causing it to happen. So the easiest way to trouble shoot it was to have a spare, known-good CDM and simply plug it in, replacing one CDM at a time, until you had spark on all cylinders. You’d test the charge and trigger voltage in the normal way but the CDMs themselves, you just replaced and checked until you found the right culprit.

Long live American manufacturing!

[Beno]

Well it’s just a guess and I can’t be sure but if you follow the green and white wire it would appear to me that the stator is charging all three coils at the same time using the same little charge Network..  (then the trigger systematically sends the timing signal to fire)

If one of the coils were to go bad for instance it started having a less ohms.. it would essentially ground out the stator?   And theoretically this would be the end of charge spark for all three cylinders.

Just a thought.

[Author]

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