Re: 1982 Johnson 25 hp
I don't believe there is a "seal" between the mid section and the lower unit. At least there isn't on my '85 Johnson. <br /><br />The lower unit is sealed, but it just fits up against the midsection. The black crud leaking out, is exhaust residue buildup (carbon and oil), that gets hung up in the midsection of the motor. Not a problem.<br /><br />But if you want to clean it up, and remove a whole lot of potentially damaging carbon from your rings and heads, then do a thorough decarb process. What is that? I'm glad you asked.<br /><br />Decarbing is a 2 part process. The first part is preventative, done by using a fuel additive to prevent carbon build up. SeaFoam or Ring Free are such fuel additives 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.<br /><br />If your intent is REMOVE the existing carbon buildup from the cylinders, heads, and rings, then a spray decarb solvent product is needed. Buy at least 2 cans of decarb. Some people use one can per cylinder.<br /><br />Run engine at fast idle, with engine running, slowly spray liberal amount into each carb,<br />spray some more, spray a larger amount into carbs until engine chokes out and stops,<br />remove spark plugs and spray decarb liberally into each cylinder, install the spark plugs, let it soak for 1 to 10 hours. <br />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.
