Have a half day tour or taxi service in Helsinki?

Take into consideration when you count the hours you will have, that though your cruise ship arrives at noon, it will be an hour or two before you disembark, and you need to be at the airport with ample time for your 6:00 pm flight.

At which port do you arrive.

There are luggage lockers at the central train station. I’d suggest you travel to the train station, store your luggage, and then spend your limited time walking in the area around the Esplanade and visiting the market in the harbor. This is within walking distance of the train station. If time permits, visit the church in the rock. Alternatively, The RS book describes a tram tour that takes you by city sights.

I used the Finnair bus on my last visit. It departs from outside the central rail station and takes about 30 minutes to get to the airport.

Thank you very much.
Leave the luggages at the central train station and walking to the esplanade is interesting.
Is the Helsinki Cathedral in walking distance? And is there any taxi from the area to the airport?

Helsinki Cathedral is next to Senate Square and less than a 1 km walk from the Central Train Station. After visiting the Cathedral/Senate Square, the open air Market Square is a couple blocks south on the waterfront.

We have taken the Finnair Bus that runs between the airport and the central train station:
https://www.pohjolanliikenne.fi/en/finnair-bus-timetable.html

I understand that one of the train lines runs between the airport and central station:
https://www.hsl.fi/en/timetables-and-routes/terminals/transport-links-helsinki-airport

Line 615 (local bus service) is cheaper than the Finnair Bus but has multiple stops:

Taxis to/from the airport run about 40 or 50 EUR.