Oil Sensor Short

I have twin 1995 200's. In the last month have had 3 oil sensor gauges short out. The engine is running fine. I have replaced the pump and in-line filter. The emergency switch works fine and the sensor in the resevior on the engine works fine. Recently I just by passed the tank sensor and everything works fine. Any idea why the sensor was shorting out????

[boats.net]

The sensors in oil tank in boat don't usually give much trouble but the wire harness going to tank does, corrosion problems cause harness to go bad.