should be a o ring under that brass sleeve
changing the oring is not so bad…………….. lots of Utubes on it
me….. I used the tap and rod method with a block of wood worked great on my oldies
https://www.bing.com/videos/search?q=ut … &FORM=VIRE
if oil is not recent and… remains waterless maybe you should NOT FIX IT for now
clean out that L’/U cavity that drain hole should drain. I cleaned out a Merc 4hp with sand and crud an inch thick down that cavity
Joining AOMCI has priviledges 🙂