Mercury - Water Pressure Gauge 0-30 PSI Cooling System Monitoring Black Face Chrome Bezel 79-8M6020007. OverviewThis 0-30 PSI water-pressure gauge gives you a steady, no-nonsense read on how well the engine is pulling water. The needle settles in with a smooth, slow sweep, so you can spot real pressure changes without fighting jitter from wakes or chop. Out on the water, it turns into a quick habit-glance, register the number, and stay focused on the run. It's a simple, practical gauge that help