Mercury - Water Pressure Gauge 0-30 PSI Cooling System Monitoring White Face Black Bezel 79-8M6020055. OverviewThis 0-30 PSI water-pressure gauge gives you a steady, easy read on how well the engine is pulling water through the cooling system. The needle moves with a smooth, relaxed sweep, so real changes stand out instead of getting lost in jitter. Out on the water, it reacts the way you expect when you trim up, run shallow, or ease into heavier chop. It's a simple, dependable gauge that become