Baked Potatoes Cooked Over a Fire This weekend, my wife and went camping. I tried to impress her with a surprise meal (much more than the usual smokies or hotdogs roasted on a stick). I went for steak, potatoes, mushrooms, salad and a corn on the cob. Everything turned out great --- except for the potatoes. 

ISSUE

Potatoes were only cooked after 4 hours in the coals. 

TECHNIQUE

Got the fire food and hot (at least 350F, used an infrared thermometer to check). I put the potatoes (Yellow, baking potatoes if it matters) in the hot coals. I have made them like this before, and it typically took 2 hours. And I rotated them periodically (so as to not let the foil burn from prolonged contact). As I mentioned above, I've made potatoes like this before...but never had them take so long to cook. 

By the way the rest of the food turned out just fine (actually better than fine, it was the best back country camping meal I had ever made). We ended up using the potatoes for hashbrowns the next morning because we didn't want to wait for them to finish before making/eating the rest of the dishes.

QUESTION

Given the above technique, why did my potatoes not cook like they should.
Two likely possibilities:


The potatoes had too much foil surface exposed and not enough in contact with hot coals, and as a result were just not getting hot enough.  Maybe it was a colder night (were you hiking at altitude?) maybe the coals had a lot of insulating ash, maybe the coals were already too cool (350F is not particularly hot for coals).   This is why burying the potatoes in the coals is more common.
The potatoes you bought were defectively dense.  Apparently potatoes can have a growing problem where the core of the potato is extra-dense due to weather changes, and that core takes forever to cook through.