38' special When I turn on main panel in cuddy I here a pump running .Does any body know were this pump is located at

I'd guess it's the bilge pump in the engine compartment.
I've seen boats that had them powered directly from the battery on a fuse with float actuation that would turn on even if the battery switches were turned off to power up the main panel.

See ya,
Kelly

Im guessing either the fresh water pump,,,,,,or the vacuflush pump

That's what I thought the fresh water pump
Were is it located ?