Boatingfool
New Member
This is something I've been debating for a while...I am better trying to understand the "best" crusing speed for my boat and hopefully this will be fuel for thought for anyone else who has larger engines and is wondering how to maximize their fuel consumption.
The manufacturers typically (especailly MAN) publish the engine output (horsepower & torque) at "Full Load".
The Fuel Consumption is published at "Propeller Demand".
So my hypothesis is this... theoretically you may use 100% Load to get up out of the water, but as the boat planes the water resistance of the boat should decrease slightly. Becasue this load decreases, the load on the engine should decrease. This decrease in engnie load should causes the engine to burn less fuel at a given RPM.
I unfortunatley do not have a load meter on my electronic diesels.
So, the question for those of you who do have fuel flow & load meters, have you compared what your Fuel Consumption the gauge tells you vs. the Fuel Consumption listed on the diesel manufacturers data?
And, once you are up on plane does the boat run at 100% load or does it back down to say 70-80% load?
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What am I trying to establish? How much load decrease, if any, you see to help me better understand the correlation between the published fuel consumption data.
The only reference point I currently have is that the MAN literature says the engines consume 84gal hr. at Propeller Demand @ 2100rpm (which gives me 30-31knots). Sea Ray says their recommended crusing speed is 2100rpm (they say 35mph) and at 2100rpm they say the engines are burning 68gal hr.
The manufacturers typically (especailly MAN) publish the engine output (horsepower & torque) at "Full Load".
The Fuel Consumption is published at "Propeller Demand".
So my hypothesis is this... theoretically you may use 100% Load to get up out of the water, but as the boat planes the water resistance of the boat should decrease slightly. Becasue this load decreases, the load on the engine should decrease. This decrease in engnie load should causes the engine to burn less fuel at a given RPM.
I unfortunatley do not have a load meter on my electronic diesels.
So, the question for those of you who do have fuel flow & load meters, have you compared what your Fuel Consumption the gauge tells you vs. the Fuel Consumption listed on the diesel manufacturers data?
And, once you are up on plane does the boat run at 100% load or does it back down to say 70-80% load?
****************************************
What am I trying to establish? How much load decrease, if any, you see to help me better understand the correlation between the published fuel consumption data.
The only reference point I currently have is that the MAN literature says the engines consume 84gal hr. at Propeller Demand @ 2100rpm (which gives me 30-31knots). Sea Ray says their recommended crusing speed is 2100rpm (they say 35mph) and at 2100rpm they say the engines are burning 68gal hr.