Mercury - Tachometer 6K Engine Speed Monitoring White Face Chrome Bezel 79-8M6020013. OverviewThis 6,000-RPM tachometer gives you a steady, easy read on how the engine's running without the needle bouncing every time the boat shifts. The sweep feels natural, so you can grab your RPMs with a quick glance and stay focused on the water. Out on a long run, it settles in fast and lines up with what the engine sounds like. It's a simple, clean-looking gauge that fits right into the rhythm of the day..