DonF
Member
Here is a link to a Google sheet that I am in the process of putting together for my own use.
https://docs.google.com/spreadsheets/d/10LSPwtcHriXjG0S1mTsCLHgYrC8M56fwN7GFWngMUfA/edit?usp=sharing
Some of the data comes from the Factory specs, some the Sea Trial, and some from my very limited experience with the boat (purchased it August 18, 2016). I hope to update the Factory hull speed in the next few days. Then I will see if the over propping might have given better fuel economy. If it doesn't I may switch back to the original pitch to lower my idle speed and let the engine run a little easier (less fuel per cycle for a given hp).
I used the prop loading curve for factory fuel curve. Right now my fuel consumption is my best guess. But it matches the generic formula for fuel consumption at hull speed pretty well.
Hull Speed knots (sqrt LWL * 1.15)
For my boat this is 6.1 knots
(Disp in metric tons * 2.5) Boat weight loaded / 2240 * 2.5 = hp required @ HS
I used 20500 lbs for my boat (full fuel and water tanks) Boat empty weights 17500 lbs I think.
For a single Diesel HP per Gal = 18.
I've seen numbers from 15 to 18 for this calculation. The 18 HP per Gal seems to fit my boat pretty well.
I would welcome any comments, questions, or corrections.
Hope someone finds this a little useful.
Also note that my prop has 4" more pitch than the original prop hence the lower max RPM from the factory specs.
https://docs.google.com/spreadsheets/d/10LSPwtcHriXjG0S1mTsCLHgYrC8M56fwN7GFWngMUfA/edit?usp=sharing
Some of the data comes from the Factory specs, some the Sea Trial, and some from my very limited experience with the boat (purchased it August 18, 2016). I hope to update the Factory hull speed in the next few days. Then I will see if the over propping might have given better fuel economy. If it doesn't I may switch back to the original pitch to lower my idle speed and let the engine run a little easier (less fuel per cycle for a given hp).
I used the prop loading curve for factory fuel curve. Right now my fuel consumption is my best guess. But it matches the generic formula for fuel consumption at hull speed pretty well.
Hull Speed knots (sqrt LWL * 1.15)
For my boat this is 6.1 knots
(Disp in metric tons * 2.5) Boat weight loaded / 2240 * 2.5 = hp required @ HS
I used 20500 lbs for my boat (full fuel and water tanks) Boat empty weights 17500 lbs I think.
For a single Diesel HP per Gal = 18.
I've seen numbers from 15 to 18 for this calculation. The 18 HP per Gal seems to fit my boat pretty well.
I would welcome any comments, questions, or corrections.
Hope someone finds this a little useful.
Also note that my prop has 4" more pitch than the original prop hence the lower max RPM from the factory specs.