Oil and Water

[Blue-Skies]

A few months ago, I purchased a pontoon boat with a 2007 Mercury 60 HP EFI outboard. Only used it a few times and it ran good. Decided to do the right thing and "winterize" it by changing the engine oil and gear lube. When I pulled the oil drain plug, the stuff that came out did not look like oil. I expected black gold but it was more like Nestles chocolate milk. That means water is getting in somehow. I went ahead and changed the oil filter, put the oil plug back in, and filled it back up with fresh oil. I hooked a hose up to it, started it, and let it run for about 45 minutes. After shutting it down, I pulled the dipstick to see if the oil turned to chocolate milk again. It did not! Granted, it was just idling at about 800 RPM with no load so I don’t know if that was a good test. Does anyone have any thoughts on what to do about the issue?
Thanks
Greg