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Wrinkley

2LW revs and is it possible to up them?

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My 2lw runs as sweet as a nut. Start easily and stops the waft of smoke after 10 -15 mins from cold. It has a 22 x 22 prop on a 2:1 gearbox. Just came up the Thames flat out at 860 rpm which was fine but nothing in reserve. No smoke from exhaust, no increase in water or oil temperature so not over loading engine. Last year on the Trent could of done with a bit more power/revs as we came to a crawl going towards Keadby lock against the in coming tide. Apart from fitting another prop or adjusting the one on the boat it there an adjustment that can be made to help? Don't want to fit another cylinder.

 

Graham

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What does the rating plate say?

One option is to take the whole pump/governor/cambox assembly to a fuel pump specialist who still understands these things and has the kit to do it, and get them to set it for a recognised marine horsepower/rpm (eg 1300 rpm). If that makes no real difference, your prop is too big.

 

Tim

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My 50ft Heywood shell with a JP2M and a 2:1 reduction was also fitted with a 22 x 22 prop and was terrible on rivers. I then fitted a compensated crowthers prop and it's much better now....was fine on tidal Trent and Ouse last year.....wasn't cheap at £850 five years ago but well worth it. Possibly not the answer you were looking for I'm afraid!

 

Cheers

 

Gareth

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Thanks for the replies.Yes, the Walsh's plate on the side of pump says 29 bhp and 1300rpm. I assume that the pump was set to this rating? Is it the pump that controls the revs then and not the governor?

 

Whilst I would like more revs I would not describe the performance as terrible, just like a bit more. Need to Google compensated crowthers prop to see what one of these is.

 

Out of gear and well warmed up it revs to over 1200 rpm

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What does the rating plate say?

One option is to take the whole pump/governor/cambox assembly to a fuel pump specialist who still understands these things and has the kit to do it, and get them to set it for a recognised marine horsepower/rpm (eg 1300 rpm). If that makes no real difference, your prop is too big.

 

Tim

I have never understood why the maximum marine horsepower/rpm rating is less than the maximum traction ratings. Maybe the 'marine rating' is the 'continuous rating' and no road or rail vehicle was expected to run continuously at maximum power/rpm? I see no reason that a competent operator should not cruise within the 'marine rpm limit' and have extra power available if needed.

 

I also found a, rare, occasion when increasing the power to the traction limit for a few minutes would have been convenient, e.g. trying to get through Newbury Town Bridge shortly after the floods subsided (<9", one brick, per second) an increase in power for two minutes would have changed my boat from over-propped to ideal or under-propped. Unlike my over-propped canal boat, a true 'marine' application would be expected to have the correct ratios to reach maximum power/rpm in open water.

 

Alan

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Interesting as with a 22 x 22 my JP was definitely underpropped. Are the torque figures vastly different for the two engines? We now have a decent cruising speed on deeper water that was lacking before.

 

Cheers

 

Gareth

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Interesting as with a 22 x 22 my JP was definitely underpropped. Are the torque figures vastly different for the two engines? We now have a decent cruising speed on deeper water that was lacking before.

 

Cheers

 

Gareth

 

A prop which is right for 21hp@ 1200 rpm should only need about 27hp to turn it at 1300 rpm, but that's not a huge margin below the 29hp of the Gardner. My guess is that it's a slightly bigger than average 22 x 22 that the OP has.

One little experiment I'd be inclined to try is to set the speed control for a higher speed than the engine will manage, and then press up the cold start button. There will certainly be some black smoke initially, but does the engine then settle down to a higher speed with no smoke? Obviously if there is constant black smoke, end the experiment and conclude that it is over-propped.

 

Tim

Edited by Timleech

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Interesting as with a 22 x 22 my JP was definitely underpropped. Are the torque figures vastly different for the two engines? We now have a decent cruising speed on deeper water that was lacking before.

 

Cheers

 

Gareth

 

Confirms my experience with 24 x 22 Crowther prop on JP2M although don't know the BAR. Revs easily to 900 rpm plus on deepish rivers.

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Don't forget that the sizing of the prop is also down to the waterline length and draught of the hull,clearances from the prop shaft to the uxter plate and the design speed of the vessel. All of these things including the horse power and torque curve of the engine are factors to be calculated when sizing the prop. Experiences with a JP are unlikely to be similar to a 2LW and can't be compared like for like.

 

Add to this the different performance characteristics of Crowther and Axiom props (and the other types) married to the hopelessly inadequate hull design of most narrowboats and its easy to see why some boats are horrible on rivers and better on canals and vice versa. Or just awful full stop.

 

One thing I am sure of is that some of the boat builders don't really have a clue. The one in the workshop will always be the right size! clapping.gif The careful consideration of all the factors and, once this is calculated, consultation with the prop manufacturers is the best way forward and ,sadly, is seldom done.

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Don't forget that the sizing of the prop is also down to the waterline length and draught of the hull,clearances from the prop shaft to the uxter plate and the design speed of the vessel. All of these things including the horse power and torque curve of the engine are factors to be calculated when sizing the prop. Experiences with a JP are unlikely to be similar to a 2LW and can't be compared like for like.

 

Add to this the different performance characteristics of Crowther and Axiom props (and the other types) married to the hopelessly inadequate hull design of most narrowboats and its easy to see why some boats are horrible on rivers and better on canals and vice versa. Or just awful full stop.

 

One thing I am sure of is that some of the boat builders don't really have a clue. The one in the workshop will always be the right size! :clapping: The careful consideration of all the factors and, once this is calculated, consultation with the prop manufacturers is the best way forward and ,sadly, is seldom done.

Fair enough.....like I always say everyday is a school day!.....I have less than ideal clearance to the uxter plate...ie bu**er all! But having more means less diameter....like most things on a boat it's a compromise! I would still like more speed on deep water but think that's not going to happen so I'll live with it.

 

Cheers

 

Gareth

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If the engine will rev to 1200 RPM off load, and only 680 RPM on load, then al it means is that the load is too great for the way the engine fuelling is set to give full revs. It's also possible that the engine is, in fact, giving its full rated power at 680 RPM. The fact that there is no smoke means that the maximum fuelling is set to give full combustion of all injected fuel, and that the engine is in good general condition. If you were getting black smoke, the fuelling would have been set too high for the fuel to burn completely.

 

It may be that the fuel feed from the injector pump has been set lower than normal in order to improve fuel economy, and that it could be increased, but that would need to be done by a qualified engineer to ensure that the engine wasn't damaged in the process.

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Odd. Sounds desperately under-propped to me.

 

An under-propped engine would tend to reach max governed revs, as the prop wouldn't provide enough load to limit this. The OP is experiencing the exact opposite, although it appears the governor/injection pump setup is doing a good job of preventing black smoking.

 

If the engine will rev to 1200 RPM off load, and only 680 RPM on load, then al it means is that the load is too great for the way the engine fuelling is set to give full revs. It's also possible that the engine is, in fact, giving its full rated power at 680 RPM. The fact that there is no smoke means that the maximum fuelling is set to give full combustion of all injected fuel, and that the engine is in good general condition. If you were getting black smoke, the fuelling would have been set too high for the fuel to burn completely.

 

It may be that the fuel feed from the injector pump has been set lower than normal in order to improve fuel economy, and that it could be increased, but that would need to be done by a qualified engineer to ensure that the engine wasn't damaged in the process.

 

By definition it will be impossible for the engine to provide its full rated power at less than its rated rpm, even at 860 rpm wink.png

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An under-propped engine would tend to reach max governed revs, as the prop wouldn't provide enough load to limit this. The OP is experiencing the exact opposite, although it appears the governor/injection pump setup is doing a good job of preventing black smoking.

 

 

By definition it will be impossible for the engine to provide its full rated power at less than its rated rpm, even at 860 rpm wink.png

 

I said it because my 21hp Kelvin is turning a 21 x 19 blade on a 1:1 transmission. This is a little over-propped, so the 29hp engine in the OP turning a 22 x 22 blade appears to me quite under-propped given it has a 2:1 reduction gear.

 

My implication which I failed to spell out, was this is why the boat feels underpowered.

 

The engine's failure to rev to 1,300rpm stated on the engine data plate would, I suspect, be a separate problem.

 

 

MtB

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I said it because my 21hp Kelvin is turning a 21 x 19 blade on a 1:1 transmission. This is a little over-propped, so the 29hp engine in the OP turning a 22 x 22 blade appears to me quite under-propped given it has a 2:1 reduction gear.

 

My implication which I failed to spell out, was this is why the boat feels underpowered.

 

The engine's failure to rev to 1,300rpm stated on the engine data plate would, I suspect, be a separate problem.

 

 

MtB

 

I see your thinking but you are trying to compare a 4 litre 750 rpm single cylinder engine with direct drive, to a 2.8 litre twin 1300 rpm one with 2:1 reduction. Too many variables to compare like for like surely. Note also OP's engine revs freely when off load.

 

My first thought as probably yours, was that a 22 x 22 prop didn't seem too large, compared say with that on my JP. But as steamraiser says you can't even compare these similar config, same reduction engines.

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I'll try the cold start button trick tomorrow and report back.

 

Thanks to all for help. I know just enough about injection pumps to leave them well alone. But that does not stop me wondering what sort of adjustmenst are in there? When the pump was repaired two years ago the guy set it up with a dial gauge and adjusted what looked like upside down tappits. These were set to measurements (each slightly different) sent with the pump from the man that did the repair back at base. Is this the adjustment or are there others? Don't concern yourselves, I will not touch it.

 

Graham

ps Any books or internet sites that might help with my curiosity?

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Graham

ps Any books or internet sites that might help with my curiosity?

Google CAV BPF injection pump manual and you will find a copy.smile.png

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I'll hazard a guess that the maximum fuel stop on the pump rack is not quite correctly set. My little test of pressing up the cold start button when under load will give some indication as to whether it is or not.

 

Tim

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Both fuel filters changed 140 hrs ago.

I got excited when I said I would get the engine warm and flat out today The cold start test will probably have to wait a couple of weeks as we are now on the R Wey. They may not take kindly to me giving it a gob full and some (its very pleasant here). Two weeks time we should be back on the Thames and have a blast. I will report back then.

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So today returned to Thames. Warm engine, clear river, flat out and then pressed the cold start button. As suggested "There will certainly be some black smoke initially, but does the engine then settle down to a higher speed with no smoke?" Yes it did! I saw some smoke and the revs increased. To what I don't know as I can not see the taco from that side of engine. I only kept the button in for approx 30 sec as co-pilot not happy hanging on to the tiller at speed. What does this mean?

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Nothing beyond the fact that ,while you held the cold start button in, it allowed the rack to be fully open beyond the normal top speed setting. You really need to set up the pump and governor correctly. It's a bit of a pain to do and Martyn1 has already explained it in some detail on another Gardner thread within the last week. If you follow those instructions and set it up correctly it may help to cure your problem. Won't do a thing if your boat turns out to be over propped though.

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