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I have a 2001 Johnson 90 ocean pro outboard that has been making some racket in the top end of the engine. The mechanic, after trying several other options first, took the head off the clylinder and found no problem with the pistons other than excess carbon buildup. In the last three weeks prior to the head removal, there has been 2 cans of deep creep and 1 can of power tune run through the engine and there is still significant carbon deposits. I have been told that excess oil consumption can cause the carbon build up. I idle the motor alot when fishing which may be part of the problem. Is excess oil the culprit and if so can I disconnect the oil injection and go to a manual mix to help the problem? Any ideas or experience would really help. Thanks, Jeff [sad]
 

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I run my Merc 80 without the oil injection - too many single point failures in the system that will trash a powerhead before you can react. A low ash synthetic oil will help prolong plug life and cylinder deposits but they'll still need cleaning, especially if you run at low speeds for a long time. I keep several sets of spare plugs around and just replace them every few trips and clean up the old ones. Running at the proper temperature, keep the thermostat in, will help with plug and piston deposits. Also use a small dab of dielectric grease on the plug ends to ensure a good electrical connection to the plug wire. From what I hear Johnson has a good decarbonizing product but I've never tried it. I use Mercs Power Tune once a year, but only because I have a case of it. I haven't encountered a fuel additive product that does the same job a specialty decarbonizing product. They're a pain but they work. Nature of the beast for a 2-stroke. If you've got a strong spark and give it a good run occassionally you shouldn't have to decarb more than once a year, but it also depends on use. I run about 1500 statute miles (per GPS) a year.
 
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