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Diesel fuel consumption


Crow
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Hello all ,after removing a 15 hp Mercury  petrol  outboard and installing a 25 hp 3 pot vetus  , mated to a Enfield leg and a 13x8 or 9 prop in my little  25 ft springer. Would you think 3. kilometers  / litre.       Or about  2. 5    litre / hr  is  acceptable or a mile away from what it should be,thanks,Nick.

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How are you measuring that? If its off a test volume    in a test tank the a lot of the has not been burned but leaked back to the boat's tank.

If its fill up, time, refill the main tank then it sounds very wrong to me. Most of us expect between 1 and 2 litres an hour, yours should be at the bottom end of that range.

Is the prop in free flowing water or is it masked by the transom?

How did you arrive at the prop size?

Edited by Tony Brooks
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I've been keeping a close eye on fuel used. Halcyon has a Perkins 4108 and is 36' in length. Recently I've been managing almost 2 miles to the litre. On the recent trips, first to Leeds, second to Boston. I filled up before the Leeds trip and again in Burton Waters marina, I'd used 103 litres and covered 197 miles.

 

Kevin

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Miles per litre seems a bit meaningless to me, perhaps even misleading, since on the canal 3 miles could take anything from an hour to most of the day depending on many factors that see you making little or no progress whilst the engine is still running. Litres per hour is a more meaningful metric, is far easier to measure and is more commonly used.

  • Greenie 1
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20 minutes ago, Sea Dog said:

Miles per litre seems a bit meaningless to me, perhaps even misleading, since on the canal 3 miles could take anything from an hour to most of the day depending on many factors that see you making little or no progress whilst the engine is still running. Litres per hour is a more meaningful metric, is far easier to measure and is more commonly used.

Agreed. A 100 mile out and back trip could use 100l out and 300l back.  The only sensible way to measure fuel consumption is in volume and time.

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10 hours ago, Crow said:

Hello all ,after removing a 15 hp Mercury  petrol  outboard and installing a 25 hp 3 pot vetus  , mated to a Enfield leg and a 13x8 or 9 prop in my little  25 ft springer. Would you think 3. kilometers  / litre.       Or about  2. 5    litre / hr  is  acceptable or a mile away from what it should be,thanks,Nick.

I'd say that's not far out, assuming you are talking about a straight run with no stopping on a narrow canal (is that possible?).  I've got recorded data for the last four years and I reckon I get about 10 mpg or about 3.5 kilometres/litre  when cruising on canals at a constant speed around 3-4mph.  That's with a 24 HP Bukh which is probably more efficient than your Vetus but a heavier boat.    

As others have said, litres per hour is a more meaningful figure on canals and I suspect if you take measurements over normal cruising with slowing down for moored boats,  locks, etc that figure of 2.5 l/hr will come down a lot.

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10mpg, 3.5km/l, 3-4mph, :)

I havent measured fuel consumption in any meaningful way since I got a narrowboat, but I remember always referring to gallons per hour when sailing, (motoring), offshore.

I even have a sense that gallons per hour may also be more meaningful than mpg in a car. e.g. on a long motorway run I get about 40mpg, (average speed may be about 40mph), but my normal day to day driving pattern of 3 miles to work and back, and several short trips during each day, produces about 20mpg, (average speed about 11mph).

There is a bit of guesswork in the car figures, so the long trip might be 35mpg, with average speed different. 

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I'd say your 2.5 litres per hour is WAY too high unless you are hacking along at 5 knots.

All the narrowboats I've ever had have used around 1 litre per hour. Even this 68ft boat I'm in now with the 3.75 litre Kelvin engine still uses 1 litre an hour on average.

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13 minutes ago, Richard10002 said:

10mpg, 3.5km/l, 3-4mph, :)

I havent measured fuel consumption in any meaningful way since I got a narrowboat, but I remember always referring to gallons per hour when sailing, (motoring), offshore.

I even have a sense that gallons per hour may also be more meaningful than mpg in a car. e.g. on a long motorway run I get about 40mpg, (average speed may be about 40mph), but my normal day to day driving pattern of 3 miles to work and back, and several short trips during each day, produces about 20mpg, (average speed about 11mph).

There is a bit of guesswork in the car figures, so the long trip might be 35mpg, with average speed different. 

Sorry to veer off topic a bit but when we acquired our current car last January I left the average mpg alone and haven't reset it at any time, it's currently reading 39.2 mpg which is very close to the manufacturers claimed overall average of 40.4.  Must admit I was expecting the actual to be a lot lower than the claimed.

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18 minutes ago, Mike the Boilerman said:

I'd say your 2.5 litres per hour is WAY too high unless you are hacking along at 5 knots.

All the narrowboats I've ever had have used around 1 litre per hour. Even this 68ft boat I'm in now with the 3.75 litre Kelvin engine still uses 1 litre an hour on average.

Bear in mind what sort of boat this is, and we don't know where he took his measurements or how fast he was travelling.

But, he says 3km per litre, which is about 8.5 mpg.

He doesn't say but I reckon he's travelling at around 4mph to get those figures - it's a 25 foot Springer with a V hull remember.  When I had a boat like that I could average 4mph easily.

So 8.5 miles is taking about 2 hours and he's used 4.55 litres that's about 2.3 litres an hour, not far from his 2.5 l/hr figure.  

He might have been on the river where those figures make even more sense.

 

 

 

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2.5 L / h is high unless you're going faster than most canal speeds. On our narrowboat we use less than 2 L / h (15 T displacement, 38 HP Beta) and most of our cruising is at about 7 km / h.

We're just back from our month share in a converted oil tanker on the mainland: that's 35 T with a DAF 575.  From 300 km and 150 locks with 85 h of engine running, cruising mostly at about 9 km/h, we averaged 2.4 L / h.

Martin/

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Years ago I did a straight run of 40 miles from Runcorn to Plank Lane in our 25' Waterbug.  Actual moving time was about ten hours and I'm pretty sure I used around 6 gallons of fuel.  That's around 2.7 litres per hour, albeit with a petrol outboard.  Crow's diesel should be a bit more efficient though his boat will be a bit heavier, which is why I maintain his figures are about right.

Most people would never bother to work out their constant cruising mpg or lpk as it's pretty much irrelevant on canals, but if we were hitting 4mph I reckon ours is about 1.8 litres per hour.  That's a lot better than Crow's but I reckon my engine/transmission is more efficient.

When we were coming back up the Avon last year I reckon it went up to 3 litres an hour.  So overall rivers and canals I would have thought 2 to 2.5 litres an hour is about right for a cruising speed around 4mph. 

But our overall average litres per hour consumption is about 0.7 obviously because the engine is at very low revs or tickover much of the time in normal canal crusing.       

  

 

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Just looked back through our last few years fuel useage and we have averaged 5.4mpg which looking at the engine hours run averages out at about 1 gallon per hour. But that doesn't tell the whole story either as we know that on the canal we use far less and on the coast we use far more.

We don't overly worry about it and just put fuel in when it needs it. 

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I've timed the km marker boards on the witham.  And it's taking 8 mins / km. I need to work out my throttle position to get a 5 mph position may be I was going to fast on my previous test.  What i did do was fill a liter tin and run it dry   , and started with empty fuel filter. I'm on witham now to wards Boston so it's a good testing place 

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1 hour ago, Crow said:

I've timed the km marker boards on the witham.  And it's taking 8 mins / km. I need to work out my throttle position to get a 5 mph position may be I was going to fast on my previous test.  What i did do was fill a liter tin and run it dry   , and started with empty fuel filter. I'm on witham now to wards Boston so it's a good testing place 

upstream or downstream?

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2 hours ago, Crow said:

I've timed the km marker boards on the witham.  And it's taking 8 mins / km. I need to work out my throttle position to get a 5 mph position may be I was going to fast on my previous test.  What i did do was fill a liter tin and run it dry   , and started with empty fuel filter. I'm on witham now to wards Boston so it's a good testing place 

If that's the case, if you read my previous posts I reckon your fuel consumption is pretty much what you would expect.   

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2 hours ago, Crow said:

I've timed the km marker boards on the witham.  And it's taking 8 mins / km. I need to work out my throttle position to get a 5 mph position may be I was going to fast on my previous test.  What i did do was fill a liter tin and run it dry   , and started with empty fuel filter. I'm on witham now to wards Boston so it's a good testing place 

You will use less fuel heading to Boston then you will coming back.

Not much flow on the Witham but it us enough to make a difference.

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On 10/08/2017 at 11:22, Mike the Boilerman said:

Friend of mine has a Sunseeker with twin turbocharged Caterpillar diesels.

90 litres an hour at full chat. Yes, NINETY LITRES AN HOUR he tells me.

Each engine!

If his engines start leaking diesel into the sump like mine does it will be impressive!

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