What is this?

[MMHagler]

...and what does it do? I cleaned up my trim pump and when I was testing it there was this plastic hose with a brass fitting sitting there and I don't remember taking it off,but that was a month ago and I know now you should take pictures. It comes from picture 1 across to the pump area and you can see it in picture 2 under the blue speaker wire...pump is working up and down with 2 other hydraulic hoses attached,any ideas? Thx

 

[Alumarine]

It looks like you have an older mercruiser.
Is your trim gauge working?
That horizontal tube is the trim sender and it looks like there is air in the line.
Maybe someone disconnected it?

 

[MMHagler]

No my trim gauge reads half and spikes when I raise the motor so I pulled the purple and blue plug... I have no idea where that plastic hose would hook up too anyways,don't see anywhere it would go.