OMC & Merc each have their own brand, which is probably no different than SeaFoam. It's a top end cleaner which removes carbon from the combustion chamber & rings. Supposed to be used once a year maybe, I don't remember the recommended frequency of use but I use it once a year on my early 1980's 10hp merc and 1970's 18hp evinrude. Not really an additive since it's a one time use. But it really does work and helps clean carbon buildup, which is kind of inevitable in 2-cycle engines. Yamaha also has an additive, more along the lines off what you are asking, which prevents rings from sticking. Although that should be the job of the 2-stroke oil I think, but a buddy with a 250hp yamaha on a 24' grady uses it religiously for the past 8 years or so and hasn't had a problem.
