It may not be the boots. Sounds like your feet are not used to hiking with the weight. Are you using high percentage merino wool socks? With no training, I usually start to get blisters/hotspots around the 6-7 mile mark with a 50 pound pack. This spring, I trained w/ a 50 lb pack for 3-4 months and on my last 27 mile/3 day hike my blisters/hotspots started around 20 miles and when done with the hike they were very minimal.
