looks like about 1975 http://www.crowleymarine.com/brp_parts/731.cfm
Its a 1975 model
1975 model so it's 35-yo in 2010
your Johnson is a 1985 year model
Johnson outboard model number J175EXARG, would be a 1994 year model.
A 50hp Johnson outboard, model TELCUD, is a 1987 year model.
A Johnson 70 hp outboard, model number J70TLETS, would be a 1993 year model.
A Johnson, model number J10BACDB, is a 1986 year model. 1999
Johnson model number J10RCCD, is a 1988 year model, 9.9 hp outboard.
A 4 hp Johnson outboard, model number J4REIA, is a 1991 year model.
A 175 hp Johnson outboard, model number J175TXCSA, would be a 1980 year model.
A 90 hp Johnson outboard, model number J90PLEEB, would be a 1999 year model.
Model number 15R745, would be a 1974 year model Johnson outboard.