Fuel consumption..

[Tranona]

Back home from my sailing trip.
Here is my performance graph:

Speed is more or less linear since for a fixed pitch propellor engine revs to speed should be linear. Fuel consumption increases dramatically at higher revs - I'll bow to other wisdom that it is a cube curve.

Consumption is a function of power used over time, not distance travelled, either through the water or over the ground. Distance travelled is affected by sea conditions and tide stream.

You can correlate the two (time and distance) in flat conditions and no tide but as soon as you introduce adverse weather conditions speed falls for given power, and if you have tidal streams for or against speed over the ground (and therefore distance travelled) will increase or decrease.

 

[V1701]

About 1l/hr from Beta 14 not flat out so yes 1l/10hp/hr works for me...

 

[reeac]

I have a Vetus catalogue which contains data regarding their whole engine range and, as a broad rule of thumb, smallish diesels consume 0.18 to 0.2 Kg. of fuel per bhp.hour when run at optimum speed. Density of diesel fuel is 0.83 Kg./litre so 0.2 Kg. represents 0.2/0.83 litres i.e. 0.24 litres or 0.053 gallons. Thus it's 0.053 gallons per bhp.hour which is 18.9 bhp.hours per gallon.[ Hence the time-honoured 20 bhp.hours per gallon]. This figure [0.24 litres] is very different from Tranona's 0.1 litre per bhp.hour and I can only guess that the difficulty lies in arriving at the figure for actual power consumed by the gearbox and prop.