Re: 20 hp johnson sea horse help
What is your model number?
I think 1965 was the first year that used a 50:1 ratio, many still used a 24:1 for several years after that date. I am sure others will chime in with more comments.
Do you have a dealer close, or a napa store, they can get them for you without having to pay freight. You might as well get enough for several oil changes so you have them on hand.
I think the OEM number is 311598, or the sierra number is 184248, double check the numbers before ordering.