Thread: "Decarb" Question

A decarb is VERY hard on plugs...eccspecially if you have alot of carbon come off the plugs can foul. Sometimes its okay...but if you have a two cylinder and you lose one plug...you stuck...better safe than sorry.

OK, Scrapper.........been hearing about de-decarb, so for the de-carb novice, what are some symptoms that signal a person that it's time to decarb? And do you have a step-by-step process?

Decarbing Your Engine- The Process-HOW AND WHY - iboats Boating Forums

The above link is the best way and explaination of decarbing I've seen. I will put it on our FAQ so its easier for folks to find.

There really are not alot of symptoms....its more of a preventative maintainence. Normally when you get symptoms its to late. It will improve you idle if you have much carbon buildup because carbon on pistons will change compression ratios a bit. Normally when you want to do a compression test and you see your numbers are out of the 10% difference range a good decarb will get them back in. Carbon also builds up on piston rings and can actually cause them to break...we call that build up coking. You will read about all this on the thread above. Some GREAT explainations there. If you have a johnson or any other white engine you will see alot of soot buildup around the lower unit vents and the exhaust relief ports on the midsection of the engine.

Fuel, lowgrade oil, too much oil, lugging, idling alot, to cool of a heat range plug...there are LOTS of reasons for carbon buildup. You could kind of think of it as "sludge" in your vehicle....although not the same thing...builds up just the same...some oils have more detergents/cleaners than others. Remember the oil commercial where they dump the sludge on the cars??

I would recommend it as described in the above thread once a year...probably before you put up in the winter...if you don't put up (winterize) do a good decarb, then run seafoam, carbon guard, ring free, or any of these in your fuel to prevent it.

Once last thing that it doesn't say in the thread...I like to take the plugs out and look in my engine. Turn it over by hand and look at the piston tops. It should not be black...if you see black...or little rough chunky areas of black...thats carbon. If its nice and clean, go ahead and do the decarb but you are in good shape. Carbon can still build up on the inside of heads where you can't see. I just like to look at the top of the pistons with a flashlight or LED and get an idea.

If you have any other questions please ask. We are here to help.

Thanks for the info, Scrapper. Good, simple, easy to understand stuff....