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Old 04-06-2009, 21:33   #1
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Raw Water in Cylinders Via Exhaust?

Hey fellas,

Not sure if the problem I have here is a design problem, a ME problem, a fault in the system or a combination.

I am in the process of bringing back to life a 5 year dormant diesel in my "new" old sailboat.

I found that there was water damage to the head and a couple of cylinders. This engine had only 52 hours on it in the logs and I believe this to be true.

The block and head were replaced after 2500 hours because it had water damage inside. The P/O never did find out what the problem was, just replaced the bad stuff.

Is there some reason I can't move the place where the raw hot seawater enters the exhaust a little further away from the exhaust port than the 6 inches it is right now?
I know the raw water keeps the exhaust hose cool but if I extended the metal/cast iron ehaust manifold to something else for a foot or two and wrapped it with exhaust tape to keep the heat down,..????

Just wondering if this might have been a design flaw since the old engine died of this problem and the "low hour" replacement is suffering from the same thing.
I think the vetus water muffler thing should do something for this but its 4 feet down the pipe from the engine... whats keeping the water from backflowing at the exhaust???

My engine is an older Vetus, P4.25. it's a Peugeot car diesel engine that is marinized with an AMC head and a cooler bolted to it.

The only way raw water could get into this engine is either via the oil cooler (an external tube mount that I pressure tested to be good) OR raw water is backing up in the exhaust and entering thru the exhaust ports.
There is no other link between the two seperate systems.

This system uses the standard plastic Vetus exhaust "muffler" that is a kind of a snorkel looking design but the exhaust definately goes uphill abit over 10 feet, then levels off and then goes UP another foot and out the stern ( a bad design???)

Since I found damage after only 52 hours of running,(although sitting for years with salt water in the cylinder/head, if it did get in last time running added to the damage)
I am leaning towards the thought that somehow the raw sea water is getting back into the cylinders.

The raw water exits the exhaust at the Y of the exhaust very close to the exhaust ports.
Is there a flapper valve or something that should stop the water from going the wrong way or is this type of system totally depending on the exhaust pressure to keep it going the right way.

The reason I ask is that I have been attempting to get this engine running all week and I hooked a garden hose up to the intake line that is normally not pressurized, it normally receives water @ a thru hull and a pump on the engine sends the raw water thru the system.

Being abit new to this type of cooling, I had the hose ON for a bit when I was playing with the engine trying to get it running and after a wack of failed attempts.
I ended up pulling the head because of low compression and also removing the oil since I needed to drop the pan and pull the pistons to get rings unstuck.

When I drained the oil I found almost 2 quarts of FRESH water in the oil.

There was NO coolant in it, just plain water, not salt water, this water MUST have come from the hose I had hooked up to the thru hull line.

This may be a seperate issue however it might be the same problem.

Anyway, as I said earlier,... is there some reason I can't move the place where the raw hot seawater enters the exhaust a little further away than the 6 inches it is right now?
I know the raw water keeps the exhaust hose cool but if I extended the metal/cast iron ehaust manifold with something else for a foot or two and wrapped it with exhaust tape to keep the heat down,..???

I get the head back tomorrow and plan to put it all back together but really I don't wanna end up with the same problem...

Any help with this would be appreciated.

Thanks much....kev
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Old 04-06-2009, 22:05   #2
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You have 11 feet of lift from the engine?

Imagine the water working its way uphill while the engine is running.

Imagine all the water in that hose.

Then shut off the engine and it runs down hill...to the engine

Give us more detail and pictures if you can and we will figger it out.
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Old 05-06-2009, 00:26   #3
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Also, do you have a vented loop on the connection from the engine to exhaust elbow? If not you can siphon water into the engine past the cooling pump impeller. But it sure sounds just like simple backflooding from all the exhaust hose into the engine. 11' of lift means a LOT of hose.

The silencer must be well below the engine AND it must be big enough to contain the volume of water that is in the exhaust hose when the engine is turned off.

A conservative estimate is about 1/2 the volume of the hose may be filled with water at any time.
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Old 05-06-2009, 00:50   #4
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Vented loops are a recipe for disaster. They work fine till the vent sticks closed and doesn't break the syphon, btdt. Instead of the ball valve at the top of the vented loop, put in a hose barb. Attach a small diameter hose to the barb line run it out high on the hull with a loop as high in the hull as you can get it. Might even want to vent it into the cockpit so you can check that there is water flow in the exhaust. It doesn't flow out at a great btw, more of adrip unless there is a real head on after the vent.

One reason to run the engine up to cruising rpm and then shut down immediately when your pau is to blow as much water out of the exhaust as possible.
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Old 05-06-2009, 04:40   #5
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I have no personal experience but we were cruising with a friend and his new Islander Bahama 30. It had a 2 cylinder diesel- I forget the brand. While entering port in a following sea his engine stopped running. It turned out to be a blown head gasket. Islander didn't install an anti siphon loop and ran the exhaust right down in the bilge. There were negative pressure pulses in the exhaust bcause of the two cylinder configuration which sucked raw water right up into the engine.

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Old 05-06-2009, 05:35   #6
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"Being abit new to this type of cooling, I had the hose ON for a bit when I was playing with the engine trying to get it running and after a wack of failed attempts."




Good chance you filled the muffler with water and it backed up into the engine. The engine needs to be running to blow the water out the exhaust.

3gm30 Yanmar full of hose water....


Volume of the section of hose out of the muffler to the point of the top of the rise needs to be less than the volume of the muffler.

http://www.practical-sailor.com/mari...iftmuffler.pdf

Catalogue 2009 - USA
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Old 05-06-2009, 09:58   #7
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ok not so much lift other issues rrrrr

Wow, thanks for the replies,

I will post a pic of this system I have afterwards.

OK, I really only have about 3 ft lift over a length of 12 ft back to the stern. the vetus water muffler is well below the engine, I would say the top is of the muffler is at the bottom of the oilpan.

"Also, do you have a vented loop on the connection from the engine to exhaust elbow? If not you can siphon water into the engine past the cooling pump impeller."

NO I don't see any vent if you are talking about one on the water line that leads from the heat exchanger and dumps into the exhaust... its a straight shot in...

The muffler exhaust system used IS Highlited in the manual BUT in the diagram that is highlited there appears to be a vent that is on top of the 6" tall loop for the raw water between the outlet of the exchanger and where it enters the exhaust... this IS NOT how mine is plumbed,.. its a straight 3 inch shot out of the exchanger and into the exhaust manifold.. not a raised loop, no vent...PROBLEM????


My raw water pump is mounted on the front of the engine and is run by a shaft with a drip area inbetween, there is no way water can get in via the raw pump.


I think you are right and I sent the fresh water into the engine so that is a different dumb thing I did.

I got very bad news this morning from the machine shop, the EXHAUST PORTS are very eaten up, so are the exhaust valve stems.
He says it looks like salt water was laying in there for a long time after she was stored....

His boss won't allow him to reassemble it for me to run because of the liability.
He said it pressure tests OK and it is not warped but its a guess on how long it will last. He said IF I HAVE TO RUN IT,..... I will need to lap the valves because the mating surfaces are still decent.
The valves were moving freely when I was cranking the engine but if one breaks while running, I think it will destroy the lower end. This engine does not have sleeves and a set of oversized pistons are $1200.

I'm guessing that this is the same problem that eventually killed the old engine.

I have a 4 inch thick book with absolutely every reciept and manual for every item down to toggle switches and diagrams and wiring harness, and letters to MFG's and replies and on and on.

The muffler exhaust sysem used is Hightlited in the manual and the fellow was a very thorough person, he checked most things to the Nth before proceeding, even sending patch test materials to labs for analysis before using products.

Although he obviously missed something here or something broke down somewhere.

The lower end is OK, I pulled the engine in the boat via a proper lift the owner built in and honed the cylinders , cleaned every thing and reassembled,.. its back in place and ready to reassemble,...HA HA now!

I am in a Jam on the boat as the yard wants it moved, that was part of the deal when buying,.. not to mention its at the most expensive" YACHT YARD"
on the east coast... lucky me, and she's not in the work area either... lol

I was trying to get her mobile so I can take her ten miles down the coast to a "BOAT YARD" that is more work friendly and 1/4 the cost to do the other repairs..... after 200 minutes of cell calls I finally found a head gasket and had it sent from california overnite... it should be here today just in time to get the dead head back...

I hate to risk running this head, waste a $150 gasket, all this work then destroy a jug or two ta boot, options are slim though.

Not to mention now there is still this raw water issue getting back into the exhaust ports. That IS whats going on I think.

Anyone got a decent used head handy, ...built by AMC, for vetus in Holland for a rarely imported french peugeot diesel, LOL

Just in case I'm gonna post an ad for a head for a used cylinder head for a Vetus P4.25... and hope for the best.

Still gotta figure out this raw water thing that vented loop???

...Kev
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Old 05-06-2009, 10:28   #8
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The vented loop is only needed if the engine is below the water line. Look at the two pictures in the Vetus catalog I linked, one is above, the other below the waterline.

John
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Old 05-06-2009, 11:03   #9
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Where the cooling water enters the elbow really shouldnt be your problem.... the exhaust blows it past that point. Those vetus waterlift mufflers are really small.... at leas t the ones I've seen... and 12 ft of hose could be filling that up...
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Old 05-06-2009, 12:15   #10
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Old 06-06-2009, 09:47   #11
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not vented and 20 inches below the waterline

I measured today and found the exhaust manifold and exchanger to be 20 inches below the waterline, the muffler is well below the engine, about the middle of the oil pan is = to top of muffler.

The muffle is a pretty big one, not sure of actual volume yet but I would bet that it probably CANNOT hold the volume of the last 10-12 feet of the exhaust hose, My exhaust is 2.5 - 3 inches in diameter.

I will be checking this by back filling while disconnected from the engine.

I still don't like the idea of raw water only 6 inches from the inside of my engine via exhaust ports... I might plan to move the injecting site further down the pipe and run metal to that point.

Is there such a thing as a flapper valve that would keep water from going the wrong way,.. even if i find the culprit somewhere else,...seems like a good Idea if it didn't clog up and was on a downhill run.
..HMMM

Kev
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Old 06-06-2009, 13:03   #12
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usually a high riser is used in applications like yours. The exhaust elbow should be looped up rather than angled down. Also a loop above the hull exit point should be used.
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Old 06-06-2009, 16:41   #13
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Diagram/Photos?

Could you post a diagram or two and maybe a couple of photos?
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Old 06-06-2009, 18:26   #14
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Kev,

From all your descriptions, I feel fairly sure that your problem is indeed syphoning water through the inlet system and into the exhaust as described in several posts above. With a 20" syphon head, the conditions are very good for this to happen (we had a similar experience on Insatiable I's BMW 35, but were lucky enough to catch it before doing permanent damage).

The vented loop, which must reach above the w/l, will cure the problem. I agree that running a small hose (we used 3/16" diam as I recall) into the cockpit scupper is the best way to do it. But, for the short term, if you need to move the boat under power, simply turning off the seacock on the raw water inlet when the engine is shut down will prevent further damage.

Have you had a look at the suspect exhaust valve stems? The mechanic may be concerned about oil leakage past the stems (due to the corrosion) rather than having a valve head fall off. This oil leakage would be bad in the long run, but not fatal to the engine like a broken valve might be.

As to the head gasket -- what material is it? Our old BMW had solid copper gaskets with o-rings around water and oil passages. If yours is similar, one can with caution re-use the copper part. It is necessary to anneal the copper to soften it back up a bit. We did this by putting a layer of carbon-black all over the gasket (used an acetylene flame from a welding torch without any oxy to smoke it up). Then heated the gasket up just hot enough to burn off the carbon, and let it cool slowly. This will remove any work hardening that the copper received. Then of course you must replace all the o-rings. This method should easily be good for your proposed short trip, and wouldn't waste your expensive new gasket.

At any rate, hang in there... better times are coming!

Good luck and cheers from

Jim and Ann s/v Insatiable II lying Manly Qld Oz
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Old 06-06-2009, 20:02   #15
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Yup! I admit it, I've had it happen to me as well. Following seas, hammering incessantly at the exhaust, pumps water up the tube, fills the exhaust muffler, then rises up and into the exhaust elbow and ruins your whole day. Doesn't take much. My solution? Just before the water and exhaust exit through the hull, I inserted a 2" nylon ball valve. The engine is shut down when we go to sea (in real seas, not mild stuff) and the valve is closed, then the ignition key is hung from the valve. In a crew overboard or other nasty situation, it takes only a moment to open the valve, retrieve the key, and dash to the cockpit. The delay is better than having an inoperable motor with the key in place. It's handy security, as well.
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