Mercury 700 or is it really just a 70?

Serial# is 4716057.

Ran engine a while on the water then it shut off and would not start.

What I found today, when I disconnect the gnd wire on the #3 coil (which the gnd wire is gnd'd to the switchbox, the engine started just fine.

If I touch that same gnd wire back to the (-) term on the #3 coil, it immediately shuts off the engine.

I cannot ever recall seeing one do this? It's like the #3 coil gnd wire is acting like a kill switch.
Stator and trigger test good and so does switch box.

Just wanted to check in and see if some of the people who have been doing this for MANY years have seen this happen.

From the knoweldge I have, this is just a bad coil. Just can't explain how it's doing this. As long as the #3 coil gnd is disconnected the engine starts right up.

Does it run all all three cylinders with that wire disconnected? And what color is that wire? If it's black with a yellow tracer that's the kill wire.

Jeff

#3 cyl has a weak spark, of course having no gnd would cause that.
It's just a black wire for the gnd on #3 coil.

Right, b/y is kill wire..marine tech here too..

I just haven't seen one do this..I mean kill the whole engine?

I'm thinkng bad spark box. How about you?

Jeff

Are you referring to the switchbox?
The switchbox tested out fine.

It's just that #3 coil. Having the customer order a new one..It's just plain weird IMO.
I'm guessing no one has seen one do this or maybe someone who has just hasn't read this thread.

Have you tried swapping coils to see if ther problem chased itself to a new location? First thing I would have tried.

Jeff