I am having a hard time finding a way to route a line from a powered bilge pump to a location where I can put a thru hull. ( there probably is a way... but I just have not figured it out yet).

So I got to wondering can I run the output of a powered bilge pump through a manual bilge pump... will the valves simply open in the line of flow, and allow the water to just go through?

Of course the converse of that is, with a manual pump, can I draw though a powered bilge pump? Again the flow is in the same direction.

Imagine that I am putting a Rule pump (or similar) down in the bilge, with a float switch, but I have an existing Guzzler 500 mounted at the end of about 5 feet of hose up in my lazerette. Can I put these pumps in "tandem?" Is there anyway that will work?

Of course the better idea is redundant and separate systems. But just for a moment, let's entertain the concept I put forth.