That sounds like a head gasket and/ or a cracked head. You can change the gasket first if it's not too much and that may be it, or you could get the head magnafluxed and checked with a machinist strait edge while it's off.
wayne…….I agree with tinbender. I would suggest to take the head off and visually inspect the gasket and head. If its burning coolant bad enough which it sounds like it is, you should be able to tell what cylinder or cylinders its burning out of. The top of the piston will be cleaner or whitish in color on top of the piston. If you don't see anything out of the oridanary, then I would take it in and have the head fluxed or depending on how many hrs are on it and looks bad maybe buy a whole new head if they still make them that is.