mixing elbow

Hi, I was motoring back from anchoring out and after about an hour I smelled diesel exhaust coming from below. I took a quick look in the engine room and saw it was filled with smoke. I raced back to cut the engine. Once the air cleared, I saw the nipple between the exhaust elbow and the...

This is truly one of the most unbelievable things I have come across in engine maintenance and I wouldn't have believed it, if I hadn't seen it myself. Even at that, I'm doubtful. Several months ago, I pulled the mixing elbow figuring it had three years on it (about 300 hrs) and it was time...