HOW DO I FIND THE BOAT MOTOR'S YEAR WITH THE SERIAL NUMBER?

i HAVE TWO BOAT MOTORS IN MY GARAGE THAT BELONGED TO MY GRANDFATHER. i WANT TO SELL THEM BUT I DON'T KNOW HOW MUCH TO ASK FOR THEM. tHEY ARE BOTH MERCURYS. oNE IS WHITE AND IS A MODEL MARK 55A-E AND THE OTHER IS A 9.8HP THUNDERBOLT INGITION MECURY MARINA