A Johnson model FD-19D is a 1965 18 hp outboard.
1965 18 hp
1975 20hp johnson
1968 20hp
1966
To determine the year of your Johnson 20hp outboard with model number FD-20C and serial number J2604167, you can refer to the Johnson outboard motor's serial number guide, which typically indicates that the first digit of the serial number represents the year of manufacture. In this case, "J" typically corresponds to 1988. Therefore, your outboard motor is likely from the year 1988.
I don't have the Mariner year model chart, but close as I can tell this engine would be a 1984 - 1985 year model.
your Johnson is a 1985 year model
A 20 hp Mercury outboard, serial number OB152174, would be a 1987 year model.
An 20 hp Mercury outboard, serial number 3143107, is a 1971 year model.
A 50hp Johnson outboard, model TELCUD, is a 1987 year model.
Johnson model number J10RCCD, is a 1988 year model, 9.9 hp outboard.
Johnson outboard model number J175EXARG, would be a 1994 year model.