I have a 1986 Catalina 30 TRBS with a Universal M25. I was in the engine compartment and I found a hose that was loos and not connected to anything at either end. I did a bit of Google image searching and it looks like it connects to the spot indicated on the picture of my M25. My question is what is that and where do I plug the other end in? It is just a threaded elbow pointing down.