I am losing drive fluid from a Merc #5. The drive is not overfilled. The leak isn't from an obvious location or I wouldn't be writing this post. It does appear to be coming from the vent tube. I only think this because there is some oil high on that side of the transom. The other side seems fine. The amount of fluid loss is about 6 ounces. It always looks worse because of a little water in the bilge making the oil volume look greater. Any ideas or has anyone else experienced this? Thanks!!!!

Don't know about number 5's, but with b-1 reservoir they will leak under way if the o-ring inside cap is missing or if the cap is cracked as there is some pressure present.

Thanks Wobble, but the #5's have a bolt instead of the cap used on a bravo. Again, thanks.

Please explain as I seem to be having this problem. TIA.

B-1 drives generate a small amount of pressure when they are running. The cap on the reservoir has an rubber washer inside the cap that ensures a good seal. If this washer is missing or the cap is cracked you will probably spill drive fluid out. The cap helps maintain a little pressure which helps reduce aeration of the oil.

Thanks.