9.8 mercury lose spark at idle

[bmuise6050]

one the lake above idle runs good ,but u go to idle an after a few minutes one plug goes dead , i took it home an put it in bucket of water hooked up a grounded test plug an after it idles for a few minutes no spark to upper plug bring throttle up an spark returns . an thoughts on it would b helpfull thanks

 

[3gsdad]

Re: 9.8 mercury lose spark at idle

Switch the coils around. if the plug that is giving you trouble runs fine and the other starts to miss then you know its a coil. I had to replace one on my 9.8.
I was told while messing with mine it could also be the switch box. I don't know how to test that, never had to. The new coil had it running perfect.
You can also switch the plug wires around to see if it may be one of them. They pull right off the coils.