Re: 140 Mercruiser outdrive noise
check the oil in the drive. Is the level correct and is there any water or metal in the oil. It would look a little like metallic paint. If thats ok, pull the drive. Inspect the ujoints/gimbel/bellows. If all that looks ok, you can start inspecting the engine. I would start with a compression test. A little more background/history on the boat would help, along with a complete description. year make model etc...did it start suddenly? Have you ever seen it run like it should?
