I have read many threads on other sites, not all relating to outboards, but am convinced enough to use SeaFoam over RingFree. I resotre 30-40 year old 2 stroke scooters and have seen unbelievable results with SeaFoam with regards to carbon. I also used it on my OX66 and it worked like a charm.
For those with 2 strokes, take a 2 gallon fuel cell and add the correct oil ratio (vary this if you are oil injected or not) along with SeaFoam and connect to your fuel bulb, bypassing the boat's fuel cell, and run the engine using this mixture and then turn it off and wait for 15 minutes. Reconnect the main fuel line and then notify the harbor patrol so they do not think that there is a fire and torch off your engine, you will piss so many people off with the amount of smoke that comes out, that is your carbon being burned off.
I have performed this with many 2 stroke engines and again, SeaFoam is amazing. My neighbors get a little upset when I am riding a scooter up and down the street after 'SeaFoaming', seriously, you will have people calling 911 thinking that there is a fire.
Anyway, RingFree is a great product, don't get me wrong, but I choose to use SeaFoam, available at any auto parts store.