Spark plug differences

[Topol_86]

Didn't want to hi-jack another post i was reading, so here it is. Does anyone know the specific difference between Champion L77JC4 or QL77JC4? I simply ask because my manual said to run l77j4 plugs, which aren't available anymore, and the replacement is the l77jc4, which I now run. The plugs i replaced though were QL77JC4. Just wondering what the actual difference is. Thanks for any help.

Topol_86

 

[ezeke]

Re: Spark plug differences

http://forums.iboats.com/showpost.php?p=2621217&postcount=14

As to the availability of the L77JC4, you can find them at iboats, 50 at a time: http://www.iboats.com/mall/partfind...gd_poid=173481&gd_row=24&**********=289742085

They actually are very available.

 

[Vic.S]

Re: Spark plug differences

QL77JC4 are the same size and heat rating etc as L77JC4

The difference is that the "Q" plugs have inductive ( low resistance) interference suppression

Ordinary resistive suppressed plugs are not suitable for the OMC CDI ignition hence low resistance suppression.

If you do not need a suppressed plug then you can use L77JC4 but if you want a suppressed plug then its QL77JC4



The "Q" plugs are recommended for engines with VRO/OMS

The "C" in the number of the modern plugs indicates a "copper plus" design. A copper cored electrode AFAIK

 

[Topol_86]

Re: Spark plug differences

Thanks for the info, on a 1978 70hp Johnson I don't think I need the "q" series plugs, and ezeke, I know the L77JC4 plugs are widely available, it's the L77J4 plug that isn't available anymore that I was questioning. Thanks for the info though, If I can buy in bulk for plugs, I will

 

[Vic.S]

Re: Spark plug differences

That model has CDI ignition, not points so what I say about inductive and resistive suppression applies.
If you need, or want, to suppress radio interference then you need the Q series plugs.