Spark Plug Gap

[WizardIII]

I know I've seen this but can't find it now. Got an F block. Can anyone remind me of the plug gap with the Pertronix ignition module? Thanks, Steve

[Kelly]

I've got the same set up, and just this past week replaced all of mine. I set the gap at .025 on the NGKs p/n BR6S.

[WizardIII]

Yeah, that's what my service manual says for the Champion J6C's that I use. But I'm sure I read somewhere and confirmed with someone that with the Pertronix the gap should increase. Something like .035 or .040 but as usual I didn't write it down. Maybe it doesn't really matter.
Thanks for the reply.
Steve

[WizardIII]

OK, found a 3 year old post on the FG site where after installing the Pertronix unit the plugs were gapped at .040". Any thoughts on this?
Thanks,Steve

[Kelly]

Not sure, seems like a giant gap. I've ran mine at .025 with no issues until the place where I buy ethanol free fuel quit carrying mid-grade...which just happened within the past month. After fouling some plugs, I had to make some serious adjustments on the fuel/air mixture and idle control. Today it ran nearly flawless out on the sound for the first 5 hours but now I'm having charging issues.
Sorry, that was more than you were asking for.

[WizardIII]

Yeah, .040 looks like I gapped them with a coat hanger. However plugs are a little black so I think I'll try .030. I can still get ethanol free down here although it's premium grade for the racing guys. But I'll take it!
IMO, there's no such thing as TMI when it comes to boats & motors. Are you using zinc's up there? If so, what type and where do you mount?
Steve

[davriker]

The coil has more to do with the acceptable gap in the plugs than the fuel or the Pertronix. If you are still running a standard coil with a resistor wire, the plug gap needs to stay narrow, down around the 0.25 mark. A stronger coil can jump a wider gap, so if you have also upgraded to the high output coil, you won't see the benefits of the hotter coil unless you widen up the gap, ideally about 0.35 to 0.40.
Dave

[Kelly]

I've got a high-output coil, but keep the gap at .025 but that is primarily because my buddy that works on these all the time and built mine set it up that way. I've ran it for almost 2 yrs with no real issues, until the fuel changed.

BTW, no zincs. I leave the salt and drive to my lake and drop it in and run to our dock (after inspecting and rinsing first) to ensure a good flush under load happens.

[WizardIII]

Dave,
Thanks again for the coil info. I do have the resistance wire so believe it's a stock set up.

Kelly,
Looks like I should go back to original gap of .025. Is it ethanol gas that's fouling your plugs?

Steve