Drip from behind impeller

I noticed a small drip from the impeller, so I checked it and it is fine. I tightened the brass fittings and the Allen bolt on the bottom and there is still a tiny drip coming from the rear of the housing. Is this where the lower water pump is located, and is this indicative of a more serious problem? I replaced the upper pump years ago and regularly replace the impeller if any 'legs' are broken or missing.

Thanks

Drip got worse under load. Ordered a new raw water pump and will install it today. Getting the old one off was no picnic.

My 2001 did that several years ago. Was a small o-ring in the back of the housing. Discount Inboard Marine diagnosed it and sold the part.

Thanks. When I took the old one off it rotated freely, which it isn't supposed to do. New one from Michigan Motors works like a charm. Fairly easy install.