I had that happen on several motors of different brands in the past when the lower unit was exposed to direct sun light. The heat will build up the pressure beyond what the seals can hold and release a little. I do have a 90 E-Tec and that happened a couple months ago on mine. I checked the oil and everything was OK. I have been having it since August 2007. I changed the lower unit oil and there was no water in it. I know they say that you don't need to change the oil for 300 hours, but it is my motor after 300 hours and I will change it every year just like I have always done.
There is an E-Tec web page that you can post this to and get very good answers.http://forums.etecownersgroup.com/mb/barnaclebill
I would still check it out by opening the bottom drain screw just a little to see if any water will come out and that the oil is not milky showing water in the oil. The oil coming out of that hole looks good.