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Decarbing faq

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  • Decarbing faq

    Since this pops up every other day on some board, try this method, I picked it up on another board and have been using it for awhile now,works great.
    Tip for the Week
    Do-It-Yourself Engine Tip; A Simple and Cost Effective Way to De-Carbon an Outboard
    By Capt. Bob Dunkelberger
    This works for Carbed, EFI, Ficht, HPDI, Opti-max and even 4-strokes... and should be administered after every 50-60 hours of use.
    First you need a separate small fuel tank. One of those 3-gallon red Tempos works well or an empty gallon milk jug in a pinch, but it might be a bit messier.
    I use Seafoam over the OEM (original equipment manufacturer) stuff like OMC Engine Tuner or Mercury Power Tune. Note: in the last few years they changed the formula and you have to let them sit up 12 hours. Who's got time for that? Seafoam does the job in 15 minutes and can be purchased from NAPA, Car Quest or other auto stores.
    You'll need 3/4 gallon of gasoline and one 16oz can of Seafoam for each engine. Don't forget to add 3oz of oil if you are pre-mixing in a carbed engine. Use a 3 ft piece of fuel hose off the small tank. Connect this tank to your engine by pulling off the main tank fuel hose from the intake side of your water separating fuel filter and plug the hose off the small tank onto that fitting. Or you can separate the fuel line on the tank side primer ball, so you can still use your primer. If your engine has a fuel plug then you will also need a fuel plug on the smaller tank's hose.
    Start the engine, let it warm up and start pulling the mix into the engine. You may have to increase the idle to keep it running once she gets loaded with the Seafoam. Run the engine 15 minutes at the dock or just cruising around under 2500 rpm's. Then shut it down and let it sit for another 15 minutes.
    Restart the engine; the smoke you see is the carbon burning off. Do the whole thing again and let her sit again for 15 more minutes. If she smokes after the second time do it again.
    I've never seen one still smoke after three doses. (I bought a Bronco two years ago that had 95,000 miles on it. When I used Seafoam on it I had the neighbors hanging out of their front doors looking for where the fire was after I started it the first time there so much smoke)
    The gallon mix should be just enough to do this 3 times. You don't need a wide-open throttle and you don't need to change the plugs. The plugs are cleaned at the same time as the combustion chambers. My suggestion is that every 50-60hrs is the optimal time to change plugs in most engines.
    I cleaned an antique Evinrude once that had a 1/4" of solid carbon on the exhaust chamber walls by running a 1/2 gal of the aforementioned mix through it. Seafoam, a great product, has been around since the 1930's and it's what they used when they were burning straight 4 stroke 40SAE oils in outboards.
    For you guys with the 4 stroke outboards? Those engines work 10 times as hard as any auto engine ever will and they too will carbon up. Too many are under the assumption that it's totally the 2 stroke oil that causes the carbon, Wrong... it's also the additives they put in the fuels today. The carbon inhibitors in 2-stroke oil are there for this reason also. Remember when gasoline used to smell like gasoline, today it smells more like bad cologne.
    For those guys that like to work the carbon treatment by spraying it down the carbs, Seafoam also comes in spray can called Deep Creep. It's the same stuff under pressure and notes on the can, "Oxygen Sensor Safe". After that, if your engine manufacturer recommends a daily additive treatment then do so. The tank and hose are a one-time purchase and the Seafoam is only costs $5-6.00 per can.
    Last edited by Bob_VT; May 19th, 2012, 12:27 PM.


  • #2
    Decarbing Your Engine- The Process-HOW AND WHY

    Decarbing is a 2 part process. The first part is preventative, done by using a fuel additive to prevent carbon build up. SeaFoam is one such fuel additive and can be found at most auto parts stores. It also works as a fuel system cleaner and should be used as a preventative maintenance procedure.If Your intent is to REMOVE the existing carbon buildup from the cylinders, heads, and rings, a spray decarb solvent product, such as SeaFoam Deep Creep, Power Tune, or Ring Free, is needed to do the decarb process. Free moving rings are what seals your cylinders and gives you compression. Compressed and stuck rings means loss of compression, broken rings, damaged pistons and heads, and eventually, engine failure.Run engine at fast idle, with engine running and warm, slowly spray liberal amount into each carb. Its gonna smoke up the place. Spray for a couple minutes, now spray a larger amount into the carb(s) until engine chokes out and stops.Remove spark plugs and spray the decarb product liberally into each cylinder, install the spark plugs, let it soak for an hour or more. Start the engine and run at medium throttle, or if at the lake, run it at full throttle. It won't hurt to spray some more through the carbs. Run it for atleast 10 minutes to flush the crud out of your engine. Now remove and clean, or replace the spark plugs. It works well to do the spraying, the night before you go to the lake. This way you can let it soak overnight, and run at full throttle at the lake.Don't do this in front of the garage door or the house, unless you want it covered with greasy black crud.************************************************** **********The following was posted by Dhadley, member #685. It explains the need for doing a decarb as part of your regular maintenance.""As for the carbon or coking, it all has to do with combustion temps and load in a 2 stroke outboard. We're not talking engine temps, but rather combustion temps. We're talking about an outboard, not a motor with very low and consistant exhaust restrictions like a motorcycle or a snowmobile or even a car.We're also talking about an engine that is always under a strain. Unlike a motorcycle or snowmobile or a car. An outboard must take off in high gear. Unlike other vehicles that have transmission that keep the motor "happy". Try that with your car. Outboards never coast. Would your car like that?Thru the years as the fuel changed we have seen this coking problem (carbon build up) get worse and then a bit better. It really seemed to help when the EPA removed MTBE from the fuel.Anyway, heres the results of some testing we did for OMC back in the mid 80's or so. It remains constant today.We used a V4 crossflow on a 16' boat. For the first part we loaded the motor up heavily -- dropped the X dimension and used a prop that would only allow a top rpm of 4800 with 2 people on board and 18 gal of gas. When it got light on fuel and only one person it would still only get to about 5200. Extreme? Yes, but it happens. Look on this board how many folks talk about their set up being close to this. At the time OMC was recommending that Engine Tune be used every 50 hours. We were still seeing coked up pistons and broken rings. On our test motor we coked up the pistons (starboard bank) in 12 hours of running. We broke rings at 19 1/2 hours. We rebuilt the motor and set it up on the same boat to turn 5800 with 2 people and 18 gal of fuel. We used no Engine Tune, no Carbon Guard or additives of any kind. Just OMC TCW II (I know, it was old school but thats what they wanted). After 500 hours there were no stuck rings or carbon issues of any kind. In both parts we ran the boat just as a pleasure boat. Cruising, idling, running flat out -- nothing special. The carbs were always clean, the water pressure was always correct, Champion plugs were always used as well as fresh 87 octane fuel.Now, if you look at combustion temps with that motor, the temps were much higher in the first test than the second test. High combustion temps promote coking. Coking leads to stuck rings. Eventually the rings break (more correctly the end is sheared off as the piston losses support).Hope that helps some.""************************************************** *********And this was added by DJ, member 5471.""Outboards are probably the most abused engines ever. An incorrectly propped engine is the norm, not the exception. That incorrect propping results in carbon build up. It has nothing to do with lead.Think about it. Some folks dole around at trolling speeds or non-planing speeds for hours. That leads to serious deposit build up. Add oil in the fuel and you get the problem described.Engines that run at high speeds for most of their lives may never have the issue.However, a decarb does NOT hurt anything, except maybe the plugs, and is a good preventive maintenance practice.BTW, the decarb. process has nothing to do with gunked up carburetors. That's a fuel storage issue best dealt with using fuel stabilizers.""
    Medford, WI

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