Mercury - Water Pressure Gauge 0-30 PSI Cooling System Monitoring White Face Brushed Bezel 79-8M6020067. OverviewThis 0-30 PSI water-pressure gauge gives you a steady read on how well the engine is pulling water through the cooling system. The needle moves with a smooth, relaxed swing, so you can catch real changes without chasing jitter. Out on the water, it reacts the way you expect-whether you're trimming up, running skinny, or pushing through a bit of chop. It's a simple gauge that quickly w