Any suggestions for hotels in this area of the Rhine?
Start off by learning how to spell the names of places to which you want to go. (But, in your defense, your spelling of Boppard is closer to the actual pronunciation.) Boppard. Bacharach (Baccarat is a card game). Boppard's website lists some fine hotels (not the cheapest) on a road facing the river. I would particularly recommend the Best Western Bellevue and the Rheinlust. Boppard is well situated between Koblenz and Bacharach. In Bacharach, although I have never stayed there, if I were to, I'd opt for Im Malerwinkl.
Catherine, I can't provide any information on Boppard, but in Bacharach I'd highly recommend Hotel Kranenturm. Although they're right next to the tracks, I didn't have any issues with train noise, even though I was there for almost a week. The restaurant there is excellent! If you'd prefer more of a B&B you could also have a look at Pension Lettie. It's not far from Kranenturm and I found the rooms to be clean and comfortable, and Lettie is a wonderful host. If you're planning to travel in the early spring, I'm not sure whether Pension Lettie will be open. You'll have to check with her. Happy travels!
We stayed at the Hotel Zur Loreley in St. Goar for five nights, renting one of their apartments and found it very nice. From there we were able to travel up and down the Rhine on both banks, as a ferry crosses there every fifteen minutes.
One thing to say for St. Goar is that it is in the VRM (Verkehrsverbund Rhein-Mosel), which includes everything on the Rhein from Oberwesel down to Remagen/Linz; Bacharach is just outside the Verbund. VRM sells day tickets (Tageskarten) for the entire Verbund for 18€, single, or 21,20€, up to five, but I don't think you can buy them in Bacharach. That makes St. Goar a better base for exploring the Rhein from Oberwesel down, because you can just buy your Tageskarte at the station and go. From Bacharach, you'd have to buy a ticket to Oberwesel (2,30€) or St Goar, get off there, buy the Tageskarte, wait for the next train in an hour, then go.
Catherine, We have stayed at Im Malerwinkel several times and have been very happy with it. It is an easy walk from the train station and they have parking available if you are driving.