Mercury - Tachometer 7K Engine Speed Monitoring White Face Chrome Bezel 79-8M6020014. OverviewThis 7,000-RPM tachometer gives you a steady feel for how the engine's running, even when the boat moves through chop. The sweep is smooth and predictable, so you can grab your RPMs with a quick glance. Out on the water, the reading usually matches what you hear from the engine, which makes cruising or trimming out feel more natural. It's a simple, clean-looking gauge that fits right into everyday use..