[ReelNauti]

It depends on how your pumping out, overboard or through the deck plate.

On my boat (1994) there are 3 things you need to do to pump overboard. Just a side note, this is only legal over 3 miles offshore. Many localities now make it mandatory that the overboard discharge is physically locked out to prevent accidental discharges. Many boats now do not even have the ability for overboard discharge.

First was switch the y-valve in the engine room.
Second was to open the sea cock under the large deck hatch which also requires removing the tub.
Third was to turn the macerator pump on.

For the deck plate, the y-valve must be turned to the deck plate. This is how I keep mine setup since I have not pumped out offshore in years. My macerator died and it just wasn't worth replacing.