From what seems to be a 1998 abstract on retrofitting the main engine of the Japanese vessel Fukaemaru come these two Sankey diagrams. Found this on the website of the Kobe University Martime Faculty. Both nice plain black&white.
The first one shows energy efficiency of the original gas turbine equipped machine room. The base seems to be 100% energy (the label actually says ‘fuel exergy’) and the useful energy (arrow going straight up, labeled 出力) is 15.48% only. Losses branch out as arrows to the left and to the right.
The other Sankey diagram shows the energy flows for a diesel powered main engine. Efficiency is up to 37.38%
On a side note: funny to see that in the description of the figure at the bottom the author actually turned “Sankey Diagram” into a “Keysan Diagram”…