The serial number tag is found on the SWIVEL BRACKET (port or starboard); or, check the INSTRUCTION PLATE, Positioned in between the thumb screws above the steering tube. By coming into your email address you conform to get marketing messages from Yamaha Outboards. Chances are you'll unsubscribe at any time. https://ebayoutboardmotorsyamaha53951.blogripley.com/37714184/top-latest-five-yamaha-150-balancer-issues-urban-news