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Old 10-02-2010, 12:31   #31
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I'm not sure the RPM is the issue, but the load on a diesel during it's life. If the piston rings are not under a load they tend to polish the cylinders inturn causing even less compression. But a light amount of polishing can be corrected by putting the motor back to work, I've been told.

In Tspringers motor I suspect he had a small amout of water sitting in the #1 cyl. for 6 mo. and upon start up either broke the piston rings or scored the cylinder. We will not know until it comes apart.
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Old 10-02-2010, 13:41   #32
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The one HUGE thing missing from this thread is age failure time from lack of use. You can run just about any diesel engine all day long every day without fail for years.......just as sigma sailor points out about ships go thousands of hours. I have seen more engine failure (propulsion and generators) with low hours and a years of age. The number one worst thing is to sit for months or years without being laid up properly!!
When I was working as a shipboard engineer we kept a strict schedule of starting and loading the backup engines weekly, the generator and air compressor engines were started run so they would work when needed.
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Old 10-02-2010, 15:03   #33
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Yanmar hours

I have twin 1996 2GM20F Yanmar diesels with approximately 2100 hours each.

Oil and filters are changed regularly. Surveyor of present boat and surveyor of two boats I looked at prior both feel 10,000 hours is reasonable for Yanmars with diligent maintenance.

Marshall
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Old 10-02-2010, 15:52   #34
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I just rebuilt my 1978 YSM8R (single horizontal cylinder 8hp) for the first time. I can't tell you how many hours were on it before the rebuild. The reason for the rebuild was a burned exhaust valve causing low compression and hard starting and lots of soot in the exhaust water. I did replace the mixing elbow a few years back because it was almost corroded shut. For a motor that is so small it has held up very well. It smaller than most of the generators you guys use on the big boats.

I also worked the far north for a couple of winters and we NEVER shut of any piece of diesel equipment outdoors after about October because the fuel would gel and then you would almost never get it to start again. Many of the road dozers had fuel lines with extra coils running inside old coffee cans next to the exhaust manifolds to help keep the fuel liquid. Kind of like the opposite of "cold cans" racers used to use back in the old days to keep gasoline cooler.............m
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Old 10-02-2010, 16:09   #35
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Quote:
Originally Posted by JustCatamarans View Post
We deal with a lot of ex-charter cats that have the $jh and 3Jh series.
It is not uncommon to see them at 5000-7000 hrs and still going, bearing in mind that the engines are abused in the charter marker, whether running under max load, cold to full rpm running, and idling.
In my opinion they are the best kae of diesels, the parts are considerably cheaper than Volvo and easier to work on
I'm looking at purchasing a former charter catamaran with 38hp 3jh's, they have 6,700 hours each, they run like new, 2004 model year boat and engines. I will be budgeting for rebuilds if I do make an offer on it but am curious to see how long they will last, I'm almost tempted to to run them until they die with rebuild kits and a machine shop on standby. If they do last to 10,000 hours, 3,300 hours is a lot of time for me, probably 7-10 years of use.
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Old 10-02-2010, 23:31   #36
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3gmc 22 1/2 hp. 25 years...no hour meter...approx 2,500+ hrs
replaced starter and exhaust system all else original including
mixing elbow(checked and cleaned several times, didn't need it)
repainted few years ago, looks new. Over the years I have talked to Mack Boring and my mech and (in addition to normal maint.)
I ask them what can I do to preserve motor...they always answer
don't baby it, run it hard...so far so good!
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Old 11-02-2010, 00:20   #37
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Off topic I do have some commercial busses with 765k miles (30k hours on DD's) that are weak but do run ok for now, they are not worth rebuilding.
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Old 11-02-2010, 05:55   #38
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That high rpm vs low rpm is no brainer to me. Along with higher loads caused by centrifugal force, it simply turns more rpms causing more wear. Net times piston travels up and down in same time is more, how simple.
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Old 11-02-2010, 07:39   #39
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Made an offer on a boat with a 3GM30F engine. Before I move the boat to the Caribbean, what types of preventive maintenance should I have done? I would rather do more than necessary than less. Current hours are 750.
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Old 11-02-2010, 09:40   #40
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I have a 1995 4JH2te turbo 65hp. 1860 hours on the meter. Propulsion time only. No problems observed yet. I am however about to clean up the engine space and like Terry merely want to have a shipshape compartment. I procede with caution and determination. I have only had the boat since last August but the logs are excellent. I will continue that practice.

Regarding engine life, the posts here are all good. Keep the fluids changed, run the engine loaded at a substantial fraction of max rpm at 100% of normal operating temperature frequently. Keep your fuel clean. Make a practice of knowing what is going on down in that space on a detailed basis.

This a good thing guys! Use the boat more and fool around in the engine compartment more! Cool.
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Old 11-02-2010, 20:36   #41
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Quote:
Originally Posted by forsailbyowner View Post
That high rpm vs low rpm is no brainer to me. Along with higher loads caused by centrifugal force, it simply turns more rpms causing more wear. Net times piston travels up and down in same time is more, how simple.
FYI- Diesel engine damage due to misapplication or misuse of generating set

Quote:
Diesel engines can suffer damage as a result of misapplication or misuse - namely internal glazing (occasionally referred to as bore glazing or piling) and carbon buildup. This is a common problem in generator sets caused by failure to follow application and operating guidelines. Ideally, diesel engines should be run at least 60-75% of their maximum rated load. Short periods of low load running are permissible providing the set is brought up to full load, or close to full load on a regular basis.
Internal glazing and carbon buildup is due to prolonged periods of running at low speeds and/or low loads. Such conditions may occur when an engine is left idling as a 'standby' generating unit, ready to run up when needed, (misuse); if the engine powering the set is over-powered (misapplication) for the load applied to it, causing the diesel unit to be under-loaded, or as is very often the case, when sets are started and run off load as a test (misuse).
Running an engine under low loads causes low cylinder pressures and consequent poor piston ring sealing since this relies on the gas pressure to force them against the oil film on the bores to form the seal. Low cylinder pressures causes poor combustion and resultant low combustion pressures and temperatures.
This poor combustion leads to soot formation and unburnt fuel residues which clogs and gums piston rings, which causes a further drop in sealing efficiency and exacerbates the initial low pressure. Glazing occurs when hot combustion gases blow past the now poorly-sealing piston rings, causing the lubricating oil on the cylinder walls to 'flash burn', creating an enamel-like glaze which smooths the bore and removes the effect of the intricate pattern of honing marks machined into the bore surface which are there to hold oil and return it to the crankcase via the scraper ring................
Diesel generator - Wikipedia, the free encyclopedia

Diesel Talk Forums - Glazing of cylinders

Why do the cylinder walls glaze on a diesel when... - JustAnswer

Quote:
Yanmar's workshop manual suggests that after two hours of low-speed operation their engines should be revved in neutral to maximum speed in about five bursts, to clear out carbon deposits. They also suggest that periodical operation under full power while underway will benefit the engine, for similar reasons.
Bore glazing

Cost Effective Maintenance - Diesel Smoke tells YOU a Story...
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Old 12-02-2010, 00:40   #42
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Great post. I buy it. The only reason my (off topic) Detroit D's have gone 765k miles (in a bus) is because they are run 50% + 90% of the time. When they are ideling for an hour, bad news, smoke for a few min, poor performance.

I put duralube in my planes engine (against everyones advice, gas 100LL) 5 years ago, rebuild times were 2K hours, few on record ever made it to that, I'm at 2400hr.

I am going to use it in my boat and go against everyones recomendations.
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Old 12-02-2010, 08:03   #43
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1984/5 Yanmar 3GM(F) 22HP currently 1005 hrs

Starts well (no pre-heater on GM's) summer or winter, was abused and by previous owner, last year replaced exhaust elbow and riser and checked heat exchanger to cure overheat under load at plus 2,000 rpm's. Also replaced primary (now Racor 500 series) and secondary (still Yanmar original) fuel filter assemblies plus drained and physically cleaned interior of fuel tank to cure repetitive engine stoppage in rough seas. This is a great little engine.....
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Old 12-02-2010, 09:51   #44
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Two 1994 3GM30's with 3200 and 3400 hours respectively; I suspect that they should be good for double that. They run perfectly, have great compression and do not burn oil between changes.

Brad
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Old 12-02-2010, 15:16   #45
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3JH propped to max at 3600 rpm. Usually run around 3000 rpm. 1000 hours, runs like new. Regards, Richard.
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