HEre's another data point:
In Insatiable one, a 36 ft ex IOR one-tonner with a 35 hp BMW we logged an average of around 300 hours per year, full time cruising. During those 17 years we did 86,000 miles. That
engine consumed around 1.5 to 2 l/hour depending on how dirty the bottom was and so on. So, <600 litres per year. No gen set, but some
charging using the main engine (small
solar plus at-anchor
wind gen).
Since we
sold I-one and bought I-two (46' performance type
boat, 43 hp Nanni, no gen set,
diesel heater, adequate
solar for most places plus Air-X wind gen) we have done slightly less miles/year: 39,800 in 8 years. Still use the engine around 300 hours/year, but this one uses 2 to 2.5 l/hr, so we use around 6 to 700 litres per year, including some
heating.
Our sailing style emphasizes sailing over motoring, but when cruising the
East coast of
Australia there are lots of barred entrances that require timely arrivals, and so we find we
motor somewhat more there than in general.
Hope that this helps in your decisions .
Cheers,