By the way, my 14 year old son and I rode from the Skyview Lodge (in Presque Isle, WI - about a half-hour ride from Mercer) to the Mariner North in Copper Harbor and back last winter. We left the gas station in Presque Isle at 9:00 AM and reached the top of Brockway Mountain overlooking Copper Harbor at exactly 5:00 PM. We never went over 50 MPH (as I had a youngster with me, even though he rides as well as any adult). We stopped for lunch at about 1:00 PM at the Parkview in Twin Lakes and rested until about 2:15. We then continued with a few short stops until we reached Brockway Mountain. Mileage was about 170 miles from Presque Isle to Copper Harbor. The trails were impeccable - we hit only one stretch that was bumpy and it lasted less than five miles. Otherwise, everything we rode on was board flat and very nicely (and recently) groomed. The return trip was just as nice - although we added a few miles on the return to go through the Cisco Chain for a dinner stop at Bent's Camp.
We stayed in a really nice cabin at the Mariner North (they were sold out of hotel rooms). I would say that the loop from Houghton/Hancock to Copper and back would be close to 70 miles. You might be pushing your luck by planning to ride from Mercer to Copper Harbor and back to Houghton in one day. I wished we had planned for a second day in Copper Harbor, because there are several really beautiful loops you can ride up there and the snow is just incredible. Grooming last year up there was nothing short of spectacular (with the exception of a five mile stretch area just north of Calumet, which didn't seem like it had been groomed for some reason). You can stay in Houghton at the Radisson, which really caters to sledders, but I found the accomodations in Copper Harbor (the Pines and Mariner North) to be very nice as well. (Great breakfast at the Pines). I can always stay at a Radisson, but I rarely get to stay in a real northwoods lodge. I've attached some photos from the trip.
Just North of the Bridge:
Junction of Trail 3 and Trail 134 (where Trail 3 breaks off to the North to Copper Harbor):
Dusk on top of Brockway Mountain (wind howling - note the lack of snow):
Overlooking Copper Harbor on the way down from Brockway:
Breakfast at the Pines Resort:
Returning through Houghton/Hancock:
It was a great trip. I hope to do it again soon.