traverse via Wasseralm and Stuhljochgrat.
take the first boat at 8:00 to start at 9:00.
The schedule to reach the last boat at 17:40 from Salet is tight. You must be fast and must not have long breaks.
from Kärlingerhaus either go down as planned, or if you have enough time, via Saugasse (3km more, 100m gain less, 1h more) to St. Bartholomä. Sägeretsteig is very steep and partially prone to rockfall.
If you are too slow, you could return via Wimbachgriess (17km/400m gain/4h longer) without boat https://www.hiking-buddies.com/routes/routes_list/2400/
more details and pictures https://www.stefanmitterer.de/funtenseetauern-2014.html