The Mercury OEM 14570 water sensing probe for the fuel filter is used in the engine-mounted fuel filter system on selected Mercury and Mariner EFI two-stroke outboards. Its purpose is to detect water that has collected in the fuel filter and provide a signal to the engine warning system.
Water contamination can cause poor idle quality, hesitation, hard starting, injector problems, and corrosion inside the fuel system. On engines equipped with the 14570 probe, water that settles in the bottom of the filter can be detected before a larger amount reaches the fuel system.
The 14570 is a fuel-system water sensing probe, not a coolant temperature sensor, water-pressure sensor, or cylinder-head temperature sensor.
Mercury 14570 Fitment
The 14570 was used on selected Mercury EFI V6 outboards, including many V-135, V-150, V-175, and V-200 engines from the late 1980s and 1990s. It is also found on compatible 150 XRi, 175 XRi, 200 XRi, 220 Laser, and Magnum EFI applications.
Mercury also used this probe on selected high-performance EFI engines, including 150 Pro Max / Super Magnum, 200 Pro Max / Super Magnum and 225 Pro Max / Super Magnum models.
The probe is also found on selected early 225 HP and 250 HP 3.0L EFI outboards. Because Mercury used more than one fuel-filter and sensing arrangement over the years, fitment should always be confirmed by the engine serial number and the actual fuel-filter assembly installed on the engine.
How the Water Probe Works
Water is heavier than gasoline and settles toward the bottom of the fuel filter. When enough water reaches the sensing area, the probe changes the electrical condition of the warning circuit and allows the engine warning system to indicate a water-in-fuel condition.
If a warning occurs, the filter should be inspected before assuming the probe has failed. Check for actual water contamination, damaged wiring, corroded terminals, or a poor electrical connection at the probe.
Buckshot Racing #77 Tech Tip
These older Mercury EFI engines have often had fuel-system parts, powerheads, or filter assemblies replaced over the years. Because of that, the engine model alone may not be enough to confirm the correct sensor.
For best results, identify the engine serial number and the actual fuel-filter assembly currently installed before ordering a replacement probe.
The Mercury 14570 Water Sensing Probe is a replacement water-detection component for compatible classic Mercury and Mariner EFI fuel systems, including many 135, 150, 175, 200, 220, Pro Max, Super Magnum, and early 225/250 3.0L EFI outboards.
Make sure your sensor is black, not blue!