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DM2 vs DM3


barmyfluid

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...on a 60 foot boat, river duties, quite a lot of liveaboard charging at moorings over winter....

 

Overkill on motive power, underworking for charging/heating asking for trouble?

Future issues with certain spares - have read that they're not building DM3's any more?

 

Other than just the 'phwoar' factor of the magic number, any mechanical maintenance pro's and cons of DM2 vs DM3?

 

I've got my eye on a DM3 trad and it just seems such a lot of engine, and I hear of far more DM2 installations....

 

bx

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The RNs are not the most powerful of the vintage engines so if you plan a lot of river cruising, and especially if you do rivers when they are flowing a bit, then the 3 would be the better engine, but on the other hand, in my opinion, a two cylinder engine always sounds much nicer.....and the two would be perfectly adequate for canals and all normal river stuff.

 

................Dave

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Looking at the absolutely eye-watering cost of RN spares, I think I would prefer an engine that had 2/3 the number of any bits that are on a "per cylinder" basis.

 

Clearly the 2-pot used to be capable of adequately propelling 2 fully loaded 72 foot narrow boats, but probably not that often on rivers with significant currents, and certainly not also used as a large electrical generator.

Edited by alan_fincher
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I've only ever spoken at length with one RN owner, and he was bitterly disappointed with his DM2 saying it was grossly underpowered for his boat. 

 

I offered him fifty quid for it but for some reason he seemed to want to keep it rather than get a better engine. 

 

The fool....

 

 

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Talk to Dave Bixter at RN before you do anything - DM3's are VERY difficult to maintain many spares are simply not available any more - DM2 much better all round but I sold my last one due to lack of power and rapidly increasing cost of spares and related labour - if you want a "posh" engine for rivers in particular 2LW or 3LW any day for me 

 

I wrote this last night but it didn't post for some reason

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11 minutes ago, Halsey said:

Talk to Dave Bixter at RN before you do anything - DM3's are VERY difficult to maintain many spares are simply not available any more

That surprises me - I would have thought that the DM2 and the DM3 had many parts in common.

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20 minutes ago, Athy said:

That surprises me - I would have thought that the DM2 and the DM3 had many parts in common.

They do but the bits that aren't in common aren't there - cranks in particular but its the maintenance costs that seem to have gone silly - Dave is a mate and he put me off buying a 3 on a nice boat I found a few years back

 

Whatever it is though I would always go for 2cyls  if you want that "classic" feel - 3's don't do it for me at all, far too smooth.

Edited by Halsey
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Thanks all, and for the PM's too.

 

The boat is a rather nice RW Davis that ticks a lot of boxes, shame about the engine. It could of course outlast me, have little trouble and how often does a crankshaft snap.....but if it didn't.... *shudders*. 

 

bx

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2 minutes ago, barmyfluid said:

Thanks all, and for the PM's too.

 

The boat is a rather nice RW Davis that ticks a lot of boxes, shame about the engine. It could of course outlast me, have little trouble and how often does a crankshaft snap.....but if it didn't.... *shudders*. 

 

bx

 

 

If it snaps never mind shuddering, just buy a proper engine like a Kelvin K2....

 

 

If you can afford an RW Davis boat you can surely afford a replacement engine :giggles:

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8 minutes ago, Mike the Boilerman said:

 

If you can afford an RW Davis boat you can surely afford a replacement engin:giggles:

  I doubt I could afford a RN badge after the boat, or fuel. that's why I'm so wary of the engine! I could polish the brass with my own tears I suppose.......

 

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2 minutes ago, barmyfluid said:

  I doubt I could afford a RN badge after the boat, or fuel. that's why I'm so wary of the engine! I could polish the brass with my own tears I suppose.......

 

 

 

Do what I do with my Kelvins. Polish it with £50 notes.....

Comes up a treat!!

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10 minutes ago, barmyfluid said:

  I doubt I could afford a RN badge after the boat, or fuel. that's why I'm so wary of the engine! I could polish the brass with my own tears I suppose.......

 

If you want the whole truth talk to Dave Bixter who owns RN and Granthams Bridge etc 07812 039110 - totally straight guy been my "go to" for 20+ years - you might decide its still worth a go esp if he knows the engine - also Richard Milligan of this parish (RNs a specialty) as he might know it.

 

Don't forget the vendor will know DM3 issues so try a VERY low offer to see if you can build in a cushion now 

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10 minutes ago, Halsey said:

Don't forget the vendor will know DM3 issues so try a VERY low offer to see if you can build in a cushion now 

 

^^^This^^^

 

The vendor will be very aware of the DM3 issues and this may well be the reason for selling the boat. 

 

 

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14 hours ago, Mike the Boilerman said:

I've only ever spoken at length with one RN owner, and he was bitterly disappointed with his DM2 saying it was grossly underpowered for his boat. 

 

I offered him fifty quid for it but for some reason he seemed to want to keep it rather than get a better engine. 

 

The fool....

 

 

Back in the distant past I had delivered a load of interlocking steel piles on the Nene  Ken Roseblade  had some pairs on a timber run Peterborough to Nottingham ? the Nene had a bit of a flood on & one of his motors IIRC DM 2 powered ?didn't have sufficient "umph " to force its way through the bride hole against the flow hooked up "Lily" on a snubber & pulled the pair through the bridge hole One pot Semi diesel power to the rescue no Idea if it was general lack of power or an engine problem  but the "Seffle"s 25HP direct drive box seemed to cope no problem with a "few"gallons of water in the bilge to get the back end down

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1 minute ago, Halsey said:

Don't forget the vendor will know DM3 issues so try a VERY low offer to see if you can build in a cushion now 

I'd have to go in low regardless, it's right at the top of my budget, but I don't think it's the right engine for me. Lovely shell though.

 

Browsing the Gardner spares catalog, much more reasonable....

 

bx

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1 hour ago, Halsey said:

If you want the whole truth talk to Dave Bixter who owns RN and Granthams Bridge etc 07812 039110 - totally straight guy been my "go to" for 20+ years - you might decide its still worth a go esp if he knows the engine - also Richard Milligan of this parish (RNs a specialty) as he might know it.

 

Don't forget the vendor will know DM3 issues so try a VERY low offer to see if you can build in a cushion now 

Does one make very low offers on a Davis Northwich Trader?   or even slightly low offers?   and can you make a low offer on the grounds of a hypothetical engine failure in the future?.  Its made of mild steel so maybe a low offer because it will need replating at some time in the future ?

 

..............Dave

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37 minutes ago, dmr said:

Does one make very low offers on a Davis Northwich Trader?   or even slightly low offers?   and can you make a low offer on the grounds of a hypothetical engine failure in the future?.  Its made of mild steel so maybe a low offer because it will need replating at some time in the future ?

 

..............Dave

Its not a Northwich trader but the far less desirable (but still good) Heritage Class - and yes I would offer hard on anything with a DM3 in it - I did once and it was turned down flat and 12 months later it sold for less than I had offered - you can always go up or walk away.

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2 hours ago, barmyfluid said:

Thanks all, and for the PM's too.

 

The boat is a rather nice RW Davis that ticks a lot of boxes, shame about the engine. It could of course outlast me, have little trouble and how often does a crankshaft snap.....but if it didn't.... *shudders*. 

 

bx

Generally speaking two cylinder engines suffer from snapped crankshafts, the three cylinder versions tend to have an extra central support. 

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12 minutes ago, Halsey said:

Its not a Northwich trader but the far less desirable (but still good) Heritage Class - and yes I would offer hard on anything with a DM3 in it - I did once and it was turned down flat and 12 months later it sold for less than I had offered - you can always go up or walk away.

It's got 12/6/4/4 steelwork, and I'm more enamored of Davis' maritime engineering credentials than traditional re-creation stylyings, seems like a solid and practical boat worth spending a bit more for. If it had a Bukh DV36 in an engine room....*drool*

 

The DM3 does sound like a bit of an albatross in it and they must know that - it's *someones* dreamboat, but how long before they come along?

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1 hour ago, dmr said:

Does one make very low offers on a Davis Northwich Trader?   or even slightly low offers?   and can you make a low offer on the grounds of a hypothetical engine failure in the future?.  Its made of mild steel so maybe a low offer because it will need replating at some time in the future ?

 

..............Dave

If the boat is Dora, then I don't think it's a Northwich Trader.

In fact it seems to avoid some of the excesses of a Northwich Trader, such as vast numbers of faked rivets on the whole superstructure, and in my personal view is a very much nicer boat as a result!

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6 hours ago, BWM said:

Generally speaking two cylinder engines suffer from snapped crankshafts, the three cylinder versions tend to have an extra central support. 

 

Surely a three cyl would have to have two extra central supports (by which I imagine you mean main bearings), or none, given the location of cylinder No 2 :D

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On 26/10/2018 at 21:53, alan_fincher said:

Clearly the 2-pot used to be capable of adequately propelling 2 fully loaded 72 foot narrow boats, but probably not that often on rivers with significant currents, and certainly not also used as a large electrical generator.

 

'On completion of their apprenticeships, Frederick Russell and William Newbery setup their own business, the Russell Newbery Company. In 1909 they opened a works at Altrincham, now a suburb of Manchester, it was then a small provincial Cheshire town. Frederick's father underwrote the firm to the tune of £11,000, equivalent to over one million pounds today. The company was established to produce lighting sets and generators for country houses and estates, a sizeable market before the advent of the national electricity grid.'

 

https://www.rnregister.org.uk/history_1.html

 

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1 hour ago, rupertbear said:

 

'On completion of their apprenticeships, Frederick Russell and William Newbery setup their own business, the Russell Newbery Company. In 1909 they opened a works at Altrincham, now a suburb of Manchester, it was then a small provincial Cheshire town. Frederick's father underwrote the firm to the tune of £11,000, equivalent to over one million pounds today. The company was established to produce lighting sets and generators for country houses and estates, a sizeable market before the advent of the national electricity grid.'

 

https://www.rnregister.org.uk/history_1.html

 

 

Gosh, I imagined the National Grid had existed for as long as electricity!

 

So this means there could have been conversations in country houses along the lines of: Mrs: "would you turn on the light please darling?"... Mr: "yes but hang on a minute, I can't find the blasted starting handle!"

 

 

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