Rotted Cabin Floor

[Diggity]

Removed the carpet in the cabin to replace with luxury vinyl and found the floor board is rotted. Started pulling out the rotted part and found the back support beam shown in the second photo is rotted as well.

Any advise on how to replace the beam? Only looks to be a couple feet wide but it connects to both stringers. Not really sure how to reinstall a new board.

[shrew]

Any support that is acting like a 'joist' is a stringer. They don't need to run bow to stern. Yo have a rotted stringer.

1) Remove ALL rot

2) Identify the source of the leak

3) Fix leak

4) Fix stringers, sole and any rotted bulkheads.

That stringer would normally be encapsulated in fiberglass and resin. It doesn't appear to be. It looks like wet PT.