Cloudy sap can be a result of the weather turning warmer or the sap sitting unprocessed a little too long. Bacterial growth can cause cloudy sap, which can have an undesirable effect on the syrup's color and taste. Smell and taste the sap, and if it tastes ok then go ahead and boil it down. It will most likely make dark syrup. It's important to keep the sap cold and don't wait too long before boiling it down. Sap can spoil and become cloudy and off-tasting if it is left too long in storage.