If it has had " normal " use with a 24:1 mixture then I doubt that the rings are worn out.-----------Will spark jump an actual gap of 1/4" with a snap you can hear ?------Poor spark is a major reason for the " hard to start condition " on these motors.----Yes they will leave a trail on the water and that was normal for a 1950's design.-Simple tools and common sense is all that is needed to repair and maintain one of these.--------If you do a real search on google you can find a manual that covers that motor.----------Look for " johnson 1922 to 1964 " and it should come up for you. Hundreds of pages of good outboard information , including your motor.