84 merc 115hp erratic spark all cylinders

[GHBART]

All spark plugs out and connected to a grounded wire.
Turn engine over and only some plugs spark.
The plugs that spark change from time to time
Sometimes only one sparks and some times more that one and not always the same ones.
Problem is not just on the plugs on one switch box
Oscilloscope observation of all flywheel signals look good.
I want to test by completely isolating the two switch boxes.
Can I disconnect the wire that connects the upper and lower switch boxes together that goes to the to the idle stabilizer (which is not connected)?
Can I disconnect the wires that are connected to the console switch and the tilt switch (which also ends up connecting the two switch boxes together)?
I want to eliminate any connection between the two switch boxes. This would be only to test for a spark and not for running the engine.
Thanks

 

[Laddies]

Re: 84 merc 115hp erratic spark all cylinders

Try disconnecting the 2 yellow wires from the rectifier and retest and next disconnect the bias wire between the boxes if that don't work we can give you a system test for the ign.