Come on OP you didn't really need to ask did you? That's not just
corrosion that's rotted out. Looks like someone has done some
work on it too. The
compression post fixing looks new and it's just been bolted on to the old beam. Yuk. It shouldn't be an especially big job though. Presumably
mast will need to come down, but perhaps possible to just jack up for access. You wouldn't want to be crossing oceans with it like that. But as always difficult to tell from a
single photo taken on an unknown
boat.
It's always interesting what you see on CF. I have a badly rusted beam too. It's been a slight concern to me since I bought the
boat, and rust never sleeps as we know. But at least my
surveyor picked it up and we had a discussion as to what's involved in
repair. That's a
classic place for rust.