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MattJaneyHeinz

Barrus Shire 45 max revs

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Hi all

 

Anyone got an idea of maximum rpm for a Barrus Shire engine?

 

We had an, erm, interesting experience earlier this year when we locked down from Gloucester basin onto the Severn, which had a fair flow in it at the time. Things were fine up to Upper Parting, but when we joined the main channel we found that we were barely making headway at what I think of as normal cruising revs of 2000rpm. Some progress at 2400 rpm - but what would be the maximum? OH was all "more revs, more revs" and I was all "the engines Jim, they cannae take it".

 

Cheers

Matt

 

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9 minutes ago, TheBiscuits said:

Rated Output/Speed

 

Shire 39 29kW (39hp) at 2000rpm

Shire 43 32kW (43hp) at 2300rpm

Shire 49 36.5kW (49hp) at 3000rpm

 

18 minutes ago, MattJaneyHeinz said:

Some progress at 2400 rpm - but what would be the maximum?

 

 

Hopfully not a 39 or a 43 or there may some damage is it was sustained for very long.

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13 minutes ago, TheBiscuits said:

You don't specify which one you have

 

I really should read post titles!  You have a 45 and said so ...

 

Shire 45 33kW (45hp) at 2600rpm

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At that sort of power you ought to have plenty of oomph to make headway against the current. Sounds to me like the boat may be under-propped.

 

I have done the Severn above Gloucester with 18hp. Somewhat slow, but progress nevertheless.

Edited by David Mack

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Very few engines in narrowboat size will achieve their maximum rated r.p.m.. Provided the max. rpm adjustment hasn't been tampered with, it should be safe to open the throttle to rhe max. 

 

Quick Google reveals 3000 rpm max on Shire 50, and 2800 max on Shire 45.

 

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Why can't people have the correct prop? ie one which just (but only just) allows the engine to reach the maximum rated rpm in open water.

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Just now, Keeping Up said:

Why can't people have the correct prop? ie one which just (but only just) allows the engine to reach the maximum rated rpm in open water.

That sounds like the OP. 

 

Engine max power at 2600 rpm, they were running it at 2400 rpm with more throttle left but didn't want to push any harder.

 

Now they know they can if they ever need to, assuming their tachometer is correctly set up ...

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Propeller science can be complicated. I guess many, many narrowboats have got the wrong propeller, many more have got something quite serviceable but a horrible shaped boat and more than a few have not got the space under the counter to swing the right dia. prop. I reckon there must be a few that have bunged a bigger engine in to get a bit more shove but are still spinning a 12 x 9 prop that has been there for 25 years.

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There is also the issue of noise. As you go up the revs your chances of being able to hear anyone become slimmer.

 

Our engine will spin up to 3600 in neutral but only 2400 in gear. Clearly over propped but I'm happy tootling along at 1300 rpm which will give me 3mph or thereabouts.

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5 minutes ago, Cheshire cat said:

Our engine will spin up to 3600 in neutral but only 2400 in gear.

 

Is that on a canal or in deep open water?

Edited by TheBiscuits
Quoting for clarity!

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My 57ft.  boat has a Barrus Shire 45.  Max revs in gear is 2100 so it may over propped.

When it was built the then owner had the prop changed to a coarser one as he said it needed too many revs to go at normal speed.

Tick over is 800 rpm, Narrow/shallow canal I use about 1200 to 1300 rpm and 1400 on the deeper and wider canals.

I have been flat out on the Thames going upstream on a wide straight bit above Reading. After about a minute I had three bow waves and was putting up quite a wash at the bank so I slowed down.

I don't know how fast we were going, but I would guess about 7 or 8 knots. (Naughty)

The Barrus manual says something like "Run the engine at full speed under load for 15 minutes every 25 hours to avoid build up of carbon"! Where can I do this?

It's a bit like my Volvo car. That needs a good thrash to clean the soot filter every once in a while.

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Brill, thanks for the replies all. Looks like we had a bit spare, which we can use next time in an emergency. The current was very strong that day - never had a problem any other time on the Severn. And running at full speed under load is recommended - 15 mins every 50 hours, under load. Manual says do it moored up (securely!) if this would break the speed limit.

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23 hours ago, TheBiscuits said:

 

Is that on a canal or in deep open water?

I have tried it on the canal and also on the Trent between Sawley and the Erewash. I don't recall any noticeable difference in maximum achievable revs although the engine seemed smoother in the deeper water.

 

I was toying with the idea of buying a larger blade  until I realised the engine couldn't even spin the one we already have as well as I expected.

15 minutes ago, MattJaneyHeinz said:

And running at full speed under load is recommended - 15 mins every 50 hours, under load. Manual says do it moored up (securely!) if this would break the speed limit.

I think you might find that C&RT will frown upon this.

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On 18/10/2020 at 21:10, Keeping Up said:

Why can't people have the correct prop? ie one which just (but only just) allows the engine to reach the maximum rated rpm in open water.

One reason could be that this would not allow maximum power to be reached when in less-than-open-water or when towing. 

 

The revs at which max power is delivered is usually below the safe limit.  So if you did gear/prop your engine to deliver max power in other circumstances, when in open water no great harm would arise as long as you did not allow the revs to rise above the maximum permitted.

 

Do tugs and the like have a choice of ratios and variable pitch propellers?

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Pretty sure mine can deliver full power in less-than-open waters, not that it's generally needed in those circumstances, including when towing or doing an Emergency Stop. I have never towed anything heavy in wide open waters so can't answer for that situation.

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