Engine oil should not get to the transmission, and past the stuffing box (not on a working engine.
Remove the waste water and oil from the bilge.
Go sailing again (that's the fun part), leave the motor in gear - depending on your religious affliation, time of month, gender and day of the week (except tuesdays) either in forward or reverse.
Check the bilge, if empty congrats you have fixed it. If not and it's black again you have stuck oil (with a name like Chevon what did you expect) or you sail in the Chesapeake and it's normal water.
In either case you should not be getting that much water in around the gland (a bilge full on a day trip).
Did you forego repacking the stuffing box this past off-season?