The serial number tag is situated to the SWIVEL BRACKET (port or starboard); or, check the INSTRUCTION PLATE, located involving the thumb screws above the steering tube. The good thing is, PartsVu has a wealth of resources that may help you find the Mercury outboard parts you need to maintain https://yamaha-outboard-motors-nz11974.bloggip.com/36969293/detailed-notes-on-bf75-honda-outboard