White gunk on spark plug, what is it?

[BrianH]

Performing my first ever break in maintenance on a 115 Yamaha outboard. The third spark plug I removed had a bunch of white gunk on it. It is kind of grease like. Any ideas what it is? I didn't notice any on the previous two so I am wondering why/what this is on the third. Here's a pic:


Brian (playing mechanic on Sunday afternoon) H.

[STGRule]

It sure looks like electrical grease. Don't know why it wasn't on the others.

[1pump]

Dielectric grease, aka tune-up lube. Keeps the plug boots from sticking to the plugs and tearing in half.
Looks like somebody got carried away with it. You don't need more than a light coating on the inside of the boot.

[BrianH]

Thanks guys. I suspected some kind of electrical conductor, but I got suspicous when it was only on sparkplugs 3 and 4.

I love iFish!