Bilge Pump Discharge - New Thru Hull ???
Expect you''ll get some contrary advice, but:
If your intent is to add an automatic bilge pump, for use when boat untended - your idea has merit.
There''s, obviously a trade-off here. You''ll still only have one pump available (at a time), and would want to ensure that the diverter ("Y") valve is quickly accessable, and preferably c/w mounting feet/flanges (fasten to bulkhead or whatever). Ensure that you don''t "foul" the discharge (vented) loop, and adapt from the .75" pump discharge to the 1.5" overboard discharge as early as possible. NO CHECK VALVES!