What is This? It has Mercury on it.

[Berdink]

The line going to it appears to be a small hose line.

 

[Mc Tool]

Its a speedo pick up ....water is forced up that tube and goes to a pressure gauge on the dash that has mph on the dial .....pretty old tech and notoriously innaccurate but better than nothing ...last century

 

[Berdink]

Okay, yep, the boat has a speedometer.
Thanks

 

[boscoe99]

Its a speedo pick up ....water is forced up that tube and goes to a pressure gauge on the dash that has mph on the dial .....pretty old tech and notoriously innaccurate but better than nothing ...last century

All modern aircraft still use a pitot tube for speed.

Only way to know their airspeed. Speed through the air.

Pretty much the same except for a boat which has an alternative. That being a paddle wheel for speed.

 

[99yam40]

You can always use GPS speed if you are not too particular on the difference in water speed and GPS, land speed.
currents do affect water speeds, going with or against the current

 

[Mc Tool]

argh craparama here we go again ! I remember all the bickering over this topic last time , that planes use pitot tubes for airspeed .....and gps verses pitot , speed over ground verses water speed , but we were talking (old ) boats here , specifically "what is this? "

 

[boscoe99]

There should be no bickering.

If one wants speed through the water use a pitot tube or paddle wheel speedometer.

If one wants speed across the the land* use a GPS speedometer.

Those on land care not a whit about speed through the water. Why do people boating in water care about speed over land. Land that might be thousands of feet under them.

* Sorta but not really.