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Old 04-01-2011, 14:01   #16
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A bit outside the box, but if you have not doen so it could be worthwhile to drain the sump, and then refill with the exact correct amount of oil to make sure your dipstick is the right one.
With a newish engine it could cope with extra oil, but with a little wear it may be causing some smoke.
Regards, Richard.
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Old 04-01-2011, 15:12   #17
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Boy, do do know how to leave a girl feeling flat! I have spent [wasted] 47 years working as a diesel fitter, Ship's engineer, heavy machinery fitter, and all the time looking for that super simple key to blue & white smoke, one of us has alot to learn,regarding engine & injection types any where .
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Old 04-01-2011, 15:46   #18
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Wow, nice attitude!! Sorry, only got 22 years experience working with Diesel engines so I obviously have a lot to learn.

With your huge knowlegde then, you wouldn't aggree that blue smoke is the result of oil burning in most situations?
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Old 04-01-2011, 16:23   #19
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Richard, I have confirmed, by putting in a measured amount of oil, that the dip stick is more or less correct... or damn close. I do, however, run it right up at the top! Also, I wonder if it matters that my engine installation is almost level? Most are at a considerable down rake, and mine is just a few degrees down? Perhaps I should try it with the oil showing only at the bottom line on the stick. I have never done this, as I ALWAYS keep it within 1/4" of the top line.

Another key to the puzzle... A couple of days ago was the first time I had seen the engine making blue smoke, EVEN while under load. The problem, in the past, has been ONLY when revved up to over 1,600 and NO load. I don't often do this, and this is why we have just lived with it. Under load... It only makes faint blue smoke like you'd expect from a 16 year old engine.

Two days ago, when I ran the engine, I forgot that I had stuffed rags in the tight engine box's intake and exhaust hoses, so that the "golden rod" could heat the engine space and prevent freezing. (This was the first time I'd plugged the vents). This lack of air must've made the blue smoke worse during that one run, because today when I opened up the air supply, it went back to the same old thing it has done for years... Namely, it makes a LOT of blue smoke ONLY at high idle, but very little in gear and loaded up, or underway. Low idle is also fine, no smoke @ 1,000 RPM at all.

Since 99% of my engine hours is underway, when it makes only normal amounts of smoke, it could be that it DOES burn oil, but ONLY during the 1% of the time that the engine is high idling to warm it up. I like to run the engine once a week, and figured that a very high idle, like 2,000 RPM, was less damaging in regards to their tendency to carbon up, than a slow idle. This may or may not be correct, but that high idling is really the only time I have her belching smoke. Ideally, I would always run her in gear, but my spot in the marina is very shallow, and this would create a dirt dam behind the boat, and ruin my slip.

I'd still like it to burn clean, EVEN at high idle, but not bad enough to pull the engine and have it rebuilt, at almost five grand! Not if I can put it off.

Mac Boring suggest rebuilding the injectors, as this is way past due. My next thought is to adjust the valves, as they are also due. These may not solve the problem, but it is good preventative maintenance. I may also pull the lift pump to make sure that it is not allowing diesel into the oil sump, in small amounts, too minimal to raise the oil line. (A VERY long shot)

One of those things that make ya go hmmm...

Mark
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Old 04-01-2011, 16:34   #20
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Ah, well if' it's only doing it at high reves then it's more than likely to be oil forcing it's way past the rings under extreme load.

For a relatively old engine, not to much to worry about. A compression test is on the cards when you can get round to it, just don't thrash her and keep an eye on the level.
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Old 04-01-2011, 17:18   #21
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Simonmd, The mystry is that the blue smoke from being revved up goes away almost entirely, when it IS under load. (in gear). The smoking is when it is revved up but NOT under load, and since this represents only 1% of its hours, oil consumption over 100 hours is only about half a pint...
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Old 04-01-2011, 17:42   #22
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Quote:
Originally Posted by Mark Johnson View Post
To clarify some of the above...

I have left the problem alone for so long because it cranks and runs so well, and loaded up, underway, MOST of the smoke goes away, or so it seems. Yesterday... I did try a 2,500 RPM rev in place at my dock, (in gear), and it WAS still smoking... so I figured that underway, this reduced amount of blue smoke MIGHT be further reduced in appearance by being diluted from the wind, coming through the wing tunnel. (It is a Trimaran...)

Unless, with the cavitation created by running hard, "in place", is actually NOT much of a load. If that is the case, I haven't imagined it, and the engine really doesn't smoke under heavy load, while under way.

It only makes "black" smoke if I floor it suddenly to full 3,600 RPM, which I seldom do.

At my 3,000 RPM, cruising speed, I consume about .5 gal/hr, which is normal for this engine.

I did adjust the valves just after 1,000 hours, but now at 2,400, it is due again. I will remember... when turning over the engine without cranking, to close the raw water intake. (Thanks for the reminder)

I am not sure if that obnoxious smell is from blue diesel smoke or blue oil smoke???

My gut feeling is that with this incredibly low oil consumption, almost "0", and perfect cranking / running, it is just not burning oil... nor is it the rings, or valves. Although, I will adjust the valves, as they are due. It sounds like un burn't diesel to me.

#1, I will start by having the injectors rebuilt. #2, Then adjust the valves, #3, then do a compression check. It seems that if the injector timing was off, the cranking, running, and / or full power, would be off too?

I have been told by numerous mechanics, that @ 2,500 hours, my engine is just an adolescent. Nevertheless, if I have to pull the engine, I would "consider" having it rebuilt. I hate to resort to this though, as a rebuild cost $1,000 more than the engine did! (16 years ago)

They don't make these any more. Now it is replaced with the the 3-YM... This is a slightly larger, (better) engine, but would require a lot of modifications to get it to fit. On top of that, if I had that extra couple of HP, I would want one more notch of pitch in my prop, so I could use the extra power. (It is an $800 prop)!

So, even at $4,500 for a total rebuild, it is at least several thousand dollars cheaper than a new engine and prop, and WAY less work to reinstall.

With my current engine being so healthy otherwise, and so young, I hope it won't come to that!

Thanks for the feedback... Mark
The only problem with a rebuilt motor is, it's only as good as the mechanic that did the work.
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Old 04-01-2011, 17:50   #23
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That is not a mystery. what is happening is that you have un-burned fuel from not getting the engine, hot coating the combustion chambers and exhaust ports,and possibly some of the exhaust before the water injection. when you load up the engine it gets hot enough to burn off this fuel that is sticking in the exhaust ports. yrs ago when i had trucks with the Detroit Diesels this was always a problem until you took them out on the highway and ran them hard to seat the rings again, after prolonged city use( 6mnthsto a yr) if you are not loading the engine enough your rings and cylinders will glaze. most all diesels have this problem. diesels don't like not being under load! anyway it took 300 miles hard driving(not beating, just long hard pulls)for one of my trucks to stop smoking blue smoke, and also using oil. (it would use about a 2 quarts in 4000 miles. if you are under propped slightly then your engine is not coming up to full op temp internally(combustion wise) in my humble opinion. i'm just looking back from yrs of dealing with G.M.s. i'll tell you this after that truck went to Baltimore and back we never had an issue with it burning oil or getting wet stack(unburned fuel in exhaust)
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Old 04-01-2011, 17:53   #24
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Before you rebuild injectors etc, I'd do the compression tests first as this won't really cost anything.
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Old 04-01-2011, 18:09   #25
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How long do you run it for at high rev's....
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Old 04-01-2011, 18:15   #26
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Mike D, That was my first try, I changed the thermostat, and using an IR thermostat all over the engine, confirmed that it was in fact at its proper 180 degrees. Logical though. Even after a hard 8 hour run @ 3,000 RPM, If I take it out of gear and idle @ 2,000 RPM, back comes the blue smoke... Some would say: "well don't do that" I know.

Ausaviator... I don't have the gauge, but while the injectors are off, (They're WAY overdue anyway), I should do this. Buying a gauge is no big deal, or is it?

Thanks, Mark
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Old 04-01-2011, 18:19   #27
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Boatman 61... It doesn't matter if it has been after warming up for only 10 minutes, or an hour, the key seems to be the lack of a load that makes it smoke like a chimny... M
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Old 04-01-2011, 18:22   #28
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Mark, If you run the engine under no load, there is the possibility that you have polished the bores to the extent that the rings are not sealing properly.
Have you thought of running in reverse in the slip to prevent siltation build up behind the boat?
If it was my boat, I would run it under full load for a few hours, (although it seems you have done that) and see if the situation improves. If you are under propped then maybe you could do it when securely fastened to a wharf which will load it up a little more providing it does not cavitate.
We try never running our Yanmar unloaded, and when cruising run between 2800 and 3000 rpm where possible with occasional 5 minute bursts up to 3600.
Regards, Richard.
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Old 04-01-2011, 18:27   #29
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I suppose a statement like injector jets oversized through age would be a stupid statement....
I'm a former gas converter/engineer wayyyyyyyy back but often we'd have to solder the jets and redrill to the right size when older cookers/fires etc started supplying more gas than the air regulator could cope with making for a 'lazy' flame with orange feathers and not the clean blue burn...
But shoot.... what do I know... just thought I'd join in the merry go round...
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Old 04-01-2011, 18:55   #30
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Mark:

I have followed this thread for several days and if you carefully read everything that has been said this is what you come to:

1. The injectors are fine. If the engine starts on the first crank, then the compression and injectors are ok. Don't do a compression test. Every one says do one but if the engine starts easily it is a waste of time and money.

2. You say that the only time you see blue smoke is when you run it at high idle out of gear. In this case the engine is not burning much fuel and not creating much internal cylinder pressure. The rings leak a little bit of oil past and it gets burned. You don't run it in this condition much so you don't see the lube oil level drop. Perfectly normal for a 2,400 rpm engine.

With the engine in gear the internal cylinder pressure is high and it seals the rings.

3. When you had the engine room vents blocked you created a partial vacuum when you ran the engine. It was starved for air. Usually this produces black smoke as the injector pump tries to pump more fuel. Are you sure that it was blue. But it could be that on the intake stroke the engine pulled more of a vacuum than normal and sucked a bit more oil into the combustion chamber. Again perfectly normal.

All of the above is perfectly normal except for one other possibility that I haven't heard discussed. The diaphragm on the on engine fuel pump may have a hole in it and is letting a tiny amount of diesel into the crank case. Just enough to compensate for the oil that is being burned. I know you said that the viscosity doesn't change but a quart of diesel instead of oil will be difficult to tell. Pull the pump off and replace the diaphragm. This is a long, long shot, but hey it is easy to check.

Good luck,
David
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