Hi Dockhead, welcome to our cruising grounds! Choose the Länsisatama (Western Harbour) for Your stay as it is better suited for bigger Yachts than the eastern one.
I'm afraid You cannot find tax-free diesel at the marinas
(Itäsatama and Länsisatama) as it is illegal to use in boating
purposes. Road side gas stations will sell red diesel as it is allowed for agricultural use. If I remember right You could find red diesel in Sweden
in Dalarö, some 40 to 50 miles to the south from Stockholm. It is a very small but beautiful marina.
Those Finnish fuel prices are in the mid range compared to Swedish, Denmark
and German fuel prices this summer. The highest price
I paid during our Around the Baltic cruise
this summer was in Sweden at 1,75 euros per litre.
Swan 431 "CAID"