Water Pressure Gauge Tubing

[TownsendsFJR1300]

water can absorb air over time, so I am sure either there was a very small air leak or air was absorbed over time to allow that much water to get up the tubing

I have to disagree...

With a "V" cut in a 3/8" ID hose, about 60 PSI at the hose. I turn the ignition ON(engine off), put that V cut hose with 60 PSI at the pitot tube opening (in the LU), the speedometer reads about 17 MPH.

My boat, WOT will do about 46 MPH. There's considerably MORE water pressure while running to / for the speedometer to read 46MPH.

IE, there's quite a bit of water that gets pushed up that small tube (and if the hose isn't exactly angled downward-which most boats won't be-where the wiring, etc are routed) and remains, (unless pressurized out)..


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[99yam40]

In a well sealed system( no leaks) the water will pressurize the air in the tube, and that pressurized air will push the water back out when the water pressure goes down or away, as long as the air pressure does not leak out somewhere else or some of that pressurized air is absorbed into the water that is pushing on the air.

It is truly amazing to me that O2 will make its way thru sealed containers/tubes due to the small size of the molecules.
Back when working around gas analyzers techs, they tried to teach me some stuff that was strange to me

[Jason2tpa]

It's logical to assume that as a semi permeable membrane expands so too do the atoms that are holding the membrane together (contruct). Expand the membrane enough and atoms smaller than the membranes contruct atoms would be able to pass through.