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Old 08-01-2015, 08:10   #106
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Re: How to destroy a new $20K diesel

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Originally Posted by Wotname View Post
No, sorry, it doesn't make sense.
The water vapour will not contain any salt.

Water will become 100% water vapour once it reaches 100 C (or higher). I'm not sure when NaCl will become salt vapour but it many many times higher than that.

However, there will be plenty of salt left behind wherevever the water becomes vapour
That is where I was going, how does water, even small amounts, get drawn back up to the engine?

Perhaps "mist" would be a better word than vapor?

Is it possible to get a sufficient negative pressure in #4 relative to the exhaust to cause water to be drawn back to the cylinder. Either just as the engine shuts down, or later as it sits.

I had a very slightly similar situation with a 600hr JH4 in our big boat. A valve was stuck open with no other signs of damage but very slight signs of rust.

So I don't think this guy is alone. Also wen both have cc's. We had really bad exhaust install that has been redone, described above.
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Old 08-01-2015, 12:30   #107
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Re: How to destroy a new $20K diesel

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Originally Posted by hpeer View Post
That is where I was going, how does water, even small amounts, get drawn back up to the engine?

Perhaps "mist" would be a better word than vapor?

Is it possible to get a sufficient negative pressure in #4 relative to the exhaust to cause water to be drawn back to the cylinder. Either just as the engine shuts down, or later as it sits.

I had a very slightly similar situation with a 600hr JH4 in our big boat. A valve was stuck open with no other signs of damage but very slight signs of rust.

So I don't think this guy is alone. Also wen both have cc's. We had really bad exhaust install that has been redone, described above.
Yes, mist would leave salt behind as it dried.
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Old 08-01-2015, 12:48   #108
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Re: How to destroy a new $20K diesel

So....I think we are all overthinking this..... the engine was apparently fine when being used. Then it was stored for a long time. Maybe the solution is simply to disconnect the exhaust hose if storing it and taping over the outlet!
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Old 08-01-2015, 12:51   #109
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Re: How to destroy a new $20K diesel

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...
Flushing the engine should never be done with a hose. The raw water pump inlet hose should be inserted into a bucket of water with the hose keeping the bucket filled only. Then the pump will draw water from the bucket.
...
I just learned the other day another reason for using this procedure when flushing engine. Am on the hard, and I had a water hose run into the through hull, and had my wife crank open the water hose valve just as engine started. Ran for a short while, then water stopped coming out of exhaust. Shut engine down. Was scratching head wondering WTF when all of a sudden bilge pump came on pumping water out side of boat. Checked in engine room and found my Groco water strainer bowl (clear plastic) had blow apart. By the way that plastic bowl is about $55 from Defender, and is delaying my launch at least a week waiting for part.

I had used this procedure in past with no problem, was just careful to turn water off if engine was not running. Time to change procedure I guess.
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Old 08-01-2015, 12:58   #110
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Re: How to destroy a new $20K diesel

I've done it with no issue just taking the top off the raw water strainer and putting the hose in. excess water flows out the top of the strainer. You need your garboard plug open or bilge pump on though!
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Old 09-01-2015, 22:50   #111
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Re: How to destroy a new $20K diesel

@Terra Nova A couple of measurements and a small amount of guessing I put the waterline at the top of the engine. With the exhaust well above waterline.

@hpeer what you are seeing is a vestus anti siphon between the heat exchanger and the exhaust elbow.

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Old 09-01-2015, 22:55   #112
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Re: How to destroy a new $20K diesel

I have read several articles on Tony's Tips but no ah ha moments. They do have much higher exhaust risers which I may consider fabricating if I can't find any other causes.

S/V Thin Wolf
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Old 09-01-2015, 23:51   #113
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Re: How to destroy a new $20K diesel

The diesel started getting put back together today. I've taken a lot of pictures so you can see the entire setup and visualize it better.

Raw water leaves the heat exchanger passes through the anti siphon before entering the exhaust elbow (plus feeds water to the drip less shafts seal). Exhaust/water mix exits straight down under the engine to the water lock muffler located forward and below the engine. What you couldn't see in the previous pictures is the exhaust splits into one and three inch hoses. (I have dual exhaust. The engine failed the first back pressure test on initial inspection but passed easily with this configuration. Water and exhaust exit the transom through both hoses). The exhaust exits the engine room and loops inside my cockpit locker and downward before traveling down the side of the hull to the transom where I have a gate valve I can close to following seas.
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Old 10-01-2015, 08:18   #114
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Re: How to destroy a new $20K diesel

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Originally Posted by Zingaro69 View Post
...What you couldn't see in the previous pictures is the exhaust splits into one and three inch hoses. (I have dual exhaust. The engine failed the first back pressure test on initial inspection but passed easily with this configuration...
What genius did this? It appears that the exhaust hose drops from ~4" to 3" (+ a 1") here. Big error. This could be another of your problems.
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Old 10-01-2015, 09:18   #115
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Re: How to destroy a new $20K diesel

I'm not a math genius but if my arithmetic is right a 4" hose will flow a lot more volume than a 3" plus a 1". But more than that it appears that the split is in the up line after the muffler. The water has to be lifted by exhaust pressure and volume. This looks like a way to really confuse the issue to me.

I haven't seen the specific measurements addressed yet. I would make sure that the system meets the requirements of: exhaust manifold or goose neck distance above waterline, hight of the exhaust manifold or goose neck above the water lift muffler, then as short a distance as possible to the highest position of the last hose with a gradual down hill run to the exit from the hull.
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Old 10-01-2015, 10:42   #116
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Re: How to destroy a new $20K diesel

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Once my engine is running again can I adequately test this theory by running the engine, shutting it down and removing the input hose from the muffler to see how much water is there
Commercial water locks (vetus) have a capacity rating, you should check that the capacity is not exceeded by measuring the water left in the water lock after shut down. You should also check that the line to the anti siphon does discharge into the water lock and be accounted for.
I would consider a gooseneck as close as possible from the water lock and installed at a suitable high.
Any seawater that remain in an exhaust line and work like a piston when the boat move will push salt laden air back toward an engine. At the outlet end of the gooseneck I would install a suitable plastic ball valve to prevent movement of salt laden air toward the engine and try not to forget to open it when I run the engine.
A riser on a main engine will run red hot. Mine does and to minimise fire risk and heat the riser is inside a sealed asbestos sleeves like most water cooled heat exchanger manifold are.
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Old 10-01-2015, 11:13   #117
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Re: How to destroy a new $20K diesel

Oh, my. Why would you set it up the same way
again? Are you getting professional help?

Here's an illustration showing the cross section/
handling capacity of a 3 inch + 1 inch hose vs
a 4 inch hose. Why would you transition from
4 to 3+1? That would also mean that if either of
the 3+1 hoses were full of water, the exhaust
would just go out the clear one and not push water
out the other. That alone would allow a huge
amount of static water to flow back upon shutoff.

I sure cannot follow the logic in your set-up.
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Old 10-01-2015, 12:23   #118
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Re: How to destroy a new $20K diesel

There should only be one exhaust hose. It must be of adequate size. Exhaust hose is a lot cheaper than engine repairs. Interesting that back pressure was excessive with the 3 inch hose only. The parallel 1 inch hose actually adds very little capacity to the system, maybe none at all if it is full of water.
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Old 10-01-2015, 12:26   #119
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Re: How to destroy a new $20K diesel

"Dual exhausts"! Just laughing.
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Old 10-01-2015, 13:49   #120
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Re: How to destroy a new $20K diesel

Hi there, I think that the OP is describing his new exhaust installation s a water lift with water separator. This method is recommended for CCockpit installations or other long runs. The exhaust is first cooled in the waterlift/separator then continues on its merry way without any water in it. It is now basically a dry stack hence smaller diameter. The water outlet of course can be much smaller. This is a newer style install but reduces back pressure problems. Google Halyard water separators. Again, NA Dave Gerr recommends them in his book, "Boat Mechanical Systems"

Greg
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