Hi Rocketman,
A few questions:
Can you see water dripping from the stern gland? Try placing a container under it like an old ice cream tub. See if the puiddle still appears.
Modern stern glands, unless they are of the sealed kind, dont rely on grease. Those mostly used on narrowboats have gland packing (a kind pf greasy rope) which squeezes tightly around the shaft. They have a way to tighten them, either nuts & bolts or screwed rings
Are you sure that the water is not leaking coolant? Is the level going down in the header tank? Dip your finger in the puddle - does it smell sweet? If you are brave taste it. If sweet it will be anti freeze. Beware though ant freeze is toxic.
Do you have a bildge pump? If so set on automatic.
The stern gland is where the prop shaft exits the interior of the boat through the stern post. The prop is on the other (wet) side.