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Diesel engines (again)


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#1 Chrisc

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Posted 14 February 2018 - 12:48 PM

Thanks to my research and also in no small way to the appreciated advice received from forum members on my previous engine post, we are starting to get quite comfortable with the idea of owning a vessel propelled exclusively by the dreaded infernal combustion engine.
We are even accepting of an engine with higher hours, especially when I consider that I confidently expect my heart to deliver around 2.5 billion trouble free contractions, so wanting to make 5- 8000 hours on an engine is not so much.
It's still a bit confusing, though.
For a variety of reasons we would like to limit our intended canal boat to 80 - 100 HP. The boats that we have looked at (online) within this HP rating seem equally split between 4 and 6 cylinder units. One would think it cheaper to maintain a 4cyl engine, so what would be the benefits of a 6cyl, and would they be cost effective?
And, we think we have finally solved the riddle of why so many European boats get re-engined. We have quotes from a large well regarded supplier in the Netherlands to re-engine with a re-manufactured 80hp diesel, any of the main brands, complete and with a new engine guarantee of around €4700 - €5200. Seems pretty reasonable and well worth it to me.
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#2 harrytom

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Posted 14 February 2018 - 03:43 PM

Probably a silly question,but are there canal boats with petrol engines??why I am asking is it seems petrol is quite happy idling over or running at reduced revs compared to diesel,most small diesils need to run at 3/4 throttle so probably answering my own question now,6 cylinder diesils  may not wear as much as 4?


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#3 Chrisc

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Posted 14 February 2018 - 04:19 PM

Have not seen any petrol powered canal boats.
My opinion based on not really knowing what I'm talking about is that for every rotation of the crankshaft 4 pistons travel up and down, and 6 pistons on a 6 cylinder engine. Since a 6 cylinder engine rotation infers that the pistons are more evenly spread over the crankshaft rotation because there's more of them ( sorry, I'm not explaining this theory very well) but the end result may be that a 6 cyl is a smoother running engine. If that's the only benefit then the extra costs involved in servicing 6 injectors, fuel pump etc over a 4 cyl does not really seem worth it.
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#4 Bad Kitty

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Posted 14 February 2018 - 04:21 PM

LRSF_0669-CrashTestExplosion11-LMc.jpg

 

Petrol in boats, Awesome!


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#5 Bad Kitty

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Posted 14 February 2018 - 04:23 PM

Given how rarely injectors need work, & that a 4 cylinder diesel still needs an injector pump anyway, albeit slightly simpler, I wouldn't have thought the running costs much different?

Could be wrong though,


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#6 Chrisc

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Posted 14 February 2018 - 04:37 PM

Given how rarely injectors need work, & that a 4 cylinder diesel still needs an injector pump anyway, albeit slightly simpler, I wouldn't have thought the running costs much different?
Could be wrong though,

4 extra valves, more fuel lines, more bushes, bearings and other wear surfaces, presumably a longer engine, bigger oil capacity...
I'm not against 6 cylinders, as a proponent of the KISS system, I would just like to know what benefits (or otherwise) there are in choosing an 80hp 6 cyl over an 80hp 4 cyl.
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#7 Steve Pope

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Posted 14 February 2018 - 04:43 PM

Running costs will be similar, given that you run either engine near the peak torque setting rather than rely on revs.. more revs = more fuel. Maintenance will be negligeable ( apart from the usual filters, oil etc.) if the motor you start with is in good nick. I doubt that you would ever have to do the injectors. My preference would be 6 cyl, better balance, less vibe = happier engine mounts etc. As I have already said normally aspirated is less prone to fuel issues against common rail engines. Have a look at Lancing marine in the UK, they do a lot of engine stuff, you can get an idea and compare prices on line.


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#8 wheels

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Posted 14 February 2018 - 04:58 PM

Very simply, the more cylinders, the more CC's and thus the more power. So usually a 4cyl will have less power than a 6cyl. More power means more fuel. Diesels, if the load is correctly balanced to the engine size, use a pretty good rule of thumb measure of Fuel /Hp/RPM.
The weight difference is not usually a biggy in a Displacement Hull. Longevity is where the big difference comes in. A 6 cyl will run far higher hrs than a 4. Simply because they tend to rev much slower. Yes they are much smoother running with a lot more torque, due to 2 extra pistons firing within the rotation sequence. This also results in less heat per pot and thus less combustion wear, so hence the higher hrs before rebuild.
A 6 will usually have a much larger Sump capacity and often have twin oil filters, or a single much larger one than the 4. Also a much larger Starter, so larger Engine start Battery. A larger heat output, so larger Heat exchanger. The engine is much heavier, so removal needs heavier lifting equipment. Some smaller 4's can be manhandled in and out. You won't do that with a 6.


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#9 Chrisc

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Posted 14 February 2018 - 07:33 PM

Good stuff. Thank you.
Dutch built canal boats of around 10-12 m are all very similar, like modern cars. Their dimensions are governed by the environment they operate in and in providing the most efficient and comfortable use of internal space, means that they all end up looking the same.
So the only thing to choose between then is presentation, what goodies they come with and of course, the engine.
So, from your replies, if the engine is low in hours we will accept a 4 or 6 cyl with a bias perhaps towards the 6. If it's an engine with higher hours then a definite preference for the 6.
Thanks for your input - now the wife would like me to pack my bags and go look at a couple of boats she's selected. -6° in Rotterdam last time I looked.
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#10 John B

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Posted 14 February 2018 - 08:57 PM

An 80 horse 4 cyl is probably turbocharged , which I have myself but would prefer not. It pushes a 45 ft yacht at about 6.5 to 7 at 2.7 lph. Mostly running low at say 2200 or so and using about 50 of the available hp. Euro canals speed limits are about that? British canals were much lower... I forget but seem to recall around 3 or 4 mph.Anyway ... 80 or 100 hp seems a lot for a canal.
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