Last year they had offered for the first time ever a winter schedule at all with 1 boat. These year they even extented the winter schedule.

k-d.com/englisch/schiffstouren/winterprogram…

Too cold? No one forces you to travel on the open decks. There are of course indoor decks with panoramic windows.

As a rule of thumb: the colder it is the better is the weather.

With the short daylight period in Winter and the fewer tourists (off-season) they cannot offer a schedule like in summer.

You can travel with the boat from Bingen to St. Goarshausen and from there by train to Braubach. Boppard is on the "wrong" side of the river if the destination is Braubach.

http://reiseauskunft.bahn.de/bin/query.exe/en

From: St. Goarshausen Bahnhof

To: Braubach Bahnhof

KD boat Bingen to St. Goarshausen is EUR 14,60.

At each KD landing stage you will receive a 20% discount off the KD schedule tariffs when you present a valid German Rail ticket.

I imagine you mean 2005, right?

Good advice from abalada. From the docks in St. Goarshausen, walk north along the main street several blocks; the station will be on your right. You may need to walk up to the castle - a steep 20-30 minute walk - if the MarKsburg Express (shuttle) isn't running at that time of year.