H20 Pressure Sensor Issues

[djbaumhover]

I have a 2004 Sundancer with 6.2's, and Bravo III outdrives. I've one H20 sensor reading approximately 1.1 at idle while the other reads 13.5. If I swap sensors from one engine to the other, the sensor will read in the 1.1 range. My understanding is at idle, the 1.0 number is good. I've purchased a couple of different sensors on the internet (from China) in the $20 - $30 price range and they don't appear to work. The one I just received won't register at all, 0.0, while another purchased last year reads 40.0 at idle. Is any type of reset required when installing these sensors? Is it necessary to apply a thread sealer when installing?
Both SmartCraft and analog temp and oil pressure gauges read fine. Is it necessary to purchase the expensive Mercruiser units to get a good H20 reading?

 

[scoflaw]

Apparently so ..I could care less about water pressure, my boat doesn't have 1. One more thing to break.

Downside, if your ecm doesn't like what it's seein for a value, it will put your boat into guardian mode and no one likes that.