1 & 2: red funnels, steam-packet.com on the hull
3 & 4: blue funnels, superseacat.com on the hull
Saltydog is Close enough. I was looking for the fact that SSC 1 and 2 have small funnels:
http://www.faktaomfartyg.se/superseacat_one_1997_b_9.htm (http://www.faktaomfartyg.se/superseacat_one_1997_b_9.htm)
Whereas SSC 3 and 4 have big funnels:
http://www.faktaomfartyg.se/superseacat_three_1999_b_1.htm (http://www.faktaomfartyg.se/superseacat_three_1999_b_1.htm)
Diamant, thanks ofr that bit of info about the number of bowthrusters, I hadn't noticed that before.