CDI M.E.D.S. (Upgrade 531-0118M/MP to Add Yamaha)Product Description: Marine Engine Diagnostic System; M.E.D.S. Yamaha Add-On; Adds Compatibility with Select Yamaha Engines, Yamaha PWCs and Mercury Engines built by Yamaha; This part is for use with your current M.E.D.S. system to add Yamaha capability; It includes a software upgrade to the latest version.; Replaces: 531-0119Y;