Posts: 202
Location: Angola, IN | Fisher: I don't think decarbonizing a 4-stroke is as important. But all combustion engine have a tendency to develop deposits in the combustion chamber. For a 4-stroke, I'd simply a bottle of Gumout Regane High Mileage or Techron Concentrate (both contain high amounts of PEA) for every 10 gallons of fuel in your tank every other or every 3rd tank to keep everything nice and clean.
It's real easy to get the wrong stuff, because these companies make so many products. And only a few contain any PEA. Here are the two I recommended above:
http://www.gumout.com/ourProducts/highMileageFSC.asp
http://www.techron.com/techron-concentrate-plus/Default.aspx
PEA is the only deposit cleaner that removes deposits without leaving any residue behind. It's the best stuff. Another product by Red Line, is called SI-1 and it also contains a massive dose of PEA.
http://www.redlineoil.com/product.aspx?product=60103
If you google "decarb outboard" you will find several methods of doing this.
Another way is to remove spark plugs and liberally spray Seafoam into the cylinders (they make aerosol cans of Seafoam now). Let it sit over night. And then add some to your fuel and burn out the carbon. You can actually use water to clean out carbon deposits as well. Never did it to an outboard yet, but if you've ever torn apart an engine after a head gasket failure, you'll see how clean those piston tops come with a little steam. I de-carbed my old Chevy truck one with water. Slowly poured 2 gallons of water down the intake (took me about 20 minutes) and my entire neighborhood had a thick white fog rolling through it!!! And it smelled just like a burnt firecracker!! 100% carbon being blown out the exhaust pipe. It got rid of my ping/pre-detonation immediately. But use this method at your own risk!! You could hydrolock your engine if you aren't careful.
One thing you'll notice when de-carbing a 2-stoke is, your idle and cold starts will be so much better. I have a 44 year old 115HP Johnson that use to never run at idle and took forever to get started when cold. Not any more.
The carbon closes up the transfer ports found in 2-strokes and prevents reed valves from opening and closing properly. It also freezes up rings by embedding in the ring lands on the pistons.
Edited by SteveHulbert 2/21/2013 2:07 PM
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