Cast iron sewer pipe fittings

I found a crack in the bottom of a 2" cast iron service Y, (at single end) and I need to patch or cut out and replace with PVC and rubber connectors under the house. How are these joined? Are they threaded or is there a mastic poured into the union for a watertight fit? The location sucks, right next to a pier, it has about 1/2 inch below it until concrete and there are 3 of these suckers daisy chained together. Mine is the last one to the run the street. Im thinking a rubber patch held on with a metal sleeve and pipe clamped. Thats where my rodent problem started, standing water under the house, but only a dirty rat would drink that ****. (No brown water, only grey sink/dishwasher and washing machine drainage.)

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