yamaha pro 50 spark problem

[pancakes]

i have a '94 Yamaha Pro50 with an intermittent spark problem. while underway, the motor cut's down to 2 or maybe even 1 cyl. and as it does this, sends a spark through the throttle assembly, zapping my hand. i know that the spark is arcing somewhere under the cowling because i can hear it but can't reproduce the problem on land and, therefore, can't localize the spot of arcing. can anybody tell me the most likely place to start? if this were a car, i'd just replace the plug wires but the wires are not sold separate from the coils themselves which cost 75.00 a piece! trying to avoid that. any ideas?

thanks in advance.