The number on the freeze plug is your engine serial number, 0B374043, the preceding digit is left off. You'll have to wait for one of the gurus to provide the year, that info is not provided with serial number lookup. This engine will be covered in one of the forums below:
0B374043 is a 200hp Mercury 2.4L (carb model), and was born on 05/07/1988. Keep in mind that Mercury doesn't use "years" so you'll always want to refer to the Serial Number to identify the engine.