Re: Johnson PO-15 Spark Plugs?

[Anonymous]

D6 is marked on the plug, but if you look in the Champion catalog a D6 is a stock number 506. D6 on the plug and Champion calls it a stock number 506. D9 is stock number 509. I use D6 plugs in my PO motors, which is the current closest plug to the Original R7. The D6 is slightly hotter than the R7. And the D9 is a little hotter than the D6. After running D6 plugs in your motor check the color and if they are very dark brown to black tips then try D9 plugs to get a medium brown colored tips.