TRAVELLING RHINE TO KOBLENZ, KD BOAT,TIME TO STOP IN ONE TOWN AND HAVE LUNCH, BOPPARD OR ?
WAS GOING TO STOP IN ST GOAR, BUT HEARD ROAD CONSTRUCTION IN TOWN/
You don't say where you're STARTING the cruise. Boppard is quite nice. But so is Oberwesel, and Bacharach too, if you happen to be passing them. It's actually not easy - or even advisable - to continue by boat from Boppard to Koblenz. Let's say you're on the absolute earliest boat from Bingen at 9:30 and reach Boppard at 11:50 for lunch. The next boat is at 12:50. But if you want to visit a winery or take the chairlift ride or see or do anything else in Boppard, or even just have a leisurely lunch, you won't make that boat, and then there's no other boat until 16:00! And after Boppard, the scenery is really just so-so except for Marksburg Castle; it becomes downright industrial around Koblenz, so why bother? And if you end up at the Koblenz dock, you then have a long walk to the train station if you're headed elsewhere. Just end the cruise in Boppard and catch a train from Boppard to Koblenz if that's where you want to end up - it takes about 15 minutes instead of 1 hour 20 minutes, the fare is 5.60€, you will see Marksburg Castle from the train window, and the cruise fare to Boppard is 10€ less than if you cruise to Koblenz.
We took the KD Rhine from Bingen to Koblenz back in 2009. We were on the Dusseldorfer. We had a lovely meal right on the boat as we watched the scenery go by. Here is the schedule if you don't have it already. If still possible, a meal on the boat might be fun if your only reason for stopping in a town is to have lunch. That particular ship was mostly a restaurant!
You said you will be traveling Rhine to Koblenz which leaves no starting point. Did you mean to say Rhens to Koblenz?? If Rhens is the case, I would have lunch on the boat and watch the scenery go by. Rhens is north of Boppard and there isn't much between there and Koblenz.