Why are you going to all of this trouble? Indmar's instructions for winterizing the engine are to drain the block and manifolds and leave the plugs out. I do that plus drain the shower and heater, lubricate the threads so that they will not rust and have never had any problems. I get 2 or 3 good freezes each winter and store the boat outside. Not only is it just as fast if you are doing a total winterization but you do not have to dispose of any anti freeze. Even if it is biodegradable you can't just dump it into the lake.