Mercury – Service Monitor | Engine Hour & Warning Indicator | 79-8M0050399Mercury Service Monitor Engine Hour & Warning Indicator 79 8M0050399 OverviewThis Service Monitor is a simple way to keep track of engine hours and maintenance intervals on most Mercury outboards and gasoline MCM MIE engines. It replaces older versions with a universal style unit that installs cleanly and works the same across a wide range of setups. On the water, it gives you a quick way to monitor run time so you can stay on top of routine service.