Drained lower unit on 86 25hp Evinrude, old came out milky so I know there was water in it. Left it in NY for the winter and always drain and refill. Never any problems. 96 40hp Yamaha? I have owned this 5 yrs and never changed the fluid cause it stayed in FL. Left that Boat/motor in NY this year. Old fluid was clean but Black. Filled with new lower unit fluid that I have used for years in Evinrudes and Mercuries. I will check it when I go up in the spring but Does Yamaha have their own brand of lower unit fluid?