Hello Bob. The nice gentleman who led me through the Stephan Jantzen said to me that it is rebuilt Jumo diesel engines, with 10 cylinder counter-piston. But I'll probably go to Rostock in one and a half weeks again and then I interview the nice gentlemen to their machines.
Best regards
Eckhard

Presumably these are the icebreaker’s three, somewhat-unusual and old-fashioned, American-designed, 10-cylinder, two-stroke, opposed-piston, Fairbanks-Morse 10-38D8-1/8 diesels with a combined output of 5,400 bhp. They were built somewhere in the USSR back in the 1960s