a little spark plug cross reference help . . .

[Expidia]

1999 mercury 25 hp 2 stroke.
My daughter went to the parts store to get two plugs for her outboard.
i looked up a mercury cross reference website and it call for champion as oem plug QL78YC.

They allso gave her two NGK's NKG BPR7HS (im guessing these are resistors but she has no radio anyaway) he alsomsaid they were a step hotter and said these were marine plugs shown in the book for this 25 hp.
So i used these.

The two worn plugs I took out were NKG BP-8H-N-10

Her mercury manual says NKG are the recommended plug QL78YC or resistor version BPZ8HN10

So is she ok running the NKG BPR7HS plugs?
For now... We are keeping the QL78YC as spares in her boats tool box.

 

[Fun Times]

The site linked below usually has a pretty big list of plugs that will come close to the correct fit and heat range with what seems like one variance of hot or cold that would work should you decide to go outside of the recommended number you found either in the manual, on the engine, in a parts guide or what you may have pulled out of the engine yourself. Just input one of the numbers then see what else comes up under it. On the lower left side of the page, you'll notice an area to input additional numbers if needed.

Putting in you champion number the NGK's you have would work ok on her engine.
http://www.sparkplug-crossreference.com/convert/CHAMP_PN/QL78YC

Looking up an engine that appears similar to hers without having the engine serial number, I see the parts catalog says to use:

15	816737 2	2	SPARK PLUG	(NGK #BP8H-N-10)
15	816837 2	2	SPARK PLUG	(NGK #BPZ8H-N-10) (CAN/BELG.)

But it's not uncommon for the manual to say something different than the parts catalog. As long as they are a close fit...you should be good.

 

[Expidia]

tHx fun times for that quick response. Since she lives a few towns away from me ill have her snap a pic of the sticker for the serial number and then ill check the link you gave me for the range of plugs that will work with her model.

 

[Texasmark]

Merc comes with NGK surface gap on most engines