# Lifespan of a Diesel Engine



## saltydog4 (Dec 22, 2014)

Simple question that I'm sure has been asked before. What is the average life expectancy of an inboard diesel that has been well maintained? Measured in hours, not years.


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## Dave_E (Aug 7, 2013)

I've got almost 3500 on my original 1979 Universal 5425... puffs a mere wisp of smoke at startup. But to answer your question, the answer I got the most when asking this question was: somewhere in the neighborhood of 5000 hours for any appreciable work, life of 10.


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## jerryrlitton (Oct 14, 2002)

I have over 5900 on my Perkins 108.


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## MarkSF (Feb 21, 2011)

saltydog4 said:


> Simple question that I'm sure has been asked before. What is the average life expectancy of an inboard diesel that has been well maintained? Measured in hours, not years.


This is one of those "how long is a piece of string" questions. To wear out could be anything from 5,000 to 10,000 hours, if used regularly and taken care of. I would venture to say that they rarely get replaced due to being generally worn out. What often kills them is some kind of accident where they get filled with water. Another problem is just obsolescence - lack of parts availability, especially for the marinised parts. As far as I know, the exhaust manifold is completely unavailable for the Universal 5424.

My 5424 has at least 3850 hours on it (I say at least, because the hour meter broke at 3,700, an unknown time ago.). I replaced it and have recorded another 150. No symptoms of wear.


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## saltydog4 (Dec 22, 2014)

I'm looking at a sailboat with a yanmar that has 3480 hours. Sounds like that is a lot.


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## RichH (Jul 10, 2000)

8,000 to 10,000 hours on a _well maintained_ Yanmar is not an unusual 'lifetime', especially the QM & GM versions.


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## aeventyr60 (Jun 29, 2011)

4800 hrs on a 20 year old Perkins 4108. I expect to get 10,000 ez.


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## BarryL (Aug 21, 2003)

Hey,

My o'day 35 had a Universal M25 with about 5000 hours on it. I sold the boat last July. Last I heard the engine was still running great.

Barry


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## travlin-easy (Dec 24, 2010)

My dad drove a diesel powered tractor trailer, beat the living hell out of the engine, and the first rebuild was at 350,000 miles and it was only a minor rebuild. I don't know what this translates to in hours, but it's a lot of hours. That was nearly 10 years of daily use and abuse.

Gary


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## eherlihy (Jan 2, 2007)

The average car needs an oil change every 5000 miles. The average car averages 35 MPH - on average (city/highway/stop & go). This averages out to an oil change every 142.8 hours, but I'll call it 150 hours.

I'm willing to guess that the tractor trailer's average speed was ~50 MPH (less city, more highway), which means that he had the first rebuild at about 7000 hours.


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## JimMcGee (Jun 23, 2005)

Most times when I hear of a diesel failure it's been overheated or ingested water.

Change your oil, belt, impeller, filters and keep the fuel clean and she should grumble along for many years. It really doesn't take much time to do.

The one thing I've never heard of is a motor dieing because it was too well maintained.


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## RichH (Jul 10, 2000)

travlineasy said:


> ..............and the first rebuild was at 350,000 miles and it was only a minor rebuild.


350000mi ÷ ~50 mph (average) = 7000 hours. .... that's about the right time for a head/valve job, etc. 'rebuild' on an 'oil burner'.


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## mike dryver (May 13, 2006)

Actually a truck diesel isn't broken in until about 40000 miles, or 1000 hrs, break in time. Truck engines if maintained well, will run over a million miles before needing major rebuilds. At least the old 1s I drove did. That would be 60s, 70s, 80s, and to mid 90s. Todays engines run better, and hotter, because of computers, but are built lighter for weight savings, ie better fuel economy. Also there is a lot of plastic, and aluminum on them. the engines hours should not dictate when it is time for a rebuild/repair. That is or should be dictated by the maintenance it has received, and or any issues that crop up during use, and how fast you can react to the problem, before you do damage!!!!!!


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## MarkSF (Feb 21, 2011)

saltydog4 said:


> I'm looking at a sailboat with a yanmar that has 3480 hours. Sounds like that is a lot.


IMHO, an engine with those hours could have years and years of life left, or be ready for the scrap heap, depending on many factors. An engine survey will tell you which one is the case.


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## rdw (Jan 14, 2010)

What is done in an engine survey? I am thinking if it is very invasive you might be better off to done some replacement work while it is apart.
Is there a good no invasive way to tell much?
Is an oil analysis worth anything?
I am thinking of doing the World ARC and my Yanmar (51 horse) has about 5,000 hours. It has been will cared for.
rdw


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## Waltthesalt (Sep 22, 2009)

A big factor in reducing life is not running the diesel at power. Running for short periods and not letting it to get to temperature causes early failures.


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## pikesbayone (Jul 25, 2013)

I did some research a while ago and came up with 10,000 hours. That was for a fresh water cooled small to medium sized normally aspirated diesel in an auxiliary sailboat application. I would expect less life for raw water cooled and less for turbocharged engines. For my friend who asked the question that worked out to about 100 years, as he only used his engine to get out of the slip and motor to the harbor entrance on most days.


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## PaulinVictoria (Aug 23, 2009)

His will likely last a lot less then, diesels like to be warm and working hard for long periods of time.


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## mbianka (Sep 19, 2014)

In 2007 my diesel died at 1900 hours despite regular maintenance, oil changes every 50 hours or yearly which ever came first etc.... Leak in head gasket sprayed water onto a cylinder and cracked it. Spent a lot of money trying to figure out why a formally good running diesel would not suddenly start. As others have said diesels do best when run long and hard. On sailboats they tend to rust out rather than wear out. Instead of a rebuild or replacement diesel I converted to electric propulsion and never looked back. It has been a much better fit with how I use my "sailboat" than with the diesel.


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## Classic30 (Aug 29, 2007)

FWIW, my boat has had three engines in 60 years - one every 20 years, more or less. That's for an auxiliary sailboat in and out of the dock with the occasional long run.

It's the marine (salt air) environment that gets to them in the end, not so much how often it's used although that plays a part. It seems rusting from the outside due to sitting at the dock or rusting from the inside due to breathing lots of salt air makes little difference in the end.


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## ReefMagnet (May 8, 2008)

Industrial diesels using pretty much the same motors as found in many boats run somewhere between 8000 and 12000 hours if not longer in some cases. However, these engines tend to run continuously and at constant speeds rather than in the smaller bursts as happens on sail boats. I'd really think that time/corrosion is the killer on a boat engine assuming that water ingress doesn't do it first.


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## Minnewaska (Feb 21, 2010)

Here's the way I see it.

If you start with a brand new diesel, maintain it very well and run it properly, you will get substantial life out of it. 

However, buying one run by another is a crap shoot. Whether with 500 hrs or 5000 hrs. First, they need to be broken in by running them very hard. That's counter intuitive, so some owner may baby their new motors, which can improperly seat the rings to the piston walls. You can't know. You can't tell how often oil was changed (the smartest thing you can do is change it frequently, even if you don't do the filter). 

The good news is, diesels are pretty simply mechanical devices. A good mechanic (although very hard to find) can generally diagnose the current condition of a motor. Compressions, noises, smoking, oil analysis for metal wear (must be done after running at sea for a while), etc. Wear items can be replaced: belts, hoses, exhaust elbows, fuel filters, etc. Cooling passages can be descaled, tanks can be cleaned, etc. What they can't do, is tell you how well it was routinely maintained, therefore, how long it will likely last. 

The further problem with diesel surveys is many aren't worth a cent. They visually inspect, fire it up at the slip, run it for 15 mins, take a compression and send you a bill. If you are getting one at all, they need to take a few things off to see inside, such as the elbow for starters.


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## Don L (Aug 8, 2008)

Waltthesalt said:


> A big factor in reducing life is not running the diesel at power. Running for short periods and not letting it to get to temperature causes early failures.


I agree. Other than overheating I bet the biggest killer of inboard diesels is "kindness".


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## aeventyr60 (Jun 29, 2011)

Don0190 said:


> I agree. Other than overheating I bet the biggest killer of inboard diesels is "kindness".


Yes, run it often, run it hard, torture it a bit...regular oil changes, clean fuel and she'll run a long long time. Warp speed, Scotty....


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## RichH (Jul 10, 2000)

Most industrial 'prime mover' diesel engines are usually selected/operated at ~75% of max. rpm so to obtain maximum service life. The same approx. 75% of max rpm is the design selection on most boat diesels. 

Running hard and often for a cast iron marine engine allows a thick internal buildup of 'black' or ferrous rust which is protective. Over time of long term inactivity the black rust will convert to destructive 'red' / ferric rust. So, if shutting down for long periods of time consider to add antifreeze containing anti-rust compounds to preserve that black rust. Draining a cast iron engine for long term layup accelerates the formation of 'red' rust, which may be the severe form of 'red' rust - *SLAB rust* which are huge 'platelets' of red rust which can 'push apart' the natural stratifications in the cast iron casting.


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## skalashn (Jun 28, 2011)

Mercedes-Benz museum in Germany has 1988 200D with 1.9 million km on the original diesel. Used as a taxi in Portugal. Assuming 50 km/h average, which is probably generous for a taxi, this is 38000 hours.


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## SkywalkerII (Feb 20, 2008)

The comments suggesting that hard use, full warm up have been echoed by every diesel mechanic I've known. 

It is ironic that most sailors use their engines to get in and out of the harbor, in short bursts and not fully warmed up. 

Without trying to start an alternate discussion (or fight!), this is a good argument for the good old Atomic 4 gas engine. Gas engines do well the manner many sailor use their auxiliaries - short duration, on/off...which is why their are many 30-40 year old A4s still out their, mine included.

Skywalker
1966 Tartan 27
Original A4


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## Faster (Sep 13, 2005)

Waltthesalt said:


> A big factor in reducing life is not running the diesel at power. Running for short periods and not letting it to get to temperature causes early failures.


Unfortunately the above scenario is an almost perfect use of a *sailboat's* auxiliary engine...


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## zedboy (Jul 14, 2010)

Question for the class: what's considered best practice, considering you _are_ going to run for just a few minutes to get in or out? Let it warm up at idle at the slip till the temp gauge jumps? Warm up at a fast idle? Screaming idle?

Buy a long shaft two-stroke kicker that will take infinite abuse for marina maneuvers and save the diesel for motor passages?


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## Minnewaska (Feb 21, 2010)

I warm up for at least 15 minutes at the slip, to get to temp. Easy to do, while other cast off tasks are underway. Once clear of the harbor, I usually open her up to position myself in the best spot for the first tack. Why not. Good for the motor, less goofing around and off I go.


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## UnionPacific (Dec 31, 2013)

saltydog4 said:


> Simple question that I'm sure has been asked before. What is the average life expectancy of an inboard diesel that has been well maintained? Measured in hours, not years.


It has everything to do with RPM. If you are running 3000RPM non-stop you may get 3000 hours. If you do not go over 2000rpm on the same engine you may see 5000 hours.
Some engines are designed for lower RPM then this, and those can last over 12,000 hours.
Maintenance plays a big part too, but you only need to change your oil every 500 hours to be in good maintenance. Some engines also require you check valve lash, keep up on this, the engine will thank you.


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## Minnewaska (Feb 21, 2010)

UnionPacific said:


> It has everything to do with RPM. If you are running 3000RPM non-stop you may get 3000 hours. If you do not go over 2000rpm on the same engine you may see 5000 hours......


I'll assume these were not intended to be specific RPM recommendations, since they vary by engine, rather just a point. Nevertheless, I think they could misinform. Lower rpm is not better in the absolute, or idling would be best and that's clearly not the case.

As a general rule, 80% of max rated rpm is usually in the range of the highest continuous rpm that a marine diesel should be run (always check your specific engine spec). If your 3000rpm example was 80% of max, then 2000rpm would be 53% of max rated. Running a diesel that low for continuous periods is not good for the motor. 60% of max is generally minimum and closer to 80% is better.

If you meant that 3000rpm was max, then 2000rpm would be 66% and clearly better than wide open throttle, while within proper operating range.

On a related point, one should always check that their boat will actually make almost exactly max rpm at wide open throttle when underway in calm seas. I allow for maybe 75rpm variance for tachometer error. You only need to hold it for about 10-15 seconds. Too high or too low is typically an issue with the propeller pitch, but it will also mean your motor is running with too much or too little load. Like peddling uphillin too high a gear or downhill in too low. It can also diagnose a problem with your motor generating the proper power. It's a spring commissioning (while the prop is nice and clean) checklist item for me every year.


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## UnionPacific (Dec 31, 2013)

Minnewaska said:


> If your 3000rpm example was 80% of max, then 2000rpm would be 53% of max rated. Running a diesel that low for continuous periods is not good for the motor.


Not exact examples, but lower is generally better. Load is more important then rpm when it comes to the speed being ok or not. The engine needs to be under enough load to keep the engine from losing heat at 2000 rpm for it to work well. 
For an example I try to run ours at 1800RPM, even thou our max RPM is 3200. This is only 50% of max rated, but the engine will last a very long time run at this RPM as it keeps the heat very well. The slower you turn your engine, under load, the better it is.
(This only applies to non-egr, IDI engines)
Idle is fine too. Many an old wise tail about running at idle, cylinder washing, and short engine life, however in some cold places engines idle 24/7 and are only put under load a few times a week. They have been seen to be beyond 12,000 hours on a regular basis. My last on road diesel was idled for over 4000 hours alone, it would get so cold I had to bump up the idle to keep the engine warm. It had no obverse effects. Industrial, IDI non-turbo engines are built loosely, and can do all sorts of crazy things. Running slow is best on these old tech engines. The sea water will kill them long before running them slow will.
I would recommend as long as your engine temp is not dropping, to go as slowly as you can stand. This will lengthen the life of the engine. 190-200 minimum temperature. typically you want to aim for you maximum torque sweet spot. If you can find a power curve for your engine look at where torque is maxed, and keep your RPM there. typically this is around 1800RPM.


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## IStream (Dec 15, 2013)

UnionPacific said:


> Not exact examples, but lower is generally better. Load is more important then rpm when it comes to the speed being ok or not. The engine needs to be under enough load to keep the engine from losing heat at 2000 rpm for it to work well.
> For an example I try to run ours at 1800RPM, even thou our max RPM is 3200. This is only 50% of max rated, but the engine will last a very long time run at this RPM as it keeps the heat very well. The slower you turn your engine, under load, the better it is.
> (This only applies to non-egr, IDI engines)
> Idle is fine too. Many an old wise tail about running at idle, cylinder washing, and short engine life, however in some cold places engines idle 24/7 and are only put under load a few times a week. They have been seen to be beyond 12,000 hours on a regular basis. My last on road diesel was idled for over 4000 hours alone, it would get so cold I had to bump up the idle to keep the engine warm. It had no obverse effects. Industrial, IDI non-turbo engines are built loosely, and can do all sorts of crazy things. Running slow is best on these old tech engines. The sea water will kill them long before running them slow will.
> I would recommend as long as your engine temp is not dropping, to go as slowly as you can stand. This will lengthen the life of the engine. 190-200 minimum temperature. typically you want to aim for you maximum torque sweet spot. *If you can find a power curve for your engine look at where torque is maxed, and keep your RPM there.* typically this is around 1800RPM.


Your point about running at peak torque is a good one for any engine but you're over-generalizing about the RPM. My (turbo) Yanmar 4JH3-HTE has a max RPM of 3800 but peak torque is at 2900.


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## nolatom (Jun 29, 2005)

45, 50 years, if fresh-water cooled?

Witness "Elmer", the original engine on the Coast Guard Barque EAGLE:

USCGC Eagle (WIX-327) - Wikipedia, the free encyclopedia

You could probably do much longer if parts were available, but typically they're not when they get that old.


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## Minnewaska (Feb 21, 2010)

UnionPacific said:


> Not exact examples, but lower is generally better. Load is more important then rpm when it comes to the speed being ok or not. The engine needs to be under enough load to keep the engine from losing heat at 2000 rpm for it to work well.
> For an example I try to run ours at 1800RPM, even thou our max RPM is 3200. This is only 50% of max rated, but the engine will last a very long time run at this RPM as it keeps the heat very well. The slower you turn your engine, under load, the better it is.
> (This only applies to non-egr, IDI engines)
> Idle is fine too. Many an old wise tail about running at idle, cylinder washing, and short engine life, however in some cold places engines idle 24/7 and are only put under load a few times a week. They have been seen to be beyond 12,000 hours on a regular basis. My last on road diesel was idled for over 4000 hours alone, it would get so cold I had to bump up the idle to keep the engine warm. It had no obverse effects. Industrial, IDI non-turbo engines are built loosely, and can do all sorts of crazy things. Running slow is best on these old tech engines. The sea water will kill them long before running them slow will.
> I would recommend as long as your engine temp is not dropping, to go as slowly as you can stand. This will lengthen the life of the engine. 190-200 minimum temperature. typically you want to aim for you maximum torque sweet spot. If you can find a power curve for your engine look at where torque is maxed, and keep your RPM there. typically this is around 1800RPM.


Comparing marine aux engines to truck engines to heavy equip or even gensets is false logic.

I just hope no one reads your absolute advice on rpm and believes it. Lower is not always better and 2000 is certainly not always the right number, nor is 1800 typically max torque. Part of the issue here is that marine engines only run in one constant gear, but I have a feeling it isn't worth debating.


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## JimMcGee (Jun 23, 2005)

Actually I have to wonder how much of this has become "tribal knowledge" repeated on sailing forums that may in fact be incorrect.

This thread piqued my curiosity so I went and re-read the operator's manual for my diesel engine (25hp Universal).

The section on break in procedures recommends against extended idling (but only during break in), info on proper oil, filters, coolant, etc. But *not a single mention of operating a diesel at a specific load*. If it was truly that important in maintaining the life of an engine you would think Universal would mention it in the manual.

I spent a lot of time in truck cabs when I was in college, and those trucks spend a LOT of time idling. A diesel is not a gentle thing. Be religious about the maintenance, change the oil, filters, impeller, belts, motor mounts (every few years). Don't over heat it and don't over think it and you'll be OK.


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## ReefMagnet (May 8, 2008)

The problem with extended idling and light loading on a diesel engine is that it increases the possibility of glazing the bores. A number in my head is 80% max rpm for loading the diesel. I personally prefer to run my marine engine with it's spec'd 3000 max rpm at 2400 rpm with occasional bursts up to 2700 rpm and the odd run at around 1800 rpm just to keep it varied. I actually worry more about the carbon buildup in the exhaust elbow which seems to plague a lot of marine diesels and I assume this increases if run to lightly loaded (cold) or too heavily loaded (over fuelling).


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## UnionPacific (Dec 31, 2013)

IStream said:


> Your point about running at peak torque is a good one for any engine but you're over-generalizing about the RPM. My (turbo) Yanmar 4JH3-HTE has a max RPM of 3800 but peak torque is at 2900.


Your engine is DI, and turbo, as I said above IDI non-turbo only.


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## UnionPacific (Dec 31, 2013)

Minnewaska said:


> Comparing marine aux engines to truck engines to heavy equip or even gensets is false logic.
> 
> I just hope no one reads your absolute advice on rpm and believes it. Lower is not always better and 2000 is certainly not always the right number, nor is 1800 typically max torque. Part of the issue here is that marine engines only run in one constant gear, but I have a feeling it isn't worth debating.


Not worth debating as most industrial engines run at a set speed all day. Also many boat engines are from cars, or trucks. I have run industrial engines far beyond what anyone would run a boat. trust me, I am a diesel god.


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## JimMcGee (Jun 23, 2005)

ReefMagnet said:


> The problem with extended idling and light loading on a diesel engine is that it increases the possibility of glazing the bores.


Reef, I've heard this before and if you hear it enough you believe it must be true.

But when I look at the manual for my engine it only mentions glazing the bores as a potential problem during break in prior to the rings being seated.

Walk through any truck stop in a cold climate at night. Every truck is idling for hours on end. My engine is based on a Kubota tractor engine. Heavy equipment and farm equipment also idle for extended periods. Long term cruisers run their engines to charge batteries.

If any of the behaviors actually harmed engines wouldn't the manual call it out in big bold print?

As long as you use the engine a bit to blow it out after extended periods of idling you're probably fine.


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## Don L (Aug 8, 2008)

My manual says it is Ok to idle the engine, just every couple of hours to rev it up to 3000 rpm a couple of times.

I get the feeling that not many people ever read their manuals and instead follow myths.


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## Advocate777 (Sep 28, 2010)

RichH said:


> Most industrial 'prime mover' diesel engines are usually selected/operated at ~75% of max. rpm so to obtain maximum service life. The same approx. 75% of max rpm is the design selection on most boat diesels.
> 
> Running hard and often for a cast iron marine engine allows a thick internal buildup of 'black' or ferrous rust which is protective. Over time of long term inactivity the black rust will convert to destructive 'red' / ferric rust. So, if shutting down for long periods of time consider to add antifreeze containing anti-rust compounds to preserve that black rust. Draining a cast iron engine for long term layup accelerates the formation of 'red' rust, which may be the severe form of 'red' rust - *SLAB rust* which are huge 'platelets' of red rust which can 'push apart' the natural stratifications in the cast iron casting.


So , are you saying that when I buy my boat, all other things being equal, it is significantly better to buy a boat whose engine has been in recent regular use as opposed to one that may have less hours but which has been sitting at the dock unused for a year? Is there a time frame as to 'how long has this boat (engine) been sitting here unused?'


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## JimMcGee (Jun 23, 2005)

don0190 said:


> my manual says it is ok to idle the engine, just every couple of hours to rev it up to 3000 rpm a couple of times.
> 
> I get the feeling that not many people ever read their manuals and instead follow myths.


+1


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## aeventyr60 (Jun 29, 2011)

*


UnionPacific said:



Not worth debating as most industrial engines run at a set speed all day. Also many boat engines are from cars, or trucks. I have run industrial engines far beyond what anyone would run a boat. trust me, I am a diesel god.

Click to expand...

*Oh No, another internet false prophet. Let's all get on our knees for this one...


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## outbound (Dec 3, 2012)

Still question remains what is best behavior for turbo diesels to prolong life. Unaware of any non turbo diesels being used above ~50hp.


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## RichH (Jul 10, 2000)

Advocate777 said:


> So , are you saying that when I buy my boat, all other things being equal, it is significantly better to buy a boat whose engine has been in recent regular use as opposed to one that may have less hours but which has been sitting at the dock unused for a year? Is there a time frame as to 'how long has this boat (engine) been sitting here unused?'


Obviously one does not dismantle a marine engine to inspect for internal corrosion. The amount of internal rot and corrosion are the result of either storage with anti rust compounds in the water passages versus the other extreme of improper high humidity air inside the block/manifold - most of which is determined by questioning the owner of exactly how the engine was prepared for long term layup. 
If doubts are encountered - To assay (if engine condition assay is included in a purchase agreement) is usually by removing a manifold attachment bolt or other fastener which is in contact with the water passages inside the engine block, going into the bolt bore and counting the number of threads remaining and compare the number of threads to a new engine - to determine the extent of the internal corrosion and the remaining 'thickness' of the engine block. 
Also since exhaust manifolds in older engines are increasingly obsolete and unobtainable; a further step (if there is a high index of suspicion) would be the removal of the manifold for the inspection for evidence of internal slab-rust, examination for 'casting repair' - evidence of 'brazing' to 'patch repair' pin holes, etc. 
This of course would be in addition to any testing of mechanical function, such as a high pressure 'leak down' test to assay the integrity of piston rings and valve train, etc.; plus, a historical interrogation of at which rpm the engine was normally operated to determine if of not the engine was 'lugging' - operated at extreme combustion pressures due to being under-propped (pitch too high) which would suggest more than normal wear of the piston/connection rod pins, piston slap/scuffing of the cylinder walls, etc. .... and of course direct visualization of the propeller pitch. All this compared to a properly set up engine with "correctly matched" prop. etc. etc. etc. etc. ... including a paper trail/log of maintenance. 
All this leads towards indicators of current engine 'health' and mechanical integrity, are not an absolute; but, do raise or lower your suspicion of the remaining value of the engine. 
Having all such evaluations performed by a _knowledgeable_ engine mechanic can be expensive. Most boat buyers rarely evaluate a boat's engine, and simply look at the engine 'cleanliness' and condition of the engines paint as an indicator of the engines viability. 
All judged against the cost of a total engine replacement (~$11K - $14K for a 30-40ft. boat). :-|


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## IStream (Dec 15, 2013)

outbound said:


> Still question remains what is best behavior for turbo diesels to prolong life. Unaware of any non turbo diesels being used above ~50hp.


Same as a non-turbo except that it's good practice to let her idle for 5 min or so after a hard run to let the turbo cool down. If you shut her right down, the oil in the turbo bearings can cook.


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## alaska67 (Jan 3, 2008)

UnionPacific said:


> . I have run industrial engines far beyond what anyone would run a boat. trust me, I am a diesel god.


now you are a diesel god? uke

from what i have read in your postings you are sailnets most likely candidate to repeat a louis jordan.


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## Don L (Aug 8, 2008)

The real proof that a boat diesel engine will last a long time, even if you abuse it, are charter boats. Those always have a lot of hours on them and I bet the weekly charter person isn't giving it much thought as to making it last beyond that week.


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## ReefMagnet (May 8, 2008)

JimMcGee said:


> Reef, I've heard this before and if you hear it enough you believe it must be true.
> 
> But when I look at the manual for my engine it only mentions glazing the bores as a potential problem during break in prior to the rings being seated.
> 
> ...


When I worked for a company years ago that made thousands of generators annually using a range of various Perkins, Lombardini and Kubota diesel engines it was a known potential problem with lightly loaded machines and customers would be advised of such in the operator manual. Another issue (and it could very well be related) with extended idling is that the oil control rings can stick due to carbon build up and this is probably why your manual recommends a burst of speed every now and again to "blow out the carbon".


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## JimMcGee (Jun 23, 2005)

In a way we're saying the same thing.

Typical operation would include running the engine normally after idling. Lets say you charge your batteries once or twice at anchor. Running your motor to raise your anchor and clear the anchorage before raising sail would clear out the carbon. But you wouldn't have to run the engine up to red line to do it.

Our slip is close to the bay and we don't motor far before raising sail. Every so often I'll motor a little way down the bay to blow out any carbon build up. I don't think you have to worry much beyond that.


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## UnionPacific (Dec 31, 2013)

aeventyr60 said:


> Oh No, another internet false prophet. Let's all get on our knees for this one...


It makes no difference to me what happens to your engine. Go ahead, spin it fast until a main bearing goes out. In the here and now I will offer my advice, that I get paid to use elsewhere, here for free to those wanting help. Keep your attacks in PRWG.


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## aeventyr60 (Jun 29, 2011)

^Those that are claiming to be gods in the good pages of sailnet, might want to keep those dubious claims over in the sewer.


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## Don L (Aug 8, 2008)

I wonder what the proper sacrifice is and what the protocol of doing it is for a diesel God. 

Virgin extra sweet crude oil maybe?


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## alaska67 (Jan 3, 2008)

UnionPacific said:


> It makes no difference to me what happens to your engine. Go ahead, spin it fast until a main bearing goes out. In the here and now I will offer my advice, that I get paid to use elsewhere, here for free to those wanting help. Keep your attacks in PRWG.


 a well respected marine author that boat owners might actually consider a real expert on the subject of diesels disagrees with a sailnets "god". oh my

you type as a god on every subject you speak on but are far from it. i would caution sailnetters to take your advice with a decent grain of salt.

go find us some real sources from marine engine makers to back up your claims please


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## desert rat (Feb 14, 2013)

Extra virgin olive oil, no that laquers at high temperature.

Diesel engines like to idle warm, high idle to operating temp, run under load, high idle down to operating temp, and perhaps idle for a short cool down. Oil presure should never falter thus the perhaps on idleing at running temp.

The diesel i learned to love was a three cylinder 153 CI alluminun block with a blower. It would move a 5 ton, 6 wheel drive, anphibious vehicle, along at 65 MPH.


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## UnionPacific (Dec 31, 2013)

alaska67 said:


> a well respected marine author that boat owners might actually consider a real expert on the subject of diesels disagrees with a sailnets "god". oh my
> 
> you type as a god on every subject you speak on but are far from it. i would caution sailnetters to take your advice with a decent grain of salt.
> 
> go find us some real sources from marine engine makers to back up your claims please


Being an author does not make you knowledgeable. 
What is a marine engine maker? 
I am not aware of a single engine made for the marine environment under 200HP.
What they are is marine engine up-fitters, they take a diesel from a tractor, car, backhoe digger, or skidsteer and turn it into a marine diesel by adding an exhaust, raw water pump and heat exchangers. Not exactly a tough job.

My favorite marine engine line right now is Kubota. These engines are right out of the list I just gave you, and I have personally abused the crud out of them, and then fixed them. They are idled half the day, and the other half day abused to the point of stalling. Interesting noise the turbo makes when you stall at full throttle...
What is my point of all of this? I have spent more hours with my hands covered in diesel oil then most of you have spent motoring. I have seen what fails and what does not.

What fails? (IDI list) in order of fail rate: 
Fuel pump
Head gasket
injectors
valves
main bearings

(DI list)
Injectors
EGR
fuel pumps
turbos
head gaskets
Injectors taking pistons with them
heads (cracking)
main bearings

I say I am a diesel god because I know everything there is to know about them, I have done everything to them from valve lash to new pistons, I have hopped them up, and turned them down. I know what fails, and its not rings. Most marine engines seem to be taken out by water intrusion. Not from idling, and going the incorrect RPM. So save the fuel, and rev low. I am out of this thread.


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## Capt Len (Oct 9, 2011)

Oh,oh, looks like you've pissed him off! What'el we do now?


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## albrazzi (Oct 15, 2014)

My Diesel is 25 years old, runs like new and its a Volvo (gasp) rwc and a very simple machine. The guy 2 slips down got his running today after the boat sank in the slip. There are operational guidelines and that has surely been beat to death mixed with some luck and common sense. Bottom line they can and do last a very long time when the motor dies its usually from an ancillary source be it cooling or water intrusion anyway. The motor seldom just wears out at least in the marine environment. Too many other things to go wrong.


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## tdw (Oct 2, 2006)

Please keep a lid on the personal jibes. This isn't the sewer. 

I realise that the "diesel god" remark was a bit of a red rag to a bull but even so civility reigns in On Topic .


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## albrazzi (Oct 15, 2014)

tdw said:


> Please keep a lid on the personal jibes. This isn't the sewer.
> 
> I realise that the "diesel god" remark was a bit of a red rag to a bull but even so civility reigns in On Topic .


Well said, I'm pretty new here but I agree, keep it up beat people can disregard what information they wish nobody has to win.


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## Minnewaska (Feb 21, 2010)

Marine engines operate differently than other applications. Even when using a similar block. If specd to your sailboat properly, you should expect hull speed in calm water by running it somewhere in the range of 70-80% of Max rpm. If you have a huge motor for your boat, which space often prohibits, you might get hull speed at a lower rpm. Most wouldn't want to waste the space, nor the weight.

You can always choose to run slower. The issue is, unlike most other applications, your motor will need to run across the spectrum of rpms (docking, slow harbor transit, or long haul motoring), but it's always in the same gear (prop pitch). 

UP claims to be a god. Doubt it, but couldn't say for sure. I highly suspect most of his experience is non-marine. A guy that I know, who I would say was a diesel God, has been adamant that marine diesels have trade offs, between power curves and prop pitch, but they are designed to work optimally in the upper RPM ranges (ie 60-80%). Let the gods duke it out, but do your research before you take any of this or anyone else's advice on how to care for your diesel and don't try to extrapolate from other industries.


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## RichH (Jul 10, 2000)

Minnewaska said:


> Marine engines operate differently than other applications.


Marine engines are primarily operated at a single constant speed/rpm. You dont push down on the accelerator to 'pass' another boat, or to constantly adjust to speed limits as on a highway, or climb hills, you dont 'shift the gears', etc. Marine engines are principally operated in the exact same manner as industrial diesel 'prime movers' .... constant rpm. Prime movers as well as marine diesels - have 'governors' to (attempt to) keep that constant rpm under varying load demand.

The 'god' was essentially correct in most of his apparently experienced based statements.

;-)


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## asdf38 (Jul 7, 2010)

JimMcGee said:


> Actually I have to wonder how much of this has become "tribal knowledge" repeated on sailing forums that may in fact be incorrect.
> 
> This thread piqued my curiosity so I went and re-read the operator's manual for my diesel engine (25hp Universal).
> 
> ...


For what its worth I double checked my Yanmar 1GM10 manual and it specifically does say that the engine should periodically be run full-out.

I tend to hate doing it (my one-banger is loud and vibrates!), but in recent years I've made a point of it. And it does make me more confident in the engine knowing it can take that.


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## outbound (Dec 3, 2012)

Soooooooo
Have 75 turbo yanmar. It gets run for 15m before leaving and 15m after arriving. It gets run at 2100rpm for ~1/2h as we leave and put the rags up then left in neutral for 5m before shutting down and putting the trannie in reverse. 5-8x per year it gets run continuously for one to five days when the wind dies on passage.
This is very different then a truck or commercial pump but probably like what most of us actually do. 
What can I expect for service life? What can I do to prolong it?


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## JimMcGee (Jun 23, 2005)

asdf38 said:


> For what its worth I double checked my Yanmar 1GM10 manual and it specifically does say that the engine should periodically be run full-out.


Which is a bit different from what my manual says. Different engines different answers. It shouldn't be a surprise that one size doesn't fit all.

RTFM - Read the Friggin' Manual :laugher

I'll grant you they're not exciting reading but definitely worth the time.


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## IStream (Dec 15, 2013)

outbound said:


> Soooooooo
> Have 75 turbo yanmar. It gets run for 15m before leaving and 15m after arriving. It gets run at 2100rpm for ~1/2h as we leave and put the rags up then left in neutral for 5m before shutting down and putting the trannie in reverse. 5-8x per year it gets run continuously for one to five days when the wind dies on passage.
> This is very different then a truck or commercial pump but probably like what most of us actually do.
> What can I expect for service life? What can I do to prolong it?


I think you're doing well with it but probably not running it hard enough. I'd check your manual and change 2100 RPM to whatever is 80% of max or, if you can find the torque curve for your engine, max torque RPM. Diesels really do need to be run pretty hard on a routine basis and periodically as hard as they can to keep the combustion chamber and chamber-exposed components in good shape. In addition to increasing your standard operating RPM, I'd also suggest that you run it at max RPM or close to it for 5-10 minutes every few months to get the exhaust gas temp up. Check your manual to find max RPM for your particular engine and the longest recommended run time there.

One good thing about the max RPM procedure is that it's a pretty good general diagnostic test. There are a number of reasons why you might not be able to make max RPM (prop over-pitch, valve clearance changes, exhaust elbow constriction, fuel filter clogging, misadjustment/slippage of the throttle linkage, etc.) While it can be a process to track down the root cause if you can't make max RPM, the flip side is that if you can, you know that things are generally running well.


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## Morild (Mar 31, 2013)

Just looked in my Volvo Penta MD7B manual today.
It says nothing about running it at specific RPM's.
It did, however state that when sailing, one should start and run the engine for about 15 minutes every 3 hours....
I don't know if the PO's did that. I don't. 
It's 30 years old, and starts when I look at it.
RTFM?


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## Capt Len (Oct 9, 2011)

Just guessing but I bet that 3hr start/run while saiing has to do with cooling the gear box Velvet drives ,for example ,need the input shaft turning to circulate oil thru it's heat ex. If gear is free wheeling it can get hot.


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## UnionPacific (Dec 31, 2013)

Capt Len said:


> Just guessing but I bet that 3hr start/run while saiing has to do with cooling the gear box Velvet drives ,for example ,need the input shaft turning to circulate oil thru it's heat ex. If gear is free wheeling it can get hot.


I am not a gearbox god, but I think the back end of the transmission turns when the shaft is spinning. It should not generate heat at all. If it needed to be started to be cooled, a 45 day passage would be impossible without running out of fuel.


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## Morild (Mar 31, 2013)

Capt Len said:


> Just guessing but I bet that 3hr start/run while saiing has to do with cooling the gear box Velvet drives ,for example ,need the input shaft turning to circulate oil thru it's heat ex. If gear is free wheeling it can get hot.


It's a Volvo 120S drive. Don't think it has anything to do with that


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## UnionPacific (Dec 31, 2013)

outbound said:


> What can I expect for service life? What can I do to prolong it?


install an EGT gauge. 
Learn what normal is, and do not exceed 1200 ever. When you are doing your cool down, wait until the EGT temp is less then 250 before you shut it off. When you see what normal is you will see signs of the engine running badly there before anywhere else. If it is direct injected and an injector frys open the EGT will shoot up very quickly, and you must instantly shut down.
If you have an EGR valve, remove it. Your intake will clog with soot.
The EGR removal is the best thing you can do if you own one with it.


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## Minnewaska (Feb 21, 2010)

RichH said:


> Marine engines are primarily operated at a single constant speed/rpm.


Really? I would say my typical pattern is.... 15 mins of warm up at idle, 5-10 mins at 1,000 +/- rpm to navigate out of the harbor at restricted speed. A few minutes at 1500-1800 to get around inbound traffic at the entrance, then 2000-2200 (3000 max) for another 10 mins to position in the Bay. Longer at high RPM, as needed. Not to mention a couple of mins in reverse, at varying rpms, to get back into the slip.



> You dont push down on the accelerator to 'pass' another boat, or to constantly adjust to speed limits as on a highway, or climb hills, you dont 'shift the gears', etc.


Assuming you're already at hull speed, you may decelerate to deal with conflicts. That's backing off the throttle, with no gear shift.



> Marine engines are principally operated in the exact same manner as industrial diesel 'prime movers' .... constant rpm. Prime movers as well as marine diesels - have 'governors' to (attempt to) keep that constant rpm under varying load demand.


A genset may be a good comparison, but not your auxiliary. Ours, at least, operates at several different RPMs/loads. They're not all universally well matched between engine torque and prop pitch.



> The 'god' was essentially correct in most of his apparently experienced based statements.
> 
> ;-)


To each their own.


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## pikesbayone (Jul 25, 2013)

If I could not use the boat, i tried to run it in gear still tied to the dock. (Not possible in all situations.) Not necessary to get as many rpm's because the effective load of a stationary boat is much greater. Another tip: avoid idling in neutral for extended periods. That is also hard on a diesel.


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## RichH (Jul 10, 2000)

Minnewaska said:


> Really? I would say my typical pattern is.... 15 mins of warm up at idle, 5-10 mins at 1,000 +/- rpm to navigate out of the harbor at restricted speed. A few minutes at 1500-1800 to get around inbound traffic at the entrance, then 2000-2200 (3000 max) for another 10 mins to position in the Bay. Longer at high RPM, as needed. Not to mention a couple of mins in reverse, at varying rpms, to get back into the slip.
> 
> Assuming you're already at hull speed, you may decelerate to deal with conflicts. That's backing off the throttle, with no gear shift.
> 
> ...


Actually, the comment by Union Pacific is probably the most accurate .... monitoring of the exhaust gas temperatures - EGT. 
In 'serious' IC engine applications, additional to the EGT - the temperature 'differences' in the heat exchanger are also monitored.


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## IStream (Dec 15, 2013)

An EGT gauge is nice and I'd definitely install one with a new engine, particularly if it's a common rail design, but it's overkill in Outbound's case. Running at 80% of max RPM or at max torque RPM will pretty much ensure that the EGT is high enough but not too high.


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## albrazzi (Oct 15, 2014)

outbound said:


> Soooooooo
> Have 75 turbo yanmar. It gets run for 15m before leaving and 15m after arriving. It gets run at 2100rpm for ~1/2h as we leave and put the rags up then left in neutral for 5m before shutting down and putting the trannie in reverse. 5-8x per year it gets run continuously for one to five days when the wind dies on passage.
> This is very different then a truck or commercial pump but probably like what most of us actually do.
> What can I expect for service life? What can I do to prolong it?


Change the oil frequently and don't let it overheat plus all the other stuff said in this thread basically.


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## Capt Len (Oct 9, 2011)

'I think the back end of the transmission turns when the shaft is spinning Well duh!! Some gear boxes are the same sort of guts as an automatic car tranny. Try towing one behind the motorhome for a day and put your hand on the box. Probably not enough to start a grass fire but close. A shaft lock or feathering prop solves it. Putting it in gear requires the input shaft (front pump) to be turning .Stopping the engine ,no gear oil pressure, plates/disk release but most of the guts are driven by the tail stock ,creating some heat with no oil flow to dissipate it .Pondering a situation before pulling a soup sandwich out of your pocket usually helps .


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## UnionPacific (Dec 31, 2013)

Capt Len said:


> 'I think the back end of the transmission turns when the shaft is spinning Well duh!! Some gear boxes are the same sort of guts as an automatic car tranny. Try towing one behind the motorhome for a day and put your hand on the box. Probably not enough to start a grass fire but close. A shaft lock or feathering prop solves it. Putting it in gear requires the input shaft (front pump) to be turning .Stopping the engine ,no gear oil pressure, plates/disk release but most of the guts are driven by the tail stock ,creating some heat with no oil flow to dissipate it .Pondering a situation before pulling a soup sandwich out of your pocket usually helps .


This has been discussed at great length elsewhere, and the gearbox experts say it does not hurt it to spin. Its more like a manual transmission, but has way less gears. Autos use planetary gearset, and generate more heat because of the belts. I think in one of the discussions velvet weighed in.


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## SloopJonB (Jun 6, 2011)

saltydog4 said:


> I'm looking at a sailboat with a yanmar that has 3480 hours. Sounds like that is a lot.


It isn't. Middle aged at best.

Stationary "steady state" engines such as agricultural water pumps have seen 40,000 hours - that's right *forty *thousand

A boat engine should do 10K unless it's just used for docking.


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## SloopJonB (Jun 6, 2011)

travlineasy said:


> My dad drove a diesel powered tractor trailer, beat the living hell out of the engine, and the first rebuild was at 350,000 miles and it was only a minor rebuild. I don't know what this translates to in hours, but it's a lot of hours. That was nearly 10 years of daily use and abuse.
> 
> Gary


Average MPH is about 25 so 350K miles is about 14,000 hours.


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## UnionPacific (Dec 31, 2013)

SloopJonB said:


> It isn't. Middle aged at best.
> 
> Stationary "steady state" engines such as agricultural water pumps have see 40,000 hours - that's right *forty *thousand
> 
> A boat engine should do 10K unless it's just used for docking.


With that many hours thou I would want to change the heat exchangers, exhaust elbow, and every hose.... I would do the exchangers and elbow after 3000 hours, and the hoses every 10 years or 3000 hours, just preventative.


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## UnionPacific (Dec 31, 2013)

SloopJonB said:


> Average MPH is about 25 so 350K miles is about 14,000 hours.


and they typically turn at about 1200-1400RPM.


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## RichH (Jul 10, 2000)

UnionPacific said:


> With that many hours thou I would want to change the heat exchangers, exhaust elbow, and every hose.... I would do the exchangers and elbow after 3000 hours, and the hoses every 10 years or 3000 hours, just preventative.


..... including a complete changeout of any 'rubber' fuel hoses. ;-)


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## Minnewaska (Feb 21, 2010)

....... and descale the innards.


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## smurphny (Feb 20, 2009)

The big difference between automotive and industrial engines is that cars and trucks coast, a lot, which makes a comparison difficult. Marine/industrial engines are under torque 100% of the time when in gear. 

Every tech manual has torque curve data which should dictate the target RPM for whatever engine with the correct wheel. Yanmars reach peak efficiency around 2500-2800 RPM which is exactly where I run my 3GM30F and where it obviously likes to run. I do believe that varying the RPM by 100 or so around the target RPM is beneficial to cylinder wall/ring wear over time but running at 2000 or lower on a regular basis invites oil burning and cylinder wall glazing. I've had Yanmars, Kubotas, Cummins, JD, and Detroit diesels in different pieces of industrial equipment and have found these same principles seem to hold true.


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