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Old 08-20-2019, 05:33 PM   #1
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JD engines ómechanical vs. electronic

Thought experiment for those who know their Diesel engines: if you had a choice between to sets if engines in a boat, both John Deere 6068T, one one set was the old technology mechanical fuel injection, and the other was the newer common rail electronic injection, which would you choose and why? Also, what price difference, if any should someone expect to pay for electronic common rail engines over mechanical engines if the same type, all else being equal? Assume both sets have been well maintained and have 1500 hours.

Thanks.
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Old 08-20-2019, 05:57 PM   #2
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Well, it is a tradeoff.

Common rail engines are smoother, smoke less, are slightly more efficient, and are better for the environment. OTOH they are subject to electronic failures.

If I were selecting an engine for a boat that was going to cross oceans then I definitely would choose mechanical. Otherwise it is a toss up. I certainly wouldn't pay more for an electronic engine.

David
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Old 08-20-2019, 06:26 PM   #3
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If I was running a 1000 hrs a year and not crossing oceans, I would pick the electronic engine, better fuel consumption.
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Old 08-20-2019, 06:40 PM   #4
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Watching this with some interest.

I have the Lugger(JD) 6068Ts (174hp).
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Old 08-20-2019, 08:51 PM   #5
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You inserted an interesting qualifier.
If I were going to cross oceans with a single, I would probably want the mechanical engine. For coastal cruising in most of North America, a single electronic engine should be fine and probably more efficient.

But you said a set, which to me implies twins. IMO, the redundancy of twins pretty much negates the question of reliability of the electronic engine.

I.like my tier 2 electronically controlled mechanically injected 4045TFM75 John Deere. Some of the best of both worlds.

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Old 08-20-2019, 08:54 PM   #6
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I'm with Dave. Common rail absolutely run better than the mechanicals. But a lightning strike can kill the CR computer. So if doing long passages, the reliability of the mechanicals becomes important. If just cruising locally, the common rail will be reliable enough.

I have done some research on fuel burn rates for both, they are not different enough to matter. In fact, some CR engines meeting latest NOx specs actually are worse on fuel than the older mechanicals. Can't just say the new tech is better on fuel, not always true.
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Old 08-21-2019, 12:19 AM   #7
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JD engines

I had that choice & here is what I decided.

I went with a mechanical JD 6068 - 174 HP engine. M-2 rating.

I have it in My Kadey Krogen 42.

1. - Reliability
2. - Fix-ability by me in the field was another big factor
3. - Parts availability where ever I might go was another big thing for me
4. - Ability for the engine to run with zero electrical power required
5. - Economy is also a factor, but this engine is more economical that the Ford Lehman I pulled out at same vessel speed, so the small difference in fuel economy to go the next step to electronic controls was a very small %, so not enough to give up the reliability & in field fix-ability & maintain-ability by me that I needed.


I have only one engine in my KK42 - not the scenario you were talking about, -- but a single engine is my reality I live with & I was making the decision about this with that in mind.

If it was twins I would go with two 4 cylinder JD engines.

Thanks.

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Old 08-21-2019, 02:08 AM   #8
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Electronic/electric sensors, controls and computer chips always eventually fail. Sometimes the engine still runs. You get really good fuel economy and less smoke with the engine stopped, but you don't go anywhere.
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Old 08-21-2019, 05:51 AM   #9
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IF I were crossing oceans I would have a robust single shaft , large slow turning prop and a landing craft style transmission that could use either or both engines.

I would choose a 3-71 and a 6-71 .

The 3-71 would be grand for passages that required 50-90HP to long range cruise,, the 6-71 would be used inshore , and both together where fuel is cheap and abundant.

Don't know how I would get a new boat past the air police to register it tho.
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Old 08-21-2019, 01:52 PM   #10
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As far as I know, you can put any engine in a recreation vessel. Commercial is where they screw you into using electronic engines.

And yeah, I'd have a Detroit 71 series for reliability. If you could find a Detroit dual transmission (2 engines on a single shaft) you could have any combination of 71 series. They also made quad setups. LCI(L) landing ships had two quads, each running a shaft. I ran a tug with a quad setup. You only had to start one engine with a starter and then the others were started by clutching them in.
And there are way to get better economy out of Detroit 2 cycles. I do.










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Old 08-21-2019, 02:18 PM   #11
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Iím in the mechanical camp. I like that there is the greater possibility Iíll be able to patch it and get going again with mechanical. Iíve been able to do that several times. And that the boat will keep going without electricity. Iíve weathered that also. That said, in my opinion maintenance of the engine(s), fuel system, soft parts (belts hoses etc) and drive train is going to matter more than potential electronic failure. There has been only one time Iíve needed to be towed. It was due to the failure of a soft part. The vibration dampening disc mounted between the transmission output flange and the shaft coupling flange. The failure was catastrophic and due to exceeding the designed life of the device.

I'm not been in the assistance towing biz but I've assisted quite a few. Without exception it was either fuel or soft parts that stopped the boat.
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Old 08-21-2019, 02:42 PM   #12
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I've a different take---

Millions of electronic diesels are produced every year. Tens of millions of electronic gas engines made every year too. These modern marvels have dramatically improved the internal combustion engine and strides continue to be made. Every Nordhavn, KK, Fleming, Cat truck, Komatsu loader etc made in the past decade or more are with all electronic diesels.

A century ago similar discussions were taking place when power boats were replacing sail boats. The tide changed a long time ago on the advantages of electronic engines. Sure a lightning strike can maybe do them in, but a much overblown straw man issue it would seem.

A lightning strike can do in all our eletronics too, but not one posting on TF stating the crying need for a sextant and RDF that I recall. In fact the very essence of TF is based upon the electronic age in which we live. Due to electrical wizardry, we can rail against electrical wizardry. Seems a dichotomy at play here.
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Old 08-21-2019, 02:52 PM   #13
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Quote:
Originally Posted by sunchaser View Post
I've a different take---

Millions of electronic diesels are produced every year. Tens of millions of electronic gas engines made every year too. These modern marvels have dramatically improved the internal combustion engine and strides continue to be made. Every Nordhavn, KK, Fleming, Cat truck, Komatsu loader etc made in the past decade or more are with all electronic diesels.

A century ago similar discussions were taking place when power boats were replacing sail boats. The tide changed a long time ago on the advantages of electronic engines. Sure a lightning strike can maybe do them in, but a much overblown straw man issue it would seem.

A lightning strike can do in all our eletronics too, but not one posting on TF stating the crying need for a sextant and RDF that I recall. In fact the very essence of TF is based upon the electronic age in which we live. Due to electrical wizardry, we can rail against electrical wizardry. Seems a dichotomy at play here.
While I understand what you are saying, you also need to consider self-maintenance and trouble shooting under way.

Using your truck and auto comparisons; I used to do a lot of engine work on my Mini Coopers and my Ford Escorts back in the day. I'm afraid to even look under the hood these days!
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Old 08-21-2019, 03:06 PM   #14
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Thanks for all the thoughtful replies. I am wondering if folks have an aides of what the value difference would be 0n average between an electronic version vs. mechanical version of the JD 6068, comparing two motors with similar hours and good maintenance histories. Seems that the electronic engine should be more, but how much more? 10%?, 25%? More?
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Old 08-21-2019, 03:25 PM   #15
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Quote:
Originally Posted by menzies View Post
While I understand what you are saying, you also need to consider self-maintenance and trouble shooting under way.

Using your truck and auto comparisons; I used to do a lot of engine work on my Mini Coopers and my Ford Escorts back in the day. I'm afraid to even look under the hood these days!
Just wrapping up a 3000 mile boat journey. As usual lots of self maintenance going on, such as filters, oil, batteries, recalcitrant AP pump motor, magnum inverter going on the fritz etc. but no dreaded lightning strikes! A friend with a KK 44 all electronic JD 6068 had to deal with an engine problem, yup not electrical, a raw water pump.

Recently bought a new car. Like you say, no owner maintenance possible. Bought an extended warranty.
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Old 08-21-2019, 04:22 PM   #16
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Boats last for decades. 1500 hours means that the engines are probably nearing ten years old. Electronic parts aren't produced forever so at some point replacement controllers will become a problem. Not that JD wouldn't want to supply them but the chip makers wont be making the chips so a redesign of the controller would be required. What maker will redesign a controller for an old engine?
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Old 08-21-2019, 05:56 PM   #17
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Good question. Some years ago I discussed legacy engines and electronics with Cat regarding off highway engines. They said that electronic controls are easy to update and or replicate as the decades roll on. Having experienced this first hand it was interesting to see control improvements made to existing engines to deal with longevity issues.

I just spent some time on a vessel that has recently gone through a rebuild on the 16V92s. Even the looms, field sensors, controllers and connections were redone if deemed "old". It all looked factory new. Point being, these two decade old DDECs have ongoing good support. Can't see JD being any different.
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Old 08-22-2019, 08:19 AM   #18
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"but not one posting on TF stating the crying need for a sextant and RDF that I recall."

I have often pointed out the most likely cause of an engine and massive electronics failure would be a small nuke 100-150 miles up.

Any small radio that still works is a crude MDF and if paper charts are on board contour nav (even if you have to heave too) with all the anchor lines end on end would give an EP, hopefully enough to find the shore and an inlet.

Most folks do not have the current book on board to even shoot a sun line, if they had a sextant.
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Old 08-22-2019, 08:19 PM   #19
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Definitely go Mechanical.
The dumbest thing is to put an electronic diesel in a marine environment. Probably ok for the street, but not for the ocean.
Iíve seen way too many electronic diesel boat owners SPEND THOUSANDS keeping their motors running. So much for saving a little fuel.....
Itís a great way for the engine manufacturers to make more money.....and other point is get 10 years down the line, you need some random sensor or electronic something or other and they tell you, ďoh Iím sorry, we donít make that part anymore. We do have an electronics upgrade package for you for $12,000Ē.
Give me a brake. Go mechanical!
Iíve never spent any money on any of my mechanical diesels other that impellers or filters. Usually completely bulletproof and the one piece of equipment that keeps on going.
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Old 08-22-2019, 09:00 PM   #20
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Cool

I have an old 3406 CAT that is all mechanical and is almost as old as I am.
The only thing it requires is clean fuel, engine oil, and filters.
It wont pass an EPA emissions test, and that is what started electronic controls in the first place.

If you ask me ( and no one cares what I think )

I will stay with the CAT mechanical engines every day of the year.
Because I am sure I will die before it does.
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