Shurflo Extreme Series Smart Sensor Water Pressure System 4.0gpm Pump #275-4148153E75 The Smart Sensor 4gpm is a microprocessor control based variable speed pump that delivers over 4gpm and pressure up to 50 PSI. Corrosion resistant coated seamless motor shell and protected electronic package make the Smart Sensor; capable of handling the harsh marine environment. Thermally Protected. Ignition Protected. Self Priming Pump 3-Year Warranty.