Don – Thanks for the good description of the system, and yes – what I called driver coil is the charge coil. I have a Clymer manual but it’s vague on some items. Reading it a bit, they do have resistance readings. FYI: they are saying that sensor coil should be 30 to 50 ohms. The charge coils prior to 1985 should be 500-600 ohms, but 400 to 550 ohms on 1973 to 1982 electric start models, and 550-600 ohms after 1984. All reading should be done cold.
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I wish there were ohmmeter tests for the power pack like the mid to late 1980s Mercurys have – I’ve had good success troubleshooting a couple of those with a procedure someone on this board gave me a couple years ago.
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My peak reading voltage test adapter should be here within a week and then I’ll start troubleshooting. If need be, I’ll haul out a functional 15 Hp I have of the same era and compare some readings. All this discussion has made me curious now as to what the waveforms look like at various terminals of the power pack, etc. I may take my oscilloscope out to the garage and do some looking on a running motor. My O-scope is no good for troubleshooting a dead motor because it is not a "storage" scope so I won’t be able to see one or two pulses as I pull it over. I can also swap parts between the 15 and the dead 9.9 as a way of troubleshooting, but I try to avoid doing that because it’s more work, and I run the risk of maybe killing a powerpack if there is something wrong with the bad motor that’s killing powerpacks – like the spark voltage somehow getting into it.
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I’d much rather troubleshoot the old magneto ignitions any day!
Thanks again Don