I just read your old post. The problem sounds more like a stator. Do you have a manual and a multimeter? A bad highspeed coil (blue wires) in the stator will cause those symptoms. There is a test you can do to check the high speed coil on the stator . . . MJ knows all about this :)
A bad switch box will cause you to lose spark on on side or the other (usually the whole side). You can check with a spark tester. If you don't have spark on (or one plug) try swapping switchboxes and retest. If the spark comes back it's that switchbox you just swapped out . . . otherwise it's not.
Spares - Is there a mercury bulliten about AGM and Gel batteries causing Merc stators to crap out? I read this post a while back and I've never had a stator fail until this year until I swapped the batteries out with fancy AGM's.
http://continuouswave.com/ubb/Forum6/HTML/000916.html