Re: Lower unit oil is black and smells
I've read that some outboards tend to "stink up" their lower unit oils, but when I drain my 90C Yamaha lower unit the oil comes out just like it went in, sorta clear and honey-colored, without an odor. If you had water leaking into your lower unit due to a bad seal your oil would be milky looking. Are you using the specified "Marine Lower Unit Oil"? Are there any larger metal particles on the drain plug magnet? I doubt there's a problem there, but it might make you feel better to change your lower unit oil more often, like twice a year?
