Here's what I ended up with. (I forgot the rum) It turned out really good, and it used up that can of yams. I tasted the juice from the can and it wasn't something you'd want to use; I poured it out.
Sweet Potato Pie
1 (10 inch) unbaked pie crust
3 eggs
¾ cup brown sugar
¼ teaspoon salt
1 teaspoon vanilla extract
1 (12 oz) can evaporated milk
1 (29 oz) can cut yams (sweet potatoes) in syrup, drained
½ tsp cinnamon
½ tsp ginger
¼ tsp mace
¼ tsp black pepper
nutmeg
Freeze pie crust at least 30 minutes. Preheat oven to 450 degrees. Put eggs, sugar, milk, salt, spices except nutmeg, and sweet potatoes in a large saucepan. Blend with a stick blender over low heat until smooth and warm. Pour filling into frozen crust and grate a little nutmeg over the top. Place on center rack in oven and bake for 10 minutes. Turn oven down to 350 and continue baking for 30 to 40 minutes, or until a small sharp knife inserted in center comes out clean.
Notes: This is a big pie; it takes a 10” pan or a 9.5” extra deep pan. I combined Maida Heatter’s pumpkin pie recipe with a vanilla custard recipe, then substituted in the sweet potatoes without really knowing what I was doing -- and it worked. Next time I might try cream instead of evaporated milk.