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.

 

[BruceAML]

Re: yamaha pro 50 spark problem

Try running the motor with the cover removed. Do it early in the morning when it is dark and you should be able to clearly see where the spark is coming from. Do you have the Yamaha factory manual? It will show you the correct routing of the various wiring.

 

[rodbolt]

Re: yamaha pro 50 spark problem

trust me, you dont have a plug wire issue.
you have an issue with the white wire in the harness.
the white wire is kill circuit and its trying to short to ground due to bad insulation.
that wire has about 150 volts when the engine is running.
find the chafed spot in the white wire.

 

[pancakes]

Re: yamaha pro 50 spark problem

can't seem to locate that white wire. which harness is it in?

trust me, you dont have a plug wire issue.
you have an issue with the white wire in the harness.
the white wire is kill circuit and its trying to short to ground due to bad insulation.
that wire has about 150 volts when the engine is running.
find the chafed spot in the white wire.

 

[rodbolt]

Re: yamaha pro 50 spark problem

its in the main 10 pin harness, but your issues is going to be in the control box someplace. either its chafed or the ground is loose.
but as it shorts its also trying to kill the ign circuit.

 

[pancakes]

Re: yamaha pro 50 spark problem

i'll give it a whirl. thanks, so much.