I can't comment on the Marlin 7 but I have the Marlin 6 . I don't use mine in the mountains, but instead on local rather flat trails and backroads.
Mt Marlin 6 would be on the heavy side but it carries that weight quite well. Mine has never give me any problems with shifting or braking. My Tectro Hyd. brakes are beyond dependable. The best description I can give of them is that I don't give them any thought. I know they will be there if I need them. The gears are displayed in a window , and that helps if I let a newer rider try it out. Mine is 5 yrs old and I think I gave near $600 new.
I have changed the pedals for cheap flats. and at present trying a set of Kenda 700 X 42c . They seem to ride as smooth as as the original 29" tires I wore out.