Here's a related problem- either a crack or deep scratch along the surface that seats the V-plug O-ring (see attached photo).
Last haul out my oil also came out milky, but the propshaft seals were 4 years past changeout date, so I can't know whether seawater got in under the O-ring via this crack or through the mainshaft seals.
Anybody have an idea for a fix? Fill it with epoxy and sand it fine? Somehow put in a new seating?
Previous owner said "Ignore it, it's been there since 2003." which I find unsettling.