OK a couple of things. The little black lever is an electrical bypass. So it works the same way as if it were energized. The lever pushes that little white plunger down. That is what opens the valve.

That being said because it is a 24 volt solenoid it may not have enough juice to open the valve. I have not seen a 12 volt solenoid anywhere except the these boats. Do you have the old solenoids, or did you ever have them?

The little black lever should open the valve weather it is wired or not.