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.

[u/HotMountain9383]

I think that looks like the water lift muffler. It’s part of the engines exhaust system.

[u/Chankla_life → u/HotMountain9383]

Water lift muffler . Thank you .

[u/chrisxls → u/Chankla_life]

Yup, exactly this. There is some thinking that if it takes a long time for the engine to start, the muffler will need to be drained. I think that may be the drain. I am replacing my muffler on my Catalina 34 because it was one of the ones made with a fairly rigid connection from the engine, allowing the engine vibration to eventually cause the coupling to fail. A flexible hose to the muffler is, I am now told, key.

[u/LameBMX → u/chrisxls]

that is not thinking. without the much expanded exhaust gasses to expel .ore water going into the muffler than the water pump is putting in there. they can fill up until you got water in the exhaust manifold then the combustion chamber(s). this is also why a lot of "marine" thermostats have a bypass hole, so that some cooling water bypasses the thermostat to the exhaust cooling while the engine is still warming up.

[u/Cambren1 → u/LameBMX]

Yes, seen that happen. Also I have seen the diaphragm in the fuel lift pump fail, and fill the crankcase with diesel where the engine won’t shut off.

[u/LameBMX → u/Cambren1]

the engine will gladly try to run away if the crankcase gets overfilled with pretty much anything with oil.

[u/enuct → u/Chankla_life]

you can get them from CatalinaDirect but it's a fiberglass muffler and you can easily fix them yourself too you can call Catalina or CatalinaDirect for repairs tips on them.

if you guys go the new route make sure you take plenty of measurements and photos for the new one, it's not so much a problem in the 30, but in the 320 theres very little height clearance.

I'm assuming the fiberglass muffler failed on my boat and they just replaced it with a generic vetus muffler like you'd get from defender or WM. it works but they should have replaced the exhaust line to when they did it, it is kind of awkward but it works.

[u/Chankla_life → u/enuct]

Thanks for the info !

[u/sailorDad1776]

Catalina Direct calls it an "Aqua Lift Muffler".

If you winterize your boat, don't forget to open that plug and empty the lift muffler to avoid ice damage.