Just replaced stator had 1 low voltage , and another winding at half.Damaged switch box.Both replaced , tested perfect to my factory Merc mechanic( 2nd mechanic in 3 months) .Got less than 1 hour on it before I lost 1-2 cylinders.Made it back to ramp , got home had fire at all 3 plugs.Same crap I had before I replaced the stator, switch box/ oh, and did I say I also had previously replaced all 3 coils.Whats left???? Checked wires ,battery......just put the call into my paid Merc mechanic I am going broke and no0 boat !Any suggestions?????

Figures after working on ignition , turns out alcohol in fuel had damaged two needles in carbs and 3rd carb was cracked, will see if it runs ok when I replace these parts.
Buck

if your getting sparks and its running sometimes
sounds like you may have a pinhole in your fuel lines somewhere, maybe it got pinched while some one was working on it.
pressure test your fuel lines.

I know just how you feel. I have a 1987 Merc. 70, tested and replaced the trigger and stator...still have no fire! Do you know if the switchbox can be tested off the motor?