For your informations.
On my GB 52 at Max weight (33 tons)
with my 2 QSL9 405 HP
At 1100 RPM 8,2 knots 7,8 liter/hour/engine
At 1200 RPM 9 knots 8,8 liter/hour/engine
At 1400 RPM 10 knots 18 liter/hour/engine
At 2150 RPM 17 knots 96 liter/hour/engine
At medium load (with only 2000 liter...