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Old 17-11-2005, 09:09   #1
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Is 4000 hrs Too Many??

We are in the process of buying a boat with a Yanmar 4JH2-E with 4000 hours of the meter.

On a cold New England morning it started right up. Although there was a lot of white smoke at first it cleared within a couple of minutes.

During the seatrial it ran and sounded good. The PO is very knowledgeable and reports that the engine burns little or no oil.

Paint and overall appearance of the engine is good and does not look like it has been overheated or neglected.

In other words every thing looks good except the number of hours on the meter.

Should I be concerned??

Thanks for your thoughts,

John
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Old 17-11-2005, 09:16   #2
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Impossible question to answer.

Depends on age of engine and how well it has been maintained. Especially how frequently has the oil been changed?

If you equate it to a commercial vehicle engine which is good for several 100,K miles and assume an average vehicle land speed of 30 mph, then this equates to a commercial vehicle having covered abt 120,000 miles. So there is a chance that the engine is as good as new. But there is also a chance that it is completely worn out. A good way to check is to have the engine and gearbox oil analysed as this will reveal a good deal about the condition of the engine. Your surveyor should be able to put you in touch with a firm able to carry this out.
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Old 17-11-2005, 10:47   #3
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if your really interested

If you really want to get this boat and are willing to pay a little to have a secure knowledge of the engine condition do as the previous reply says and have the oil anilyzed. also consider having the a compression check done.
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Old 17-11-2005, 11:30   #4
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OK I am going to take a different line here.
Forget the oil analysis and forget a compression check. They won't tell you didly squat as to how bad and what area the wear is.
First of all, you need what is called a "Leakdown" test. It's not hard to do and you can even do this yourself. The only drawback is getting the tester. What a leakdown is similar in what it is as an instrument, but does the job in a very different way with far great range of results. A compression test only tells you what pressure you have in a cylinder as you crank the engine over, which is a problem of inaccuracy in itself in just that there. The only way you know if a problem exists is if you have a lower than normal compression and/or a major variance between cylinders. but chances are, you already know this anyway, as the engine has to be rather sick for it to show up in anything meaningful as a result. It is not accurate and it doesn't tell you exactly what is wrong and where.
A leak down instrument is fitted to a cylinder in the exact same way as the compression tester, via a glow plug or injector input hole. Compressed air is then injected into the cyclinder via the instrument and the amount of leakage is recorded. Then a simple listening test can determin where the air is leaking to. Is it going past Inlet or exhaust valve heads, is it going past rings and into sump and so on. The leakdown test will tell you with greater accuracey where a problem may lie way before the engine itself points to it with signs. Plus, if it is just a case of valves needing reseating, it's not as big an issue as a rebuild.
The Oil analysis will not tell you how much wear and what the wear is. It just tells you that there is wear and that the oil possibly needs changing. To have an accurate analysis, you have to have a regular/set interval and on going test and thus history. If the oil has been changed lately, then the test will be a glowing positive report, if the oil is old, then the test is going to be negative.
And finaly, I think the answer is there anyway. It sounds like the engine is OK and about right for it's hrs based on your description. You should expect to see the white smoke. It is unburn't fuel that has gone through the cylinder before enough heat has been produced to ignite the cyclinder. If you see this white smoke continue for sometime and tend to puff out, then chances are, one cylinder is not firing. Many reasons why.
There is one thing I would do. Get the injectors and pump serviced. 4000hrs is way over there service time.
Hope this helps.
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Old 17-11-2005, 14:09   #5
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I do appreciate the info...Thanks

Alan I believe the pump and injectors have been serviced not to long ago but I will check. The PO has kept meticulous records of all that he has done to the boat including the oil changes.

I'm hoping the more effort that has gone into detailed record keeping the more effort that has gone into maintenance.

The survey came back with no major problems and a fairly short list of cosmetic corrections needed, a good start.

Good advise from all,

John
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Old 17-11-2005, 21:50   #6
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John, I have always used the formula of 50mph as opposed to the 30 that Talbot uses, but he may be more accurate. A modern diesel should last a minum of 300,000 mi of service, or 6000 hours. More if it is meticulously maintained, and properly run. (Those are subjective standards) Another test I would suggest is to measure the blow by at the crankcase breather. This will tell you allot about how worn the engine is. I do not know the standard for your particular engine, but you should be able to get that information
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Old 17-11-2005, 22:21   #7
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Short answer: NO.

4000 hours isnít much for a well maintained marine diesel engine.

4K hours would kill a poorly maintained engine.
16K hours would be way up there for a well maintained one, but not a real limit.

I did the same thing: Bought a boat with 4000 hours on the diesel and made out okay: 7 years later the engine is doing just fine, but it gets a lot of Tender Loving Care...As should be for a 27 year old Perkins.

I really believe that lifetime is up to the user: Run it good now and then, change oil and filters and keep it cool and clean.

Quote:
You should expect to see the white smoke. It is sunburnís fuel that has gone through the cylinder before enough heat has been produced to ignite the cylinder. If you see this white smoke continue for sometime and tend to puff out, then chances are, one cylinder is not firing. Many reasons why.
Uh, I thought white smoke was water and black smoke was un-burned fuel.
Blue smoke is oil.

Previous boat had a 4-107 Westerbeke that conked out after 10 years and a few thousand hours.
Did not put a load on the thing all the time, but kept using it for battery charging in "neutral"....Not good.

On present boat I charge the batteries running the diesel in reverse gear while at anchor, or in forward tied to a dock...Never, ever any RPM without a load. They get a hearth-attack that way
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Old 17-11-2005, 22:33   #8
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On a diesel, white is usually unburnt fuel, but not the serious kind. You get black when the engine is severely overfueled, but white is just a matter of cold fire. No big deal. 16000 hrs is amazing, but not inheard of, and yes, maintainance is the real issue. You always get the exceptions, but on the average, an engine with 6000 hrs will be tired. 4000, some would say just broke in
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Old 18-11-2005, 00:00   #9
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Piston Rings Worn Out?

Sound like to me, like it possibly could be worn out piston rings. Something to add, to the maintaince/overhaul checkup?

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Old 18-11-2005, 00:14   #10
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Good point CSY. Thanks Kai Nui, but if I take this a little further, because I can see where these terms could be confusing to some.
Firstly Black smoke. This has often been called "unburn't" fuel. Mmmm, kinda true but technically incorrect. Black smoke is fuel that has been burn't with not enough oxygen present. Firstly, we need to think about Chemistery here. The fuel particles, or little droplets of Hydrocarbons, are chemicaly reacting and resulting in rapid oxidation, producing tremedouse heat and expansion of gases in the way that we can harness this power and use it to move the Piston in the cylinder. In a proper and correct burn, the imense pressure, heat and oxygen will cause all the particles to oxidise and most all the carbon is burnt away. Not enough oxygen results in the particles not burning efficiently and compleatly, leaving carbon particles. The carbon is black of course and we see it being blown out the back of the exhaust as black smoke.

White smoke is pure fuel and is more technically correct to say it is "unburnt" fuel. The Deisel engine works by producing an enormouse amount of pressure in the cylinder. The Piston is forced up and compresses the Air in the cylinder. The pressure is so immense, that the Air reaches a very very high temperature and just as the Piston gets to the top of the cylinder, the fuel is sprayed into the cylinder under immense pressure through a very small hole. This produces a very fine mist of Deisel fuel that rapidly heats and explodes into flame. But if the pressure of the cylinder is down, maybe due to valve leaks or cylinder wear, the temperature is still hot enough to vapourise the Mist of Deisel, but not quite hot enough to cause it to combust. So we see a "white smoke" of Deisel vapour being ejected out the exhaust.

Blue smoke is engine lubrication oil being burned in the cylinder along with the fuel. I am not sure why the blue ecxactly, it maybe due to additives put into lubrication oil to do the job and Lubrication Oil has a much higher ignition point than fuel oil, so tends not to burn very well at all.

Water vapour in exhaust is much harder to diagnose. Epsecially ina water cooled exhaust system. Usually water int he exhaust will mean it is getting into the cylinders and the smallest drop of water robs the cylinder of much needed heat to start the combustion. So chances are, a water problem will be seen as an engine being difficult to start, an engine that runs ruffly on a couple of cylinders or an engine not wanting to start at all. Because the gap in the cylinder is so small when the piston is hard up, very little water in the cylinder can result in the piston locking of hydraulicing at the top of it's compression stroke. I have seen this happen and the result can be from no damage to the worst I have seen, the block being cracked and the conrod being bent.

PLEASE NOTE: any of these smoke signs coming from an exhaust may not always mean that you have X problem. There are many other tests that need to be done to determin just what exactly the problem maybe. But smoke does show that some problem, maybe minor, maybe seriuose, is most likely present.
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Old 18-11-2005, 13:22   #11
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Thumbs up This one has 7000 hours

And still running strong.

Maintenance, Maintenance, Maintenance, Maintenance, that is the key word. If the previous owner kept it in good shape then it'll probably be safe to say it'll go a while longer. The main thing it to take care of ANY little thing that shows up, when it shows up. But have a good diesel mechanic check it out during the sea trial or before the survey.

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Old 18-11-2005, 21:13   #12
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Nice marine engine you got there, delmarrey. I myself have always taken great pride in all my engines. My own including my customers. And since I am a mechanic. I can say that.

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Old 20-11-2005, 10:29   #13
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Good advice, I would also have the valves adjsutment checked,
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