The serial number tag is found on the SWIVEL BRACKET (port or starboard); or, check the INSTRUCTION PLATE, Found among the thumb screws above the steering tube. Thankfully, PartsVu contains a wealth of resources to assist you to find the Mercury outboard parts you need to keep the engine running https://yamaha-outboard-motors30524.blogzet.com/top-boat-marine-temperature-switch-secrets-51656764