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Old 09-09-2012, 13:15   #16
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Re: Diesel Abuse?

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Originally Posted by Don Lucas View Post
I just let it run at idle for a few minutes to allow the various engine parts to equalize. The amount of time varies depending on how I was running the engine. If I had been running hard I will idle it for around 5 minutes (like the manual says), if I was just lightly running along I will pretty much just turn it off after 1-2 minutes.

If I was running in neutral to charge batteries, or if I had been running lightly for a while, I run the engine up to high rpms for 10-15 seconds and run it back down and repeat this a couple of times evry couple of hours. Then run a minute and turn it off.
I am mostly a club racer and neither I nor my compatriots do anything more than Don does. This has been my modus operandi since 1992 on 2 boats and I have yet to see any issues, nor I am aware of any such issues arising on my competitors boats. I am quite happy to help the environment and save my cash (put the savings in your 'diesel replacement a/c' if you must) and I still seem to sleep well at night (and occasionally in the afternoon).
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Old 09-09-2012, 14:08   #17
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Re: Diesel Abuse?

John Deere says my 80 HP model 4045 should not be in idle for more than five minutes at a time. Once warmed to operating temperature, I usually operate at an "easy" 1700-1800 RPM or "hard" at 2200 (theoretical maximum RPM is 2500 but governor limits it to 2400.) I keep the water temperature at its normal high of 180 degrees F. Run the engine at 800-1000 RPM to cool down engine at end of run for five minutes or less while approaching/operating in the marina to the berth.
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Old 09-09-2012, 14:55   #18
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Re: Diesel Abuse?

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John Deere says my 80 HP model 4045 should not be in idle for more than five minutes at a time.
I believe this is to stay in accordance with EPA instructions. I don't think it has anything to do with engine performance or longevity.
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Old 09-09-2012, 15:23   #19
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Re: Diesel Abuse?

Raku, the truckstop thing is not because of how diesels like to keep running, but actually (as taught by a combustion engineer with a long list of degrees and patent holdings) because truckers can't afford to shut down--and not start up again.

The traditional problems of "it won't start" and "I killed the battery" just don't happen if you leave the engine running. Starting an engine, any engine, puts wear on the starter and alternator and spikes the electrical system. So if a starter is good for 5000 starts, it doesn't matter if you leave the engine running 24x7, it is still "each start" runs up the clock on the next starter failure, and the next lost delivery. Ditto for the electrical system, starters throw a 2000V spike in trucks. 600V in cars. Also, if you start and run only a short time, you leave condensation in the exhaust system, which rots that out, and in the engine oil, which causes oil, bearing, other failures. And every time you start, the bearings slam around until oil pressure builds, bringing bearing failure or more frequent overhauls around sooner. Once there's oil pressure and the engine is running properly (any engine) there's zero wear, compared to what happens during starting.

And of course with conventional oils, every time you shut down the engine, some of the oil cokes up and forms tars as it cooks, uncooled, on the valve covers and in other places. But that problem is better called "someone's too cheap to run synthetic oil" these days.

Yes, a diesel likes to run "steady state" but truckers leave them running to avoid all the other problems that starting causes. Every time you hit the starter, the whole system gets "abused" compared to just burning fuel. Fuel is cheap--even at today's prices, compared to the other choices.

On boats? The starting issues still apply, our starters still have a limited number of starts in them. And the moisture problems (oil, exhaust) are still there, although with wet exhausts they're a bit different. Mainly, you need to run long enough to dry out the oil (20-30 minutes?) and with enough load to prevent carbon buildup. The spikes can be clamped or avoided (should be in any case) and the number of starts on a typical starter, well, if it doesn't last 30 years maybe that's acceptable anyway. <G>
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Old 09-09-2012, 15:38   #20
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All internal combustion engines are designed to have maximum durability when they run at their normal operating temperature.

Maximum wear occurs on startup due to the short delay until oil pressure builds and pressurised oil is flowing to all the internals.

Engines not allowed to reach and maintain normal operating temperature tend to see acidic by products build up in the engine oil and exhaust.

Minimising starts and ensuring the engine can run at load for sufficient time is the key to longevity.

The advice to always run a diesel flatout should be taken with caution. Fire trucks have this issue where they run hard from cold. Engine life is reduced if any IC engine is subject to high load before it has reached a stabilised operating temperature. Extended running at idle can also lead to glazed bores and increased oil consumption and blowby.

Clean air, fuel and oil are also vital.
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Old 09-09-2012, 15:54   #21
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Re: Diesel Abuse?

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I've heard these arguments for running the diesels like this for years. But I've yet to have it explained to me in a way that I understand just what it is about diesel engines that makes it better to run them. They don't get hot enough for temp to really be that much of a factor. As far as varnish, does diesel evaporate and varnish up like gasoline does? it's not that volitile, is it? Diesel fuel has a long shelf life. It's also a preservative and lubricant.

If the engine is running, aren't the parts subject to wear and friction that doesn't happen when it isn't running?

The engine life and time between overhauls is expressed as hours since last overhaul.

If that number is, for example, 10,000 hours, I never see someone spec it as "10,000 hours IF you run it all the time and only 5,000 hours if you don't run it".

When I google up "why do truckers leave their trucks idling" I get opinions but no hard facts other than that they like to leave all their systems running while they are sleeping, or they are only stopped for a short time and it's bad to let them cool off and then re-start them an hour later and let them have to warm up again. That isn't valid for boats. Sounds like their issue is restarting them too soon after lunch. Not days later when returning to port.

I'd like to understand it, as we just bought our first boat with twin diesels in it. They have about 3,000 hours on them, and are 26 years old.

You need to talk to a certified marine disesel. That was my source, and I believe it.
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Old 09-09-2012, 16:01   #22
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Re: Diesel Abuse?

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Don, How do you cool it down, and why? I just shut mine off and never thought of doing it otherwise. I have heard that engines get hotter when you stop them, but how do you avoid that?
I slow down as I come in the marina and leave it running in neutral for a few so the water can pump through it without a load before shutting it off.
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Old 09-09-2012, 16:33   #23
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Re: Diesel Abuse?

what I am seeing from the truck drivers here agrees with what I am reading online. Truckers leave the diesels idling for a set of reasons that do not really parallel those on a boat.

Some of these 'urban myth' ideas remind me of how many years I read that we needed to drink 8 glasses of water a day. Come to find out, it was a totally made up myth with no scientific or medical basis whatsoever.
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Old 09-09-2012, 18:03   #24
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Re: Diesel Abuse?

Pros & Cons

- Short runs - Temperatures in the metals do not stabilize. Different parts of the engine have expanded at different rates. This may or may not cause increased wear on bearing, piston skirts and other parts of the engine. In extreme cases going from cold to high power can warp cylinder heads.

- Low power - The fuel is not likely being burned at 100% efficiency. This allows unburned fuels to deposit more readily as soot in the exhaust system. Extreme level of soot can block the exhaust and cause power problems. Idling for long periods in a boat engine is not a great thing to do.

- Condensation - When warm air contacts cool surfaces it can create condensation. The vapors in the crankcase are pretty nasty. Lots of short runs allow water vapor in air to condensate internally and water mixed with the oil vapors can cause corrosion. A longer higher temperature engine run will "boil" water out of the oil system.

- Although the environment that marine diesels operate in is pretty tough with salt water cooling and the salt water environment the average diesel in a boat has it pretty easy in terms of duty cycle. I do think you lose half your engine life with short runs or low power operation but if the engine is rated at 3,000 rpm you aren't doing it any favors operating at 2,000 rpm. However the engine/prop combination may be more efficient at this RPM depending on torque curve, fuel flow, hull length etc. That is if the boat is somewhat overpowered adding RPM just adds fuel flow not hull speed.

In this case the fuel savings over 5,000-7,000 hours needs to be weighed against any shortened life the engine may experience.

Like just about everyone who owns a sailboat, I run my engine relatively short periods (10-15 minutes mostly) and at lower RPM (2,200-2,400) with periodic high power runs to blow out the cobwebs..

I wouldn't stress about it too much.
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Old 09-09-2012, 18:14   #25
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Re: Diesel Abuse?

[
Quote:
QUOTE=hellosailor;1032714][I][U]Raku, the truckstop thing is not because of how diesels like to keep running, but actually (as taught by a combustion engineer with a long list of degrees and patent holdings) because truckers can't afford to shut down--and not start up again."
I disagree with that. I managed fleets at CRST and J.B. Hunt 1500 and 2800 prime movers respectively. Way more expensive to run engines and pay for fuel and wear and tear. APU's and Idle Air becoming more and more common.


Quote:
The traditional problems of "it won't start" and "I killed the battery" just don't happen if you leave the engine running. Starting an engine, any engine, puts wear on the starter and alternator and spikes the electrical system. So if a starter is good for 5000 starts, it doesn't matter if you leave the engine running 24x7, it is still "each start" runs up the clock on the next starter failure, and the next lost delivery. Ditto for the electrical system, starters throw a 2000V spike in trucks. 600V in cars. Also, if you start and run only a short time, you leave condensation in the exhaust system, which rots that out, and in the engine oil, which causes oil, bearing, other failures. And every time you start, the bearings slam around until oil pressure builds, bringing bearing failure or more frequent overhauls around sooner. Once there's oil pressure and the engine is running properly (any engine) there's zero wear, compared to what happens during starting.
Once again we disagree. There is no way that a 12V or 24V system puts a voltage spike through a starter. Amperage draw can reach those levels.

Quote:
And of course with conventional oils, every time you shut down the engine, some of the oil cokes up and forms tars as it cooks, uncooled, on the valve covers and in other places. But that problem is better called "someone's too cheap to run synthetic oil" these days.
See my comment about oil sampling programs and turning trucks back in with 400k that never had an oil change. All dino no synthetic.


[/QUOTE]
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Old 09-09-2012, 18:25   #26
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Re: Diesel Abuse?

If you really want to join the "Big Boys" install a pre-oiler, this little gizmo will run your oiling system up to full pressure prior to starting the engine.
It is at this time (starting where the majority of wear and damage happens) the pre-oiler will extend the life of your engine when nothing else will.

Also,,when you run an engine up through the revs and put a good load on her, you will prevent ridge buildup inside the cylinder (metal deposits at the very top of the cylinder bore where the piston ends its sweep) which will break the rings if left too long and you run the engine past any normal rpm.

Two minute warm up,,,,and one minute idle down has been the handy rule with most fleets.
Also ...just a wee tidbit for ya.....A true diesel engine does not require any electrical power to continue running,,just fuel and oil.
Which is why the Diesel trumps all other engines in reliability and performance amongst other things.
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Old 09-09-2012, 18:32   #27
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Re: Diesel Abuse?

Most truckers leave there engines running because they like to SLEEP in comfort! either cooled or heated ! Not for any starter or starting thing ! Any engine useing diesel, needs to be run at the proper temprature, usealy at 180 degs F not C LOL if ya make sure ya get the temp up to factory specs. as far as cooling down a diesel, if it has a turbo it's absolutely nessary !! slowly reducing rpms down to an idle, and letting it breath for 5 for 6 minutes will do it ! and it will save ya some time later haveing to clean your oiled up turbo! Most diesels Last better if ya dont run at or even near max revs for very long !! I don't care what your mech told ya !! Ive run the perkins in my boats at a max of 1850 for years and have had as many as 8000 hours on a couple of them, with no major repairs needed!! I change filters and oil at no more then 150 hours of running, or once every 6 mos if not run that much !! they are not gas engines! They need to be run at temp and have good maintaince! valves adjusted, oil leaks fixed, and CLEAN fuel! I will continue to run my diesels this way cus its worked for me !! for over 40 yrs Just my 2 cents
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Old 09-09-2012, 18:43   #28
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Re: Diesel Abuse?

As Bob and Connie point out above: CLEAN FUEL. Most diesel engine problems by far are fuel related (Marine engines). And these fuel problems are getting worse as we get crappy fuel shoved at us.

Many truckers run their rigs full time in the winter to keep the fuel in their tanks warm (although I see insulated tanks on the newer tractors). If the fuel gets cold it tends to gel (bio diesel).
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Old 09-09-2012, 18:53   #29
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Re: Diesel Abuse?

like Bob&Connie said and Ex-Calif consistency is your best friend when it comes to diesels.
Which is why large fleets such as Grey-Hound have had units run Two Million Miles before tear down.

Think about that....Two Million Miles averaging 50 mph..covert that into hours running,,so you must figure we must have been doing something right.
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Old 09-09-2012, 19:35   #30
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Re: Diesel Abuse?

Hay Nemo were those Detroits ?? They last forever if run right and maintained right!! Our new to us ketch has my all time favorite 471 7000 type with 160 hp 2 stroke! with 600 gal fuel tanks! gives us a Bunch of range if needed!! Ya just can't beat a Detroit for long service and fuel mileage!! And ya can get parts anywhere most anytime !!
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