How to destroy a new $20K diesel

[Scout 30]

There is no exhaust in the heat exchanger, only raw water & coolant.

[Terra Nova]

This is how it should be plumbed.

[brantleychuck]

I may not be understanding one of the pictures, if so sorry. But it looks like the " manicooler" on my beta marine/kubota. A exhaust manifold and heat exchanger in one piece. In the close up picture I see what looks like a end cap to the heat exchanger core. It is very close to your clogged exhaust port . If it is a manicooler and the exhaust manifold and heat exchanger are one cast piece of aluminum I would pressure test the unit. Happy new year !




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[DeepFrz]

I suggested that there might be a leak from the heat exchanger to the exhaust manifold some time ago but he said that if there were it would be a coolant leak and not a salt water leak. I am still suspicious of that.

[ErikFinn]

Originally Posted by FlyingCloud1937

Well clearly there is a problem, If you don't want the same problem after it goes back together, then you better change something.
Start by reading and understand Tonys exhaust tips.
Tony's Tips - Information about Marine Diesel Engines and Boats from Tony Athens

I'll guarantee you its your setup, I would never install as your is.

Lloyd

+1

[hpeer]

Originally Posted by Terra Nova

This is how it should be plumbed.

Right, now overlay that pic on this one.

[hpeer]

Here's another nice one from Yanmar.

Notice how this shows a long horizontal run, lots of volume for water to collect in.

So which diagram is right?

[Wotname]

Originally Posted by hpeer

Here's another nice one from Yanmar.

This is the one I used. No idea if it's best practice or not but as it came with the engine, I just used it.

Maybe it's really bad and I will find out some day

[Captain Bill]

I just had a major failure of the heat exchanger in my Yanmar. The OP is correct in that it is extremely unlikely that a seawater leak could have gotten into the exhaust portion of the casting. The seawater is normally confined to the heat exchanger tubing assembly and the two end caps covering the end of that tubing assembly. A failure of the assembly or the end cap normally results in loss of coolant or an external leak. When the engine is running the coolant is under higher pressure than the seawater and the coolant tend to leak into the seawater side and go out the exhaust. If there is a leak in the end caps the seawater runs over the outside of the manifold and down onto the starter. This shorts out the starter solenoid and burns up the wiring and the starter. It even got hot enough to burn a hole through the top of the solenoid. The leak was obvious after the fact as there was a nice white line of semi dry salt from the point of the leak to where it almost totally encrusted the starter. My engine is only a three cylinder but the manifold/heat exchanger assembly looks the same except he has one more exhaust port. II suppose it is possible that if there was in internal leak in the heat exchanger that the antifreeze/coolant could have slowly been replaced with seawater and that sea water could have corroded a hole in the casting allowing coolant/seawater into the exhaust side. I believe my problem was caused by a small leak that allowed seawater to get behind the O-ring seal The result was galvanic corrosion between the bronze heat exchanger and the aluminum casting. This seal is at the end cap and I would think it would cause an external leak like it did in my case rather than corrode a hole some distance away down near the exhaust ports. That portion of the casting normally only has coolant in contact with it, not seawater.

[DeepFrz]

Okay, another idea bites the dust...lol.

[brantleychuck]

CRACK, the manifold is cracked! Lol


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[wgewaldii]

This thread is one of many which appear here and on SailNet. Are they mirrors of each other?

[DeepFrz]

No, people just post on both.

[Zingaro69]

I really appreciate all the advice and brainstorming. It has allowed me to look at this from many angles. Now if you will indulge me, help me sift through all this and get to the root of the problem.

We ran all the way to PI but I don't remember much in the way of waves crashing into the stern. I had no wind once inside PI so motored 10 hours for 10 days from Cebu to Subic without any sign of engine distress.*

The head has been sent off to be machined and the valve set replaced. The pistons, rings and liner all seem to be good.

I just don't know what to think. *Exhaust manifold completely packed with salt from number four port all the way to the elbow, completely obstructed. But the engine and cylinders not flooded.

Here is my thought process at this point.

1. Many people have suggested that the water lock muffler is too small for the exhaust hose/exhaust run. Also the exhaust run between the elbow and the muffler being too long and or the muffler being in the wrong location. The long hose running down and under the engine to the muffler in front of the engine adds significant volume if the muffler were too small. You would have to fill that entire hose as well as the muffler before it backed up into the engine. But if that were the case it seems to me that the engine would actually flood and if the engine flooded water would not compress and the engine would not have run, what do you think?


2. The heat exchanger: This engine is water cooled. The heat exchanger / exhaust manifold are a single cast so one piece. The raw water/salt water passes through coils that are surrounded by coolant. If they cracked they would only mix with coolant. The coolant and it's reservoir was still full and orange so I have no reason to suspect it had been replaced with sea water.

3. The next suspect is the anti siphon in between the raw water heat exchanger and the exhaust elbow. Again that seems to be fine and if it were a problem any water should drain down and out the elbow, gravity shouldn't bring it back into the manifold. UNLESS it filled the muffler and all the hose between it and the elbow and if that were the case again it seems the engine would actually flood?

4. My best guess at this point is a bad gasket between elbow and the manifold allowing a trickle of water to drip in leaving salt behind but not flooding the engine? The gasket looked fine when it came out. Its a metal gasket, no corrosion, no pits.

The problem broken down is salt in the manifold without water in the pistons. But more specifically salt at the back of the manifold not throughout the manifold. And salt blackened with carbon throughout so probably a long time building?

So with all this clarity can we start over? I'm new and don't have any experience so where my thought process is faulty set me straight.



S/V Thin Wolf

[Cheechako]

Originally Posted by Zingaro69

I really appreciate all the advice and brainstorming. It has allowed me to look at this from many angles. Now if you will indulge me, help me sift through all this and get to the root of the problem.



4. My best guess at this point is a bad gasket between elbow and the manifold allowing a trickle of water to drip in leaving salt behind but not flooding the engine? The gasket looked fine when it came out. Its a metal gasket, no corrosion, no pits.


So with all this clarity can we start over? I'm new and don't have any experience so where my thought process is faulty set me straight.



S/V Thin Wolf

I just don't see this (4 above)as realistic.
BTW, some manufacturers sell a riser to go where the mixing elbow goes for situations where flooding can occur due to a low engine.
It's usually a loop up before descending down. may have a bellows on it. Given no other solution I would be tempted to install or make one. As well as a bigger muffler and or exhaust tubing.