Those Sea Kings were made under Gale motors, which were an OMC company up until 1963. In 1964, they were a Chrysler company. I am told that the 15 horse Sea King up to 1963 is a real close match to a 1956 15 horse Johnson/Evinrude but has a fiberglass hood, and other minor differences. They were set to run at 24:1 oil mix, but with todays modern TCW3 oils, some people decide to run them 50:1. I personally would keep with 24:1, and if I really got to know the motor, and find out what it likes, I might jump up to 32:1. But, chances are, if I owned one, I would fill it out of my 24:1 can, as opposed to my 32:1 can. (Wait, I don't have a can designated for 32:1 :roll: )