I replaced the speedometer with the MercMonitor. Didn't need it anyway. Mercury motors use the "CAN" communication protocol instead of the NMEA 2000 used on other outboards so you have to have a gateway to change the protocol. You can purchase one without the MercMonitor and hook directly to your HDS but I don't know if it displays all the same functions as the MercMonitor. Don Weed can advise you on that. I don't think an HDS12 would fit well on the console but the 9 inch is perfect. I see that Randy with Precision Sonar weighed in with some photo's, he is a good guy to work with. On the bow unit, I use the Precision Sonar unit shown in Randy's pictures except I have the shorter one. However I wish I had the taller one and for sure on a 2015 you need that one since your pedal tray comes all the way to the front and you will need the extra height to clear the tool holder. The picture shows my old HDS mounted on the bow but it shows the eLocks I use for security on the current HDS9T. You will also notice that I drilled a hole through the mounting bracket and installed a lock. I also attached the sonar bracket to the deck with security screws and locknuts under the deck so you have to remove the trolling motor tray to remove the sonar bracket. I also have a lock-R-Bar covering all the deck hatches. My boat resides on a lift in my boat stall and I don't want to have to remove all the gear every night.Attachment 188176