How to destroy a new $20K diesel

[Zingaro69]

Originally Posted by Terra Nova

This is how it should be plumbed.

Help me understand. Water exits my exhaust in burps and spray. Is the entire vertical section here full of water? Is it half full with six inch pockets of all water then all exhaust as it seems when the exhaust exits the stern? What about the down slope horizontal section? Why doesn't the water flatten out on the bottom of the hose and drain steadily with exhaust in the top half of the hose? Why the surges of water and exhaust? How much water is actually in the hose? Watching the stern it appears to be mostly gas and no more than a third water.

S/V Thin Wolf

[Terra Nova]

Originally Posted by Zingaro69

...4. My best guess at this point is a bad gasket between elbow and the manifold...
The gasket looked fine when it came out...

The gasket looked fine, but your best guess is a bad gasket. WHY? Because it's cheap? I'm all for hoping for the best and dealing with rest, but this kind of trouble shooting technique won't likely get you far.

That long horizontal run probably remains 1/2-full of water (or more), while you're running, then dumps all that water back into the muffler and up its inlet hose when you shut it off.

Look at the drawing. If your system isn't plumbed close to that, expect trouble.

[jongleur]

As Dr. Dean Edell used to say, "When you
hear hoofbeats, expect horses, not zebras."

Have you contacted Vetus? They deal with
this stuff all the time.

Wet exhaust with exceptionally long runs/
lack of good angles seems most likely.

[Marqus]

Reading the thread, the OP has stated several times he is keen to understand how the salt build-up occurred without any cylinder being flooded.

The "too long exhaust line" explanation does not seem to offer an explanation for that (unless I'm missing something). Would anyone convinced of the bad/long exhaust line answer care to explain the salt build-up with zero flooding?

[Zingaro69]

Exactly. Thank you. It is not that I am not listening I am but I can't get my head around that much salt without flooded cylinders. If my exhaust is backing up where is the water going?

S/V Thin Wolf

[Captain Bill]

Perhaps the problem stems from a leaky exhaust valve. Pressure in an exhaust system is not constant but comes in pulses. You would think in a 4 cylinder engine at least one cylinder would be on the exhaust stroke, but perhaps timing results in pressure waves and for a short time there is little or no positive pressure in the manifold. If one had a bad exhaust valve on a cylinder that was on it's intake stroke it might create a slight negative pressure in the manifold. Probably not enough to suck in a big slug of seawater but something more like a mist from the elbow. Given that the Manifold is pretty hot this mist would flash to steam pretty quickly and the salt would be deposited in the manifold, or at least some of it would. I would think that there would be little chance of it getting very far inside the manifold but be mostly deposited near the elbow. Perhaps the valve issue was the cause of the problem, not the result. I just don't know how one would test this theory.

[jkishel]

It appears that the hydraulic capacity of the exhaust piping and/or muffler is inadequate to provide for complete, timely removal of the raw coolant water. The capacity is not so limited that water actually backs up in volumes large enough to fill the cylinder (imagine a severely constricted or entirely blocked system), but there's enough water remaining in the exhaust piping between the mixing elbow and the muffler that some (doesn't have to be much) occasionally gets back to the number four cylinder either during operation (maybe only during rough seas, on port tack, whatever) or maybe only just after the engine is turned off (my guess), to get close enough to number four to boil. The salt in that bit of water precipitates on to the metal and accumulates over time until the exhaust passage is blocked. The resulting steam rejoins the exhaust stream.

The hydraulic capacity can be increased by using larger diameter hose, reducing hose length, increasing muffler size and/or reducing the number and severity of hose bends. It is especially important that the run between the mixing elbow and the muffler be as short as possible while providing adequate vertical distance between the mixing elbow and the muffler (the point of the extended riser mixing elbow mentioned in a previous post).

[hpeer]

ZING,

FIRST, I'm no expert, but we bought a boat that had a somewhat similar issue and set up. But not near as sever.

I understand the difficulties you are facing with the exhaust run having a 44' cc ourselves.

I strongly disagree With Terra Novas attitude that it MUST be done his way or you are condemned. What is shown is ONE way of dealing with the issue, not the ONLY way. Are we to condem all cc's because they're don't alloew the PERFECT exhaust set up? I think not. It strikes me too much of what you are hearing here is religion, not engineering.

That said.......

Of all the answers and suggestions as to what happened I like your 4 the best, or maybe hate it the least. I don't see a better explanation, and those who have dismissed it have not provided a better answer that fits your observed facts.

That said, I would consider regigging your exhaust to improve it if possible.

What we did (now remember, I was starting with an IDIOTIC installation) was
....Yanmar 4JH
... Move the muffler out of the bilge ( not applicable to you)
... Make/install a custom exhaust riser to get above water level
... Install muffler in engine room close to engine .. This where I could make it fit
... Bigger exhaust hose to meet Yanmar specs
... Vetus non return valve in exhaust hose, to keep water from overwhelming muffler
... Vetus gooseneck, to shorten water column even more
... Relocate the exhaust thruhull so it was lower thus with less back pressure.
... Flapper on exhaust, to limit water that can get in during a following sea, pretty ineffective in this installation, IMHO.

That was a complete and expensive rebuild of the exhaust system. BTW, two professional surveyors had inspected the boat and not said a word about the idiotic design. I saw it, but underestimated the time and effort involved.

I hope this is of some help.

Maybe. All you can do is replace the gasket, make what improvements seem reasonable, and pray for the best.

Good luck.

[jongleur]

I'm under the impression that when some
diesels come to a stop, their last gasp
sometimes aspirates the exhaust backwards
for an instant. I've heard that some diesels
may even diesel backward for a bit.

True?

[hellosailor]

It must be Monday somewhere, sometime, soon. I'd be curious to know if the OP could learn anything from Yanmar or Vetus. the one or the other surely has come across this before, whether they'll admit it or not.

[a64pilot]

KP 44 isn't a real rare boat I don't think, it was one I was considering.
I believe they have an owners group, how about asking about your exhaust routing over there?


Sent from my iPad using Cruisers Sailing Forum

[hpeer]

Now THATS a great idea!

[Marqus]

Originally Posted by jkishel

It appears that the hydraulic capacity of the exhaust piping and/or muffler is inadequate to provide for complete, timely removal of the raw coolant water. The capacity is not so limited that water actually backs up in volumes large enough to fill the cylinder (imagine a severely constricted or entirely blocked system), but there's enough water remaining in the exhaust piping between the mixing elbow and the muffler that some (doesn't have to be much) occasionally gets back to the number four cylinder either during operation (maybe only during rough seas, on port tack, whatever) or maybe only just after the engine is turned off (my guess), to get close enough to number four to boil. The salt in that bit of water precipitates on to the metal and accumulates over time until the exhaust passage is blocked. The resulting steam rejoins the exhaust stream.

Jkishel, this explanation has merit since you back it up with good detail.

Observations re this mode:
1) The salt is only deposited while the engine is running
..
2) With the engine running, it must be a repeated coincidence that the water splashes back up only to the same spot in the exhaust manifold, and not past that spot, given the boat's motion in a seaway. But is is possible.
..
3) With the engine running, how can a complete blockage be formed while exhaust pressure is continually pushing exhaust air out of the cylinders?
Or, alternatively, if a blockage is in effect being formed, will the running engine not splutter and die if it cannot easily evacuate exhaust gases?
..
OP, did you notice any loss of power or change in behaviour during the last use of the engine?

[jkishel]

1) Not necessarily occurring only while engine is running, could be happening just after engine is shut off, manifold is still hot, raw water is still in the vicinity of the mixing elbow, water boils, salt is left behind.

2) Not a coincidence, number 4 is closest to the mixing elbow, all the water boils off there, none reaches 3, 2 or 1.

3) As salt gradually accumulates, engine performance would gradually decline, but probably not noticeably for a while, maybe a long while.

The precise mechanism of salt deposition is interesting, but unimportant. What is important is that there is too much raw coolant water in the vicinity of the exhaust manifold because the exhaust system is not removing it as needed. The evidence is the salt that is left behind after the water is boiled in the manifold. As long as the anti-siphon on the raw water side is high enough and working, there is simply no other way for salt to get there. One or more of the exhaust system components is blocked, too small or configured to prevent water from being properly removed or to prevent back flow into the engine.

Specifically:

Outlet at stern should be above sea level.

Exhaust hose or gooseneck should rise at least 350mm above sea level.

Waterlock muffler should be directly in line fore and aft with the mixing elbow and be as close to possible and at least 250mm below the mixing elbow (bottom of elbow to water surface inside the muffler). Should provide a high rise mixing elbow if necessary to get the vertical separation.

Waterlock muffler should not be installed sideways across the boat.

Waterlock muffler must be working properly.

Hoses should be in good condition and proper diameter for the engine size.

The closer one can get to meeting these criteria the more likely the exhaust system capacity will be adequate.

[Marqus]

Originally Posted by jkishel

1) Not necessarily occurring only while engine is running, could be happening just after engine is shut off, manifold is still hot, raw water is still in the vicinity of the mixing elbow, water boils, salt is left behind.

2) Not a coincidence, number 4 is closest to the mixing elbow, all the water boils off there, none reaches 3, 2 or 1.

3) As salt gradually accumulates, engine performance would gradually decline, but probably not noticeably for a while, maybe a long while.

All good points, the best I've noticed in this thread.

Given that the OP said "*The salt is packed solid in #4 exhaust port all the way back to the exhaust elbow.*, I would have thought the engine's running would have HAD to show noticeable effects of this blockage. But I don't see a better explanation than the one you offer.