What year is my 40horse?

Hi I just got my first boat and Im trying to find out what year my motor is. It's a 40h but I cant find a model number. The only clue I can give you is that its a twin cyclinder (I see most other 40's have 3), and its blue. Sorry I know thats not a lot of info. Any ideas?

Also, can I just use any 80/90 gear oil in my transmission, or is there a specail marine oil I need to use?

Thanks

[boats.net]

Without model number there's not much chance of determining year, take it to a Yamaha dealer to see if they can tell. Use outboard gearcase lube in lower unit.