How can I Decipher mercury outboard serial number 7097210?

The serial number, along with the horse power for Mercury outboards, will tell you the year model only. The serial number, and hp rating of a particular engine, is compared to a model year chart to determine the year of manufacture. Models produced in the early 80's and later, also have a model and year designation printed on the serial number label. Example.... 90ELPTO, 90hp, electric start, power trim, oil injected.