Auto bilge?

I don't understand how the bilge pump works on my boat. There is off, manual and auto. When I flip it to manual, it seems to just run constantly, just at a slower pace. I had some water in my bilge the other day and flipped it to manual and it really started pumping out the water. When I flipped it to auto, the water kept coming out, just slower. If I leave it on auto, it runs continuously even if there is no water in the bilge?

when set to auto it should only run when there is water in the bilge. there is typically a float inside the pump housing that switches the pump on when the water level in the bilge is high enough. if it is running constantly when set to auto - with no water in the bilge, the float may be stuck, or the internal switch may be bad.

^ That is why mechanical floats suck! Solid state electronics are much more reliable.

Check for debris in the float area. The float could be part of the pump assembly.

The pump should pump the same speed whether it is on auto or manual.