SeaFoam is one of the preferred products for de-carbonizing the engine components. Due to its success, it is the choice of many people here, including myself, for that specific function.
Berryman B-12 like Gumout, is a product that is recommended for cleaning carburetors and fuel injectors, which has little to do with the de-carb process.
50:1 oil mixture plus the seafoam. I know there are threads with decarb.
instructions here on iboats. Tas has posted it more than a few times so
I'll be able to find it when the time comes. Thanks Tas