I am trying to replace my livewell pump with a new one. It is an old Atwood 500, not the tsunami kind.

I think it may have that 5200 sealant. How do I get this thing out? I've really wrenched on the not outside and can't get it to budge.

Are you just replacing the cartridge pump or the whole assembly?  If you think It's sealer pour a bit of acetone into where you think it's holding.  Give it ten minutes then yank her out...  Good luck

I'm trying to replace the whole thing. I can't find that model or cartridge pump anymore.