I got a Mariner 2.5 non-shift from a friend and need some help determining the year it was made. The serial number is OD977368. Also on the tag are the numbers "3D5" and "Mercury Marine Division of Brunswick Corp". Based on the styling and decals I'm assuming it to be mid to late 80's. Also, any idea who might have manufactured this model, such as Yamaha? Any input is appreciated.