As mentioned above, this most certainly looks like a failed prop shaft seal.
Just out of curiousity, what would be the problem with leaving the lower end without oil over the winter. Not that I’ve personally done it, I think one time my bottle pump broke so I was stuck for a day with no oil, but just curious as to why a sitting motor lower end that obviously still got a film of oil all over it would be damaged by sitting for a couple of months with no oil.
either way siwash, lesson learned, at minimum undo that screw at the end of the year, no matter what get the years gear oil the hell out of there even if it’s nowhere near as watery as this. Being fair this is some of the worst looking oil I have ever seen, that crank case was completely full of water as far as I can tell. You may get really lucky and have no other damage. My buddies merc used to leak water too not anywhere close to this extent but if you’re lucky the water didn’t expand and crack your Lower end. if you’re like my buddy you might get away with it for a year.
this kinda stuff haunts me when I think about the fact my boat is used, who knows what kind of maintenance or lack thereof people do at the end of the year. I’m not as much of a nutcase to be changing my prop shaft seal every 2 years as referenced above, but I sure as hell change the lower end oil, fog the motor, change fuel filters every 100 hours, stabilize my ethanol free fuel etc etc
hopefully worth it in the long run, high performance engines ain’t cheap in 2023!