What year is this motor?

I recently purchsed a used Mercury 18XD outboard motor. The previous owner thought is was manufactured during the 80's but did not know for sure.

The serial number is 6533463. The decals on the motor case are a golden brown if that helps. It has electric start.

I am also looking for an owners manual for this motor. Any help would be greatly appreciated.

It runs great, and does not appear to have been used very much over the years.

 

the color of the motor says out of the 80's but merc uses serial numbers for all part look up. but by the model it was only manufactored from 1980-1985