Cruising down the Rhine from Cologne to Bacharach

Sally: You won't have the time to make the boat. You should consider either taking an early train or staying in Cologne for the night. It's quite an underrated city, and the Duomo is not to be missed.
We have stayed at Bacharach a couple of times. It's just a little, quiet town with a small train line running along side the Rhine River. Bacharach is a good place to recharge before catching the train down to Frankfort Airport and points south.

I think you would be best to take the train to Koblenz and catch a boat there. 15 minutes will not make it. The stretch from Koln to Koblenz is not as spectacular anyway. If you have time, you could spend at least an hour or two in Koln, the Cathedral is just outside the train station, and the area beyond is a nice pedestrian mall, plus have some refreshing Kolsch beer. At Koblenz, the boats are more frequent heading to Bacharach, if you have more time that day, just stay on the boat past Bacharach until later in the afternoon, then take the train back to bacharach.

In Köln, the KD dock is a few hundred yards from the Hbf. You could probably make it walking if you knew exactly where you were going. There are probably taxis that could take you there in time, but it is still iffy. The KD dock is a long way from the station in Koblenz. There are buses. Just for reference, the Rhein flows from the SE (Bacharach) to the NW (Koeln), so when you cruise "down" the Rhein from Koeln to Bacharach you are actually going UP the River, against the current. Why is this important? The current on the Rhein is very strong. It can take twice as long or more to go "down" the river.

You are cutting it way too thin. Take the train to Koblenz and pick up the boat there. It is a long way to the dock in Koblenz but you should have time or take a cab if need be. How much luggage yo have may make that decision for you. You won't be missing anything scenerywise, the Rhine from Cologne Koblenz is dull.

"the Rhine from Cologne Koblenz is dull." Allow me to respectfully disagree. Yes, you won't find the density of castles comparable to the more well-known section, and there is a rather ugly short industrial strip just north of Koblenz. But running south from Bonn, the Rhine is mostly still one of the most scenic rivers you will find anywhere. There are still a fair number of castles (mostly rebuilt), and I find Andernach one of the more interesting towns on the Rhine. If you had to prioritize, yes, I would probably choose the Koblenz to Bingen stretch, but with a little more time, I wouldn't ignore the section north of Koblenz to Bonn (or south of Bingen to Wiesbaden) either.

Thanks y'all! This has been a very informative and helpful experience!