No, if there is some water in the LU you will see white to creamy streaks in the oil or as I had recently liquid that looked like cream of mushroom soup. Not a good signIf there is oil in the lower unit it should appear milky correct? No oil has needed to be added but I haven't ran it hardly.
I had 2003 F225s on my Marlin. I dropped both lower units and scoped the exhaust tube. Both had corrosion. My marina replaced both with a kit from Sim Yamaha. One engine had beginning of corrosion on the bottom of the oil pan. It was cleaned, repaired with a weld and checked a year later. All was good. I replaced both with new Yamaha F250s in 2020.F225 model (4 stroke) I'll keep posted.