First let me say I don't buy into the hype of manufacture specific oil as being the "only option". I do understand that most OEM oils exceed the TC-W3 certifications required to meet most outboard manufactures warranties and recommendations. With that said from the research I have done the TC-W3 standards are pretty stringent and any oil that meets that standard should be more then adequate to protect your engine.
I am not a fan of yamalube with the high amount of moly and carbons it produces and the requirement to run ring free in every tank. I understand moly is for wear protection but think it could be overkill and a little bit of a marketing strategy..
I ran Super Tech from Wal-Mart in my old Mariner and it was a clean burning oil and never gave me any problems. In my newer HPDI I try to run penzoil when I can get it but have ran the super tech from time to time also.
What are your opinions on oil and how often do you run additives such as sea foam, stabil etc? I run Stabil at every other fill up and so far have had no issues with carbon.