# Need plug gap for 25 merc 2 cyl .....champion QL78YC



## richg99 (Nov 28, 2009)

I have searched the web to no avail. Any help appreciated. thanks Rich


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## Brett (Jul 16, 2008)

Your model in here?

http://www.dixiemarinesales.com/Spark_plug_Reference_Mercury.aspx


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## richg99 (Nov 28, 2009)

Yea, the model is in there..but...they only show NGK plugs. I have a cross-referenced Champion QL78YC. I may have to take it back and try to find a NGK. It really shouldn't be this hard to find a plug gap, though...should it? thanks for trying. Rich


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## Brett (Jul 16, 2008)

Same gap for both resistor and non-resistor plugs
what's shown should work fine for yours.
No real difference between plugs,
gap is to get the right spark in order to properly ignite fuel/air mix
Unless you have a gapless plug...

NGK BPR8HS - CHAMPION QL78YC Equivalent


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## richg99 (Nov 28, 2009)

OK Then, you are saying that, if the NGK shows a gap of .040 (which the chart shows) then I can use the same gap for a Champion branded plug??? thanks Rich


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## Brett (Jul 16, 2008)

yes


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## richg99 (Nov 28, 2009)

Thank you, as always.... Rich


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## Jared_Traina (Jul 26, 2010)

CHECK YOUR GAPPING! I called merc to ask them a gapping for NGK plugs on my 2002 9.9 Merc. They told me 35 thousandths. Tried that and the engine ran like crap. After looking more closely on a tiny little sticker on the block, I found that the gap should have 60 thousandths. Just a thought on checking. I have also had a big performance difference in other motors I have owned when switching from Champion to NGK.


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## Brett (Jul 16, 2008)

I like having the correct information when working on my outboards
which is the reason why I buy the Factory Service Manual when I buy an outboard.
Saves me time and money in the long run.

A recent post in this section listed a link to older manuals, for free.


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## richwalker71 (Feb 11, 2010)

I found my service manual (for this same motor) on E-bay for $7 on disk. Shipping included!


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## Peter2006 (Jul 23, 2009)

> I have searched the web to no avail.  Any help appreciated.  thanks Rich


Use NGK plugs instead and use what they say for a gap. usually .040 on those. Some are .035


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## richg99 (Nov 28, 2009)

Thanks, I did buy some of the NGK's and they were pre gapped to .040. Also received that gap info from another site. regards, Rich


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## jgregory01 (Nov 20, 2009)

Silly question perhaps. I have been running the L78YC in my 99 johnson for over a year now. That is what they had when I bought my boat used. My mechanic said they should have the QL78YC. He explained that they are longer and fire more into the cylinder. 

My question though is will there be a difference? Anything that I can notice. I never noticed a problem to begin with. Will there be a benifit?


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