I want to change the antifreeze and upgrade it to ELC. I think I know the proceedure, but I don't know the how best way to drain the old antifreeze. Is there a drain plug, or do I have to disconnect a hose. Also, where are the plugs that I have to open to get rid of air pockets when flushing the system and re-filling it with ELC? The boat is a 43 EastBay with not much space in the engine room.