Hi Peter, I had a W 4-107 on my prior boat. It had an exhaust elbow made up of galvanized pipe, the type you can find at a hardware store. When it finally rusted out, I replaced it with bronze pipe of the same type. Where the raw water gets injected, I simply drilled the pipe and inserted a bronze nipple which could be either threaded or glued in with JB Weld, which is what I did. It was still going strong 10 years later when I sold the boat.