Silver Duck -- Thanks for the coordinates, but I did already get the electronic waypoint file from Bizer, which is excellent. I especially like the "safe area waypoints" such as east of Little Mark, off echo point, off the east end of Rattlesnake, etc.. The marker I'm refering to is off the "Alton bay" side of Treasure Island, and is a black marker. It is actually quite a way off the island, and at night can be troublesome to spot.
It's just that during the day, I see the marker and don't give it a thought. Later on that night, however, I'm asking myself "Self, why didn't you mosey up to that black spar and make a waypoint??????" Self says I don't want to know why!!!!!
Anyway, thanks for your comments, and safe boating to you and everyone else.