The serial number tag is located around the SWIVEL BRACKET (port or starboard); or, check the INSTRUCTION PLATE, Found amongst the thumb screws above the steering tube. Luckily, PartsVu has a wealth of resources to help you find the Mercury outboard parts you need to keep the engine running efficiently, https://jaredpmcqx.ampedpages.com/fascination-about-yamaha-115hp-2-stroke-outboard-63789312