Need help with model year charts

[boats.net]

No none of those numbers mean anything, look on engine block for round aluminum plug(looks like a freeze plug) with model/serial number. stamped in it

[Shell_shooter]

Bought a boat with 20 hp evenrude motor ,there are no numbers on the sticker I'd plate but got these 2 numbers that are in the book I got with it EO668538. and. ACBK3557M87H
any help would be appreciated