Sooty plugs:

[Aaron B]

Hi guys,

I hope your all having a super 4th! I'm messing around with my boat (which counts as a holiday to me) and I pulled my somewhat freshly installed sparkplugs and found 3 sooty plugs, and one fairly clean plug. I'm attaching a photo so you can see it yourself. I know that plugs will become fouled over time, but my issue is that I installed these plugs in early April, and I'd say I have put maybe 10-15 hours on them at the most. Also note that #2 is not nearly as fouled as the rest.

Anyways, just wondering what to read into this. Have a great holiday!

Aaron

[Mo]

Hi Aaron,

A couple of things come to mind.

a. I am wondering if you notice a sheen on the water near your exhaust. This could be an indication of the carb set too rich. You could try backing the mixture screw off 1/4 turn and see what happens.

b. Are you using oil. Possibility of some oil getting by the rings and fouling the plugs.

I am thinking a. as the cause. Clean up the plugs and put them back in. Then screw in the mixture screw all the way and then back it off 1 1/4 turns. At that point I easy it back just a bit more with the engine running (hard to say unless hearing the engine)....maybe another 1/4 turn. You will notice a change but don't back it off too much.

Happy 4th of July.

Once done that ensure you let it run a couple of minutes after starting cold just to warm it up good. When running rich they don't care about being warm or not, however when we lean them out they need to warm up a bit....that's what I do anyway...but I'm in a colder area than you.

[Aaron B]

There is a slick on the water

Hi Maurice,

Thanks for the insight. I did notice a bit of a slick on the water, so I'll be backing the mixture screw off a bit. I'll report my findings. I'm not sure exactly how it should sound at that point, so I'll do my best to describe it.

As for oil, I use a 10w-30, as well as the recommended amount of MMO in the fuel itself, maybe that could help soot the plugs also?

Hope you had a super 4th!

[Mo]

Hi Aaron,

The MMO will put a bit of carbon on them also. What you could try is running with a hotter plug. They create a little more heat in the combustion chamber and it is a little cleaner as a result.

You are on the right track to make a minor adjustment as you described and continue with the plugs you have for now.