Cast iron sewer pipe fittings

Yeah, setting rat traps I noticed a big mud piddle, then I crawled back and fouND standing water. O crap...I told wife to run sink and I heard the water leaking out the bottoM so I felt under there and almost pushed my finger into the pipe, makING the hole 2x bigger than it stared but I did get it back to some solid metal. That's when I stuffed some rubber in there and duct taped it. I'll wait a few more days so the lake subsides down there, it's already soaked down to just mud now. Ill have to get eyes on it again to determine if I can cut that y out and replace it with PVC. House was built 1951. I have some mighty putty but it's hard as a rock now. I was going to epoxy the rubber patch and clamp it. All ready found a 2" rubber union that will work perfectly if I can get it under that pipe. It's almost sitting on a concrete pier or it made a stalagmite there.