The units have to cancel so it looks like division is what you need as you showed in the example. I'm not sure about the multiplication by rated power however - do you really use that or is it a maximum value?

 

You have it correct. Multiply by the power in kW then divide by the density in g/l. Note that you if you want consumption at other than rated power, use the actual power and the fuel rate at that power. The fuel rate will vary somewhat with power, though not much once above about 1/3 rated power.

 

thanks for your reply. you are correct should be

g/Kwh x engine kw : density of fuel (0.85 for diesel)

one more "question".

can i install 100 US gallon tank in the 20 foot boat. ofcourse, i can. but should it be overkill. engine is FNM HPEP-150 sterndrive. what would be bigest tank that i normaly can install in boat this size. i would like to have as much range as posible.

i am in europe and would like to cruise med, croatia to greece, sicily, etc at least 300 miles range with 10% reserve fuel

thanks one more time.

(sorry for english, it is not my first language)

this is the boat...

Overall Length 20' 3"

Overall Beam 6' 10"