Re: Lower unit oil is Milky.
Unit may develop a slight pressure/vacuum as it cools/heats up, which allows water in when you have a bad seal. I'd pressure test the lower unit. Drain the oil and pressure test with lower unit on motor. Pressure tester available on Ebay for about $30. Pump it up to about 10psi. See (and hear) where it is leaking - spray a little dish soap solution on prop shaft, drain and vent bolts, and the little phillips screw on the lower unit. If it bubbles or hisses, it is leaking. Hopefully, it is only a nylon washer on the drain or vent bolt. That's easy to fix. Next most likely candidate is the propshaft seal - fishing line gets tangled around them and compromises the seal. There are also seals at the upper driveshaft and the shift rod, which can only be fixed by pulling the lower unit.
