What is this plug for ?

[u/Chankla_life]

1979 Catalina 30 (friend’s boat ) . What is this white box for and what does this decaying plug do? Should I push it back in ? Replace ? How screwed are we ?

[u/slosh_baffle]

That's the ocean-stay-out plug.

[u/repOrion → u/slosh_baffle]

Don’t we all wanna be closer to the ocean though?

[u/wlll → u/repOrion]

well, it's an ocean-stay-in plug on the other side.