Anyone know what these two vacuum switches do and why the black one on the left would not be hooked up?

It is a 2004 Mercury 200 EFI

Thanks

Did you try asking this question over on Scream-n-fly.com? They will probobly know.
I have a 2005 225 EFI Merc. 3.0 Liter, and I'll try to take a look tonight, if it's not raining, and see what is hooked up on my motor.
Dean

I will try S&F but I don't go there often. Thanks for the help

The one that is hooked up looks like its for water pressure guage or pressure alarm. the one thats not hooked up should be the other one. If your w/p guage(assuming that you have one) is electical this would be the sending unit. If the guage is mechanical then this is sender for low pressure alarm. Engines are wired so they can be used either way for different installations.
This is just my educated guess. Hope it helps

Thanks

The pressure sender on the left looks to be for your speedo and the one on the right is for water pressure. Water pressure usually has a grey tube and speedo usually has a black tube.

If you need more info call me at the shop.

John

Thanks Guys. I was wondering why the one would not be hooked up from the factory. They look more important than they are.

pwrbt33 has it right. Those are just pressure sensors for the smartcraft gauges.