barrysnowball Posted October 24, 2014 Report Share Posted October 24, 2014 If I had 2 narrowboats which in all other respects were the same, but one had an old low revving thumper, and the other had a modern high revving growler, which would have the better fuel economy? Link to comment Share on other sites More sharing options...
RLWP Posted October 24, 2014 Report Share Posted October 24, 2014 Neither They would both come out at about 1 litre an hour. Practically all narrowboats do, no matter what engine Richard Link to comment Share on other sites More sharing options...
BenC Posted October 24, 2014 Report Share Posted October 24, 2014 Which would you prefer? Which would you prefer? Link to comment Share on other sites More sharing options...
nicknorman Posted October 24, 2014 Report Share Posted October 24, 2014 (edited) Neither They would both come out at about 1 litre an hour. Practically all narrowboats do, no matter what engine Richard Ours routinely averages 1.6l/hr at modest speed. (Beta 43 with 3 alternators) So I think that slow revving (less friction) under-alternatored engines are quite a bit more economical. Also, a smaller engine working reasonably hard is more economical than a larger engine working less hard but producing the same power Edited October 24, 2014 by nicknorman Link to comment Share on other sites More sharing options...
Southern Star Posted October 24, 2014 Report Share Posted October 24, 2014 Neither They would both come out at about 1 litre an hour. Practically all narrowboats do, no matter what engine Richard Mine has a BMC 1.5 and although I've only put 70 hours on it since I bought it, dipping the tank with the gradiated dipstick suggests that it has used almost exactly 70 litres of diesel. Link to comment Share on other sites More sharing options...
Black Country Lee Posted October 24, 2014 Report Share Posted October 24, 2014 (edited) You want a proper engine... (Sorry for the image size, borrowed from a fave website of mine lol) Lee. E.T.A. - You don't want the gearbox though, semi-auto Voith, utter utter pants! Edited October 24, 2014 by Black Country Lee Link to comment Share on other sites More sharing options...
Dalslandia Posted October 24, 2014 Report Share Posted October 24, 2014 a modern common rail engine might be 10% better in diesel drinking, but a good or bad propeller might be a difference of 20% or more. Link to comment Share on other sites More sharing options...
by'eck Posted October 24, 2014 Report Share Posted October 24, 2014 Ours routinely averages 1.6l/hr at modest speed. (Beta 43 with 3 alternators) So I think that slow revving (less friction) under-alternatored engines are quite a bit more economical. Also, a smaller engine working reasonably hard is more economical than a larger engine working less hard but producing the same power But what of slow revving over alternatored engines - higher fuel consumption but electrical bliss Link to comment Share on other sites More sharing options...
ditchcrawler Posted October 24, 2014 Report Share Posted October 24, 2014 You want a proper engine... (Sorry for the image size, borrowed from a fave website of mine lol) Lee. E.T.A. - You don't want the gearbox though, semi-auto Voith, utter utter pants! I have seen several boats fitted with old Gardner bus engines Link to comment Share on other sites More sharing options...
matty40s Posted October 24, 2014 Report Share Posted October 24, 2014 You want a proper engine... yebbut, yebbut, yebbut, its not in a boat. fishing vessel or thames tugboat yes., absolutely. Link to comment Share on other sites More sharing options...
nicknorman Posted October 24, 2014 Report Share Posted October 24, 2014 But what of slow revving over alternatored engines - higher fuel consumption but electrical bliss No - the alternators go too slowly to do anything useful! Link to comment Share on other sites More sharing options...
by'eck Posted October 24, 2014 Report Share Posted October 24, 2014 No - the alternators go too slowly to do anything useful! Great so that restores the economy Link to comment Share on other sites More sharing options...
by'eck Posted October 24, 2014 Report Share Posted October 24, 2014 I have seen several boats fitted with old Gardner bus engines 6LXB = Gardner 180 - hmm! yebbut, yebbut, yebbut, its not in a boat. fishing vessel or thames tugboat yes., absolutely. Link to comment Share on other sites More sharing options...
Black Country Lee Posted October 24, 2014 Report Share Posted October 24, 2014 You'd be OK on the Erie Canal though Link to comment Share on other sites More sharing options...
Timleech Posted October 25, 2014 Report Share Posted October 25, 2014 A bigger prop is to some degree more efficient than a smaller, faster turning one - but then a boat able to turn a bigger prop may need to have a greater draught, which will create more drag (or need to travel more slowly) on shallow waterways, so there's an element of 'swings and roundabouts' on that one. Tim Link to comment Share on other sites More sharing options...
barrysnowball Posted October 25, 2014 Author Report Share Posted October 25, 2014 Thanks for all the useful comments. In answer to "Which do I want", it is most certainly on old thumper. I love working on engines, and they were so beautifully engineered. I'm glad that fuel costs is no longer a deciding factor. All I have to do now is find the right boat. The searching will be as pleasant as the buying. Thanks again for all your replies. Barry. Link to comment Share on other sites More sharing options...
Dalslandia Posted October 26, 2014 Report Share Posted October 26, 2014 (edited) A bigger prop is to some degree more efficient than a smaller, faster turning one - but then a boat able to turn a bigger prop may need to have a greater draught, which will create more drag (or need to travel more slowly) on shallow waterways, so there's an element of 'swings and roundabouts' on that one. Tim That's correct, but using the largest possible within its limitation of the boat and practicality, and pick a gear ratio to give an optimal propeller size/rpm to suit. and use a efficient designed propeller. but there is also different efficient designs with the same diameter/pitch and different layout of the swim that change the inflow to the propeller if a modern engine is 10 % more efficient then an older, but use a 20% less efficient propeller, the result is that the older one seems to be more efficient. Edited October 26, 2014 by Dalslandia Link to comment Share on other sites More sharing options...
Bee Posted October 26, 2014 Report Share Posted October 26, 2014 Honestly, at first glance at the pic. I thought someone had fitted that into the boot of a trabant or something, its a bus innit, seriously though, there will not be a vast difference, to shift, say 20 tons at 4 mph requires x calories / kilowatts of diesel burnt and so long as rhe engines are not extreme examples the fuel used will be similar., (I failed o level physics by the way so please don't shout) Link to comment Share on other sites More sharing options...
Alan de Enfield Posted October 26, 2014 Report Share Posted October 26, 2014 45 foot NB, Lister LPWS4, 3:1 Hydraulic gear box, 1800 rpm gives 3-4 mph = 2.1 litres per hour Link to comment Share on other sites More sharing options...
Dalslandia Posted October 26, 2014 Report Share Posted October 26, 2014 (edited) 45 foot NB, Lister LPWS4, 3:1 Hydraulic gear box, 1800 rpm gives 3-4 mph = 2.1 litres per hour make sense. saw someone doing 2.8 mph average, and using 1 liter or so. 3-4 mph is 3.5? 3,5/2,8=1,25 ^3 = 1,95 liter/h most diesel engines use the same amount of fuel per HP, it just need some amount of fuel to run the speed of the boat have big influence on power and fuel needed V ^3 (or^2.8) Edited October 26, 2014 by Dalslandia Link to comment Share on other sites More sharing options...
Peter-Bullfinch Posted October 26, 2014 Report Share Posted October 26, 2014 1977 Sabb 22hp in a 57ft trad with a Borg Warner Velvet Drive gives 1.05 l/h. Canals or rivers seem to make little difference. Link to comment Share on other sites More sharing options...
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