Fuel consumption 2018 CB31/Volvo D4 300hp

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Marnis

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Fluid Motion Model
C-302 SC
Vessel Name
Sonny Side Up
Could you please tell me what the approximate speed/rpm to gallons per hour fuel consumption is? What is the maximum efficient speed/rpm to get the maximum fuel consumption?
Thanks,
Marnis
 
Marnis, are u seeking most efficient speed vs fuel burn? Max fuel consumption is at max rpm


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Thanks for responding. I am trying to find out the best speed cruising speed that provides the least use of fuel.
Thanks
 
Marnis, We have the 2016 model of your boat. If looking for maximum fuel efficiency slower is better. We typically run around 1400 rpm which equates to around 6 kts. Depending on tides and winds that usually gets us somewhere around 5 to 6 mpg.
 
 
Marnis":f18dex7b said:
Could you please tell me what the approximate speed/rpm to gallons per hour fuel consumption is? What is the maximum efficient speed/rpm to get the maximum fuel consumption?
Thanks,
Marnis
Click to expand...

As the charts above show, its a trade off. If you only care about fuel burn or just have the time, then just go slow! If you are pressed for time (and you are in inboard diesel, the OB planing hulls are different) it makes more sense to go around 14 to 15 knots. At 9 to 11 knots you are in the hole and at the least efficient speed (if you care about the time to get there!)
 
Red Raven":243zmfsv said:
Marnis":243zmfsv said:
Could you please tell me what the approximate speed/rpm to gallons per hour fuel consumption is? What is the maximum efficient speed/rpm to get the maximum fuel consumption?
Thanks,
Marnis
Click to expand...

As the charts above show, its a trade off. If you only care about fuel burn or just have the time, then just go slow! If you are pressed for time (and you are in inboard diesel, the OB planing hulls are different) it makes more sense to go around 14 to 15 knots. At 9 to 11 knots you are in the hole and at the least efficient speed (if you care about the time to get there!)
Click to expand...

Dale 777 very nice job on the charts. Your charts are very close to Volvo's D4 specs RPM to GPH.I used Volvo's D3 Specs as a comparison to my findings also close. I'm starting to like your theory Curt. I have tried all different Rpm ranges to find the sweet spot on speed and fuel economy.There is a fine line on rpm ranges on Cutwater 26. SOG-mph and RPM of engine is what I use then watch GPH. 700 to 1500 is great fuel economy but at best max speed is 5 mph. 1800 to 2050 is my best slow cruise speed giving a average of 7.5 mph burning 2 GPH 3.75 MPG. I play around in this RPM range to fine tune rpm to GPH speed doesn't really change. At this speed the boat is running level minimal wake, swim platform is not dragging. From 2250 to 3000RPM there is a 2 MPH increase and a lot of fuel use. 3250RPM is my fast cruise 13 mph 7GPH 1.86 mpg. 3500rpm 16.5mph 8.5GPH 1.94 MPG Better fuel economy better ride and in long open runs get there faster. My issue on this is engine longevity running the engine at just under 90%. Most say 80%. Opinions on this ??? All my numbers are averages over a season of running. The 1800 to 2050 and 3250 RPM are good averages because most of my cruising was done at these ranges. All sea conditions are averaged in these numbers. I will note that my numbers are better in the beginning of the season when it is cooler out and get worse as the summer heat comes in. I actually noticed a 6% loss in fuel economy in August last season. I thought it was growth on the bottom so I pulled the boat to clean the bottom. It was clean a little green on the top of my tabs and top of stern thruster that was it. My conclusion was engine compartment temperature. I found thru research that the ventilation of the compartment is marginal at best. I will post my numbers and solution in a different post when completed.
Brian Brown
Cutwater 26
PORT-A-GEE
 
The chart below shows what I mean by least efficient between 9 to 11 knots when considering time. This data is straight from the RT performance charts with the exception of the upper line. The upper line is mpg multiplied by speed which I like because it includes time, distance and fuel. MPG only includes fuel efficiency relative to distance traveled so it may look real good but may take to all day to achieve. Gallons per hour is missing distance so you can tell if you are getting anywhere for all that fuel!

A similar chart could be created using the factory R31 data.

Curt

 
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