Carbon Buildup on Plugs

[wade]

Have a 20year old mariner 15 hp outboard. Starts and runs well but having problem with excessive carbon buildup on spark plugs after 10-15 hours running. If I don't pull the plugs and clean regularly I start to get misfires and lose power. Any clues where I should start to look to troubleshoot this problem

 

[JB]

Re: Carbon Buildup on Plugs

Wade, the most likely suspect is too much oil or incorrect oil in your fuel mix. If your mix is correct, check that you have the recommended plugs for your usage. Most makers recommend different plugs for extended low speed use than for extended high speed use. Other possibilities are a too-rich mixture, too-weak spark (incorrect point setting or failing electronic ignition module) and loss of compression.<br /><br />Hope this helps. Happy boating!<br />JB

 

[12Footer]

Re: Carbon Buildup on Plugs

My Force does this too. Carbon build-up "forces" me (get it?)to run cleaner through the engine every 30hours or so, or it starts fouling plugs.<br />I've been told that my engine is a "dirty design",which is why they dropped the whole line. Seems they couldn't upgrade them to EPA's more strict standards.<br />I understand Mariner met the same fate. But JB is right-on about the mix.And make sure it's a good grade of oil.<br /><br /><br /><br />------------------<br />I'm no expert, but I DID sleep at a Holiday Inn last night!

 

[12Footer]

Re: Carbon Buildup on Plugs

And > 90 Octane fuel.