It is most likely the shift rod bushing at the top and in the front of the lower gearcase.

The lower housing will need to be removed to replace this bushing. Would you like assistance with the removal and replacement of the seal?

No, it is very likely gear oil and if it is the most likely source of the leak is the shift rod bushing and seal. I have attached a diagram of the lower gearhousing. The component I am speaking of is #35 along with seal #36. Very common issue with mercruiser lower gear oil leaks.

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You can do the job if you're handy. There are no special tools involved.

1. disconnect the speedometer tube at the front of the lower gearcase
2. Remove the propellor
3. Tilt up the outdrive and begin by removing the (4) nuts on either side of the top of the lower housing.
4. next, at the rear ot the outdrive you will see a plastic cap covering a small hole above the trim tab. remove the cap, (if it is still there)
5. inside this hole is the bolt holding the trim tab to the bottom of the ventilation plate. Loosen this bolt and the trim tab will come off
6. just in front of the trim tab recess there are two more nuts that you need to remove
7. the lower unit will slide off and you can put it between a couple of blocks so you can now work on the shift rod bushing.
8. You will see a small hole in the upper gearcase where oil will begin to drip from. A golf tee works great to plug this while you have the lower off.
9. the shift bushing is located on the very front of the lower gearcase. I suspect you will see gear oil at this area.
10. Replace the bushing assembly I pointed out in the earlier diagram.

Do not turn or rotate the shift lever at the front of the housing.

You are now ready to reinstall the lower.

While holding the lower unit up to the upper housing make sure the water tube lines up and goes into the one in the upper housing and also make sure the shift rod goes into the shift lever in the upper housing. You can watch both while you are reinstalling the lower unit.

Replace all the nuts and the trim tab (use locktite on the trim tab bolt and make sure it is tight)

Check the gear oil level before running the engine and fill from the bottom hole if it is low.

You are ready to go boating again.