There may not be a dedicated NMEA2000 output on your Yamaha, but there will be a data port where, with nothing more than two wires, you can deliver engine data to a drop on your NMEA2000 backbone. Then, after identifying the physical connection points and routing it to your backbone, you configure your HDS to receive the data. Configuration will include which engine - port, starboard or center (your application will be center) and other configuration points, then you'll have data.
A fuel level sensor (also to your backbone) and a GPS antenna (again also to your backbone), you can have MPG and other fuel use data.
Now, which data you get from your engine depends on the engine. As an example, 2008 Suzuki does not show oil or water pressure data, but my Yamaha did. So, your Yamaha may not show certain data points.
My 215cc had a 2007 Yamaha, and I had two micro spade connectors on two of the output port connectors and those two wires went to the backbone (sorry, I can't remember which ones). I had more data than I could display on my Raymarine. So, it can be done. Start with the backbone. Check the service manual for your engine and identify which to points to connect to. Follow the advice of others about building a backbone.
I hope I gave you hope and not confusion.
