The original mixing elbow on the engine was a cast iron type with a large stainless steel nipple that had both right and left hand threads. The nipple connected the elbow to a cast iron exhaust flange. The elbow required two extra large gorillas to work on and was prone to corrosion in and near the water injection port.
While in Marathon, Florida several years ago I walked across the street to pick up a new elbow and the Yanmar parts lady told me about the new elbow and I bought one.
I also needed a 3″ to 2″ fiberglass exhaust reducer and a short piece of 3″ wet exhaust hose as the boat exhaust system used 2″ hose but the new elbow has a 3″ exhaust port.
The reducer coupling that I used is made by Centek: Part number 1200264
Yanmar Part numbers