Wash sweet potatoes and pierce each one a few times with a fork, then wrap individually with foil. Bake for 40 – 50 minutes, or until soft. Reduce oven to 350F, allow potatoes to cool slightly, then slice each potato lengthwise. Scoop out a small amount of the inside of the potato, leaving about 1/3 -1/2 inch of potato along the sides and bottom of the skin. Place your 4 sweet potato boats back on baking sheet, face up, and bake for another 10 minutes.