My father’s outboard motor came used with his boat. He debated replacing the motor entirely, but really that was going to be fairly expensive. The motor that he had was running well enough that buying a new one wasn’t actually necessary. My father decided that he would at least use the used motor until he had the money to replace it.
Since he wanted to start with a motor that was at least closer to new, he first ran it with Yamalube ringfree plus. His hope was to get rid of any of the build up in the engine that might have been left there overtime. It seemed to work, because the motor ran well and he didn’t have any problems with it for the first several years that he owned it.