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Old 19-03-2011, 18:56   #31
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Re: Yanmar Engine Compression Test Values

New information from the mechanic that did the first set of tests:
Dry all cylinders 250psi. with aprox. 25 cranks or rotations with a diesel pressure gauge.
Wet
cylinder 4-330
cylinder 3-330
cylinder2-350
cylinder1-340
again with aprox. 25 cranks.
With the long term plans you have for the boat you might consider new rings to be installed.
That way the wear on the inside of the engine can be checked when disassembled.

Does this sound reasonable to everybody? What do you think this indicates? Rings and valves?


Finally we are getting somewhere I believe.

Kent

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Old 19-03-2011, 19:43   #32
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Re: Yanmar Engine Compression Test Values

Kent,

Get a new mechanic..mater of fact..trade him in for a technician. 25 cranks..really? First puff, which indicates cylinder wall taper, is determined by the first two cranks.
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Old 19-03-2011, 20:00   #33
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Re: Yanmar Engine Compression Test Values

Decide if you are committed to the boat. If so...decide whether you need to bribe fleet motorpool operators, or take hostages*. Either way can work, when your goal is to try finding one really good diesel mechanic who won't charge an exhorbitant amount. Or, one good diesel overhaul shop, and ask them for a referral. I'd almost hate to say "find a shop, then drag your engine in to it" but...once you open an engine up, it pays to do it all. Rings, valves, injectors, do it all and be done with it. And also send out an oil sample before you open it. The oil analysis can tell you if the engine has been eating bearing metal, and if it needs bearings, WAY before any mechanical assessment can tell you that.

Or...at 3/4 of the original PSI, it might be running well enough to ignore for htis year, if your primary purpose is just getting clear of the berth and moving on windless days.

It was 240, now it's 350...Heck, this is why I started doing my own mechanical work. At least when I screw up the diagnosis, or the work, I know who to call and ream out. And he always makes good on it.<G>

*Just kidding about the bribery and hostages, wouldn't want the forum staff to think I'm encouraging you to do anything impolite, criminal, immoral, unethical, or otherwise in violation of the forum rules.
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Old 20-03-2011, 09:49   #34
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Re: Yanmar Engine Compression Test Values

Your original post asked for comments about his original statement and report. His story has now changed considerably, so now our comments will certainly also change.

I'm with Chief on this. Get a new mechanic. This guy doesn't have your best interests at heart. He has blown his cover with this new information - he is either incompetent or dishonest. Either way, his findings and conclusions are now suspect.

But still I have questions. Did you run this boat? Did the engine smoke? Was it hard to start when cold?
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Old 20-03-2011, 12:02   #35
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Re: Yanmar Engine Compression Test Values

Yes I did run the boat and there was no noticeable smoking other than the first perhaps 15 seconds. She turns right over and seems to run fine. My surveyor suggested that the blowby is recirculted into the engine intake and therefore burned by the engine the second time around.
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Old 20-03-2011, 13:12   #36
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Re: Yanmar Engine Compression Test Values

Quote:
Originally Posted by kentheighton View Post
My surveyor suggested that the blowby is recirculted into the engine intake and therefore burned by the engine the second time around.
A small amount of oil coming from a crank case breather is normal; aka "blow-by". Routing the crank case breather back into the air intake is also standard procedure with boats. It is easy to check how much is coming out by routing the cc breather to an empty bleach bottle and see how much it collects. A tablespoon over a few hours of engine time wouldn't be excessive.

But, if your surveyor is suggesting that the engine is moving an excessive amount oil through the blow by, you would see visual evidence of this in either smoke, or sheen on the water - probably both, not to mention that the engine would need to have oil added between oil changes. This oil the surveyor talks of has to come from someplace, and that has to be the oil sump. If the engine is 'recirculating' that oil ithrough the crank case breather and then disposing of it during combustion, two things must be true: you will see visual evidence of oil being burned as fuel, or you will see unburned oil in the exhaust.

If its a tiny amount, then it is normal and you would not have visual clues as to a problem.
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Old 21-03-2011, 12:42   #37
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Re: Yanmar Engine Compression Test Values

Compression tests were done with a cold engine.

Kent
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Old 21-03-2011, 13:51   #38
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Re: Yanmar Engine Compression Test Values

Kent, at this point, you are going to have to make your own decisions on how to proceed; there is only so much advice and information you can get from internet forums. None of us have seen the motor, so all we can do is speculate.

Here is what I would do: Hire a Yanmar Factory Authorized tech/mechanic. Ask him to check the valve clearances first (because a lot of this could be just that - valves out of specs), and then a compression test.

What part of the country are you in?
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Old 26-06-2015, 23:38   #39
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Re: Yanmar Engine Compression Test Values

ladies and gentleman, I am perplexed.the mechanic / Tech? maybe backpedaling trying to give you a wet vs dry test. adding a smaller amount of oil and the pressure coming out indicates worn rings. the problem with this test is in a diesel that burns oil for a living , adding oil for a wet test the engine could run on that. (Some diesels have primer cups to put oil to help start) also the squish area is so little that much oil could cause a hydrolock. A safer method is a cylinder leak down test adding compressed air and noting where it's leaking from inake or exhaust valve head gasket or if it comes excessively from the crankcase worn rings.... interested in your final outcome...
always remember to celebrate Rudolph's birthday, diesel that is March 18th
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Old 27-06-2015, 10:35   #40
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Re: Yanmar Engine Compression Test Values

Compressed air is great in a shop, with a compressor and AC power. On a boat, equipped with neither and not having them in his pocket? A good mechanic can still tell a lot by a leakdown test (sometimes done with oil, sometimes kerosene, etc.) as long as they are familiar with the viscosity, how much leakage the engine should have, and how long it take their medicine to trickle down into the engine.


Never trust an alleged mechanic who starts his show by removing his top hat, rolling up his sleeves and saying "Ladies and Gentlemen, wanna see me pull a rabbit out of my hat?!"
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Old 27-06-2015, 12:24   #41
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Re: Yanmar Engine Compression Test Values

Oh shiite, I got sucked into the vortex of someone opening an ancient thread...
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Old 28-06-2015, 17:02   #42
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Re: Yanmar Engine Compression Test Values

I want someone to put the specs to analyse starter motor loading onto the microchip of a multi-meter - be a hell of a lot easier to keep an eye on compression levels than pulling the bloody injectors and using a comp. gauge.
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Old 28-06-2015, 17:12   #43
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Re: Yanmar Engine Compression Test Values

With a Pico diagnostic adapter (basically an oscilloscope) or any other scope and some training, you can monitor the starter, and a whole lot more. Ain't just a cheap chip upgrade though, and it would give most boaters a real headache trying to read it.
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Old 18-11-2015, 10:22   #44
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Re: Yanmar Engine Compression Test Values

I just had my compression tested because the #1 cylinder (rear on my 4JH4E) was not pulling it's weight. #4 tested 240 and #1 tested 150. Sad faces all around because the difference was indicating most likely bad rings. The thought was that salt water got in there and the rings are not expanding.
I'd say thank you! that all the cylinders show the same and keep moving.
I'm now forced to pull the engine and rebuild after just being on the hard for 8 months for rigging and awlgrip and electrical which included having the engine out to replace the cutlass bearing.
Say thank you!
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Old 23-01-2016, 08:27   #45
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Re: Yanmar Engine Compression Test Values

1986 Yanmar 4JH-HTE now without the turbo and intercooler.

Here are the pics. done at about 3,300 hours January 2015.

1- 400
2- 350
3- 360
4- 385

The mechanic had to machine an injector adaptor for this job.
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