Youll have to go to a Merc parts dealer. You dont have to have all SmartCraft gauges, but the speedo wont work alone without the tach. The tach alone works but it is the main unit and all the rest feed off of it. What youll need is a blue cable with the yellow terminators on each end, a 4-port hub, and the appropriate cable for each of the SmartTach and SmartSpeed gauges. On the engine side you way also need another harness if its not already installed. Its really pretty easy to do once you figure out the exact cabling that you need. Deke[font="]Deke[/font]