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Old 11-05-2014, 06:02 PM   #1
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Can this Yanmar Heat Exchanger & Elbow be saved?

You guys were so helpful with the weak bolts I thought I'd try for more advice.

I've attached two photos

The material on the heat exchanger front around the cap that holds the coolant bundle in place is badly corroded/eroded for about 40% - 50% of the circumference. The O-ring that seals the cap onto the HE face was protruding for about 1/2" of the circumference.

A local welder, with an excellent reputation in the local boating community, says he can rebuild that material and it will be as good as new (after I remove the exchanger bundle).

What would have caused that erosion of the material. There were no leaks at all, I kept a close eye on the cap because it is right above the 135-amp alternator and a leak or drip would be a disaster.

Can the material be re-deposited by a good welder?

The Yanmar Type U mixing elbow has about 1/4 of the upper surface of the inner tube missing. That tube carries the exhaust gas stream to the rear of the elbow where it should join with the raw water flow.

The missing material is downstream from where the exhaust gas stream makes a 90 degree bend to head down to the water lift muffler.

Does that hole cause any problems?
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Old 11-05-2014, 06:16 PM   #2
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Greetings,
Mr. T. I am NOT a welder by any means BUT I have seen some pretty impressive repairs. If the local fellow with the good rep' says he can repair it "like new" I see no reason why it can't be done. You really can't leave it like it is. I expect a new unit would be many $$.
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Old 11-05-2014, 06:19 PM   #3
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I am not that knowledgeable on Yanmars but I am sure someone on here will be. I would ask if you have zincs protecting that area of the cooler?
A leak in that part of the system could be fairly dangerous in bot CO2 and constant water flow.

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Old 11-08-2014, 02:33 PM   #4
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Strongly suggest you go to Seaboard Marine [sbmar.com] and look at his info - article about the Cummins 6bt aftercooler and how it must be maintained. I think the info is applicable here. Tony Athens strongly suggests use of
'ALCO METALUBE',
a heavy coating of it on the areas that seal as the exchanger/aftercooler parts are reassembled.

I cannot tell from the picture but I'll bet you have bronze for the tubes, aluminum for the case. From S.B. photos the caps may be bronze but even so you have corrosion issues. BAD metal mix with seawater although for weight/cost considerations very common.

Even with zincs there will be trouble.

It can be dealt with.

That's why the grease he recommends. I now use it. It is a truly heavy bodied grease that is highly resistant to wash out. Both Yanmar and Cummins assemble these things DRY which is a mistake. Corrosion will eat them. The 'O' rings are simply not enough.

They still need to be disassembled every 2-4 yrs and redone.

http://www.sbmar.com/maintenance-grease-sealants.php
http://www.sbmar.com/articles/aftercooler_-_aftercooler_Disasters
http://www.sbmar.com/articles/aftercooler_maintenance_-_cummins/
http://www.sbmar.com/articles/yanmar_aftercooler_maintenance/

Look around his site. He is also a Yanmar dealer and there is a huge amount of info he offers for free, just the time to wade through it. Even though much is written for Cummins the info has application for all engines.

And others have had the 'O' ring sealing area rebuilt and machined to a suitable surface. It all depends upon the welders and machinists skill , the base condition of the case and the replacement cost whether it is worth the effort or not.

Just for comparison you should contact Yanmar and ask about costs for a new case, tube bundle and complete exchanger. Then you can make an more informed decision.

In fact ask Seaboard also.

Good luck
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Old 11-08-2014, 02:42 PM   #5
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To keep the answers short???????? and a bit limited to each point more or less I will add this note.
While in Seaboards site find Tony's articles about exhaust systems and study it and then compare to yours.

All this is in Tony's Tips.

Elbows do die. However there are things that can shorten their life appreciably with a distinct possibility of damage to the engine depending upon the systems design and mode of failure.
Read/study the article:
Marine Exhaust Systems Overview

Pay particular attention to the orientation of the riser and spray or shower heads where the exhaust is mixed with the raw water.
Then look at yours and see how it compares. You are at the point that any changes needed should be done now.
It may simply be you need a new shower head and a more frequent, much more, inspection frequency.

That missing part in the shower head could lead to a burned exhaust hose. If the water does not mix well with the exhaust gas , then the gasses are not properly cooled, allowing hot gasses to exist and maybe, burn the hose. Replace it, the shower head.
Yanmar may offer a better unit.

David Marchand wrote about his experience although a different Yanmar engine but his experience may be applicable here also.

And ask some more questions if need be. Also more photos showing how it all relates and the shower head's orientation would help.
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Old 11-08-2014, 04:20 PM   #6
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Since I was referenced in the previous post let me chime in:

That exhaust elbow is toast. Replace it, they are cheap enough.

The heat exchanger shell is made of cast iron isn't it? In my experience trying to repair cast iron is a losing proposition. Maybe it is aluminum but I doubt it because it is integral with the exhaust manifold, right? That welder will have to grind deeply into the base material to get absolutely all of the corroded material out, build up the lost material with nickel??? for cast iron or aluminum rod for aluminum and then have a machine shop turn it back down on a lathe to get the O ring sealing face back to original. Will it even fit in a lathe? Would have to be a BIG one to chuck that baby up. Or a big milling machine.

If you don't do it just right, it will leak you will either lose coolant or worse get salt water in your cooling system.

I would replace it.

Did you keep up with the zincs? That would be my guess as to why it failed. What does the bronze cap look like? The raw water had to get to the shell of the heat exchanger somehow to corrode it and the only way seems to be through the end cap that corroded, let seawater past the O-ring and then it ate up the shell.

If that end cap isn't pristine, replace it as well.

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Old 11-08-2014, 05:56 PM   #7
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Dave- Yanmars use aluminum exhaust manifolds, which on this one also holds the cooler bundle. Well know problem corroding where the end caps go. It can be welded up and machined, but not a trivial repair.

You've got a 6LY or 6LP, those both have cu alloy stand-alone coolers. Much better.

Yep, just get a new mixer. Manifold depends on cost and how much damage.
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Old 11-08-2014, 08:18 PM   #8
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Quote:
Originally Posted by ulysses View Post
A leak in that part of the system could be fairly dangerous in bot CO2 and constant water flow. dan
I don't think so. Perhaps you mean CO.
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Old 11-08-2014, 09:14 PM   #9
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Ordered all new parts

Went to another highly recommended welder and machinist. He looked at the manifold / exchanger (he agrees that it is aluminum and the heat exchanger/exhaust manifold are all one casting) after I acid washed it and then pressure washed it. He charges $100/hour and said he could see an easy four to six hours work. He has to grind back the material on both ends of the exchanger to find aluminum that was not salt water damaged. Then he can rebuild the missing surfaces. Then he has to machine the faces to get a flat smooth face for the gaskets.

I have included photos of the front of the heat exchanger.

The exhaust manifold outlet, where the flange bolts to the mixing elbow flange, has some serious erosion also. The welder said there was a lot of salt water damage there and did not know if there would be much original material left after he ground out all the salt water damaged aluminum.

He has done hundreds of similar repairs and says they work fine after they are done.

The Yanmar dealer said he would sell me the new housing / exchanger for $900.

I talked it over with with my wife and she agrees that $500 spent on repairing the old exchanger is not enough savings compared to the $900 for a brand new one.

The welder would not even touch the mixing elbow after he looked at the damage to the inner tube. He said that particular problem leads to salt water getting into the exhaust manifold and then the cylinders. He said anyone trying to repair the elbow would be a fool.

The Yanmar dealer thought I should do some better measurements to see if I could use the standard $250 Yanmar elbow. I did and found that the bottom of the exhaust manifold outlet is only 5" above the water level in the waterlift muffler. ABYC wants 10.5". The $850 HighRise mixing elbow would give me 11" from the bottom of the elbow to the water level in the waterlift muffler.

So - I ordered the $850 mixing elbow
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Old 11-09-2014, 10:11 AM   #10
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Quote:
Originally Posted by Tacomasailor View Post
Went to another highly recommended welder and machinist. He looked at the manifold / exchanger (he agrees that it is aluminum and the heat exchanger/exhaust manifold are all one casting) after I acid washed it and then pressure washed it. He charges $100/hour and said he could see an easy four to six hours work. He has to grind back the material on both ends of the exchanger to find aluminum that was not salt water damaged. Then he can rebuild the missing surfaces. Then he has to machine the faces to get a flat smooth face for the gaskets.

I have included photos of the front of the heat exchanger.

The exhaust manifold outlet, where the flange bolts to the mixing elbow flange, has some serious erosion also. The welder said there was a lot of salt water damage there and did not know if there would be much original material left after he ground out all the salt water damaged aluminum.

He has done hundreds of similar repairs and says they work fine after they are done.

The Yanmar dealer said he would sell me the new housing / exchanger for $900.

I talked it over with with my wife and she agrees that $500 spent on repairing the old exchanger is not enough savings compared to the $900 for a brand new one.

The welder would not even touch the mixing elbow after he looked at the damage to the inner tube. He said that particular problem leads to salt water getting into the exhaust manifold and then the cylinders. He said anyone trying to repair the elbow would be a fool.

The Yanmar dealer thought I should do some better measurements to see if I could use the standard $250 Yanmar elbow. I did and found that the bottom of the exhaust manifold outlet is only 5" above the water level in the waterlift muffler. ABYC wants 10.5". The $850 HighRise mixing elbow would give me 11" from the bottom of the elbow to the water level in the waterlift muffler.

So - I ordered the $850 mixing elbow
You made the right decision and won't regret it. That is a great price on the HE and, the new mixing elbow will be a much safer solution. Good moves all the way around. . .
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Old 11-09-2014, 12:55 PM   #11
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You made the right decision and won't regret it. That is a great price on the HE and, the new mixing elbow will be a much safer solution. Good moves all the way around. . .
I agree.....one less thing to ever worry about.
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