The 1971 model Mercury 7.5, and the 9.8 hp, both have a solid metal cowling, rather than a band type so common to the day. The cowling release levers are cleverly concealed on the inside edge of the carrying handle, on the rear portion of the hood. There is a release lever on each side, pull these levers down to release the hood.
1971
A 65 hp Mercury outboard, serial number 3149254, is a 1971 year model.
An 20 hp Mercury outboard, serial number 3143107, is a 1971 year model.
1971
A 9.8 hp Mercury outboard, serial number 3177941, would be a 1971 year model.
By 1971, virtually all outboard manufacturers had gone to the 50-1 mix, and Mercury prided itself on being ahead of the game, so you are safe with the 50-1.
An 80 hp Mercury outboard, serial number 3055133, would be a 1971 year model.
You have a 1971 Us Made motor.
An 80 hp Mercury outboard, serial number 3057894, is a 1971 year model.
An 80 hp, Mercury outboard, serial number 3054480, would be a 1971 year model.
A 65 hp Mercury outboard, serial number 3076063, would be a 1971 year model.
A 9.8 hp Mercury outboard, serial number 3089762, would be an 1971 year model.