Sorry! Ignition coil on a inboard mercruiser 170. Was basically looking for confirmation that it doesnt ground through mount but if it was that would mean there was an internal short of the coil which would be indicated by improper resistance readings of the coil.
Answered my own question i guess.
based on your question, you do not know how an ignition system works
first, a powered ignition is hot all the time, and the "trigger" simply pulses the ground prior to the cylinder coming up on TDC, and "breaks" or "opens" the connection to allow the coil field to collapse and create a large output on the secondary windings.
second, your motor came with points (or breaker points) type igntion. these area a mechanical switch that opens and closes with the cam lobes on the distributor shaft. they must be properly set and in-time
third, my guess is you have an ignition type issue and you dont know where to start
4th, if your coil is internally connected to the case, that means it was hit with a high enough current and voltage to pierce thru 3 layers of internal insulation (basically lightning would do it, or an arc flash from a 40,000 volt transformer)
5th, if you have ignition issues, service your points. that means file the points, clean the points, gap the points to .016", verify the dwell at 32 degrees, then start the motor and set timing.
