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Old 03-05-2019, 12:38 AM   #1
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DIY Exhaust Elbows (Cat 3208 NA)

Greetings all.

I've just completed a complete cooling system service that included pulling and de-scaling the exhaust elbows. They weren't as bad as some of the pics shared by other members but were moderately restricted at the spray head. Now the question is how long before they fail?


To buy some time, I drilled/tapped the brass plugs and zincs at the bottom of each elbow and installed petcock drains to eliminate the standing water column at shut down. An added nuisance but cheap insurance.


The plan was to run this season like this and replace them next winter abruptly changed when I dropped and cracked one Saturday loading up to go to the boat. I lightly ground out the hairline fracture and patched it with some S10 sealant. Yesterday I bolted them on and leak tested both engines -success! Shut down, drained each elbow and verified no internal or external raw water leaks on the dropped elbow.


The thought of shelling out around $4500 for new Cat elbows kind of makes my speedo bunch up a bit! I'm considering fabricating new elbows out of some off the shelf sch40 316 fittings. Estimated cost is around $1500. Thoughts?
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Old 03-05-2019, 05:15 AM   #2
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You mention standing water. There should not be standing water in the elbows I wouldn’t think. There are many boats with exhaust systems that are not correctly designed. You might want to contact a fabricator on the west coast that can have a look and re design. May be cheaper than going with Cat.

Here is some good information
https://www.sbmar.com/articles/marin...oomed-to-fail/
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Old 03-05-2019, 07:41 AM   #3
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Did your leak test give you 100.00% confidence that the exterior applied patch would not allow "internal crack" water to migrate back into turbo and engine upon shutdown? Especially after a full day's run.

You might post on boatdiesel for a used elbow. Lots of 3208 archives there to peruse. One guy there that really knows his stuff on your engine is Nautidog. Email him for suggestions. Another smart 3208 guy on TF is Alaska Seaduction. He is in your area. You sound like a pretty smart guy, you'll get there.
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Old 03-05-2019, 09:11 AM   #4
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I agree there should not be any water in the exhaust. A proper system does not add water until the slope turns down towards the exit. Any pipes before that are heat wrapped.
There are multiple riser makes easily found on the web. You make get lucky with your patch OTOH failure will be very expensive.
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Old 03-05-2019, 10:19 AM   #5
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Hi Aft Deck Capt,

Well, just remember the old commercial for ??? that says-"You can pay me now, or you can pay me later". And believe me, paying later for a failure of an exhaust riser is WAY more expensive than fixing it correctly now.

There are multiple reasonably local vendors of exhaust risers for 3208's. OEM CAT risers are probably at the high end of the cost spectrum. For instance, suggest you contact Hatton Marine (https://hattonmarine.com/) in Seattle for their advice, and/or National Marine Exhaust (https://www.nationalmarineexhaust.com/) in Marysville, WA. Both companies can provide you with some sound professional advice on this critical piece of engineering.

Yup, you can butch up a fix on almost anything, and get away with it (or not) for an indeterminate period. Putting monkey dung on a cracked riser and calling it good seems like a reach. But your money, your choice. Having seen first-hand the effects of failed exhaust risers on expensive marine diesel engines, the results ain't pretty, and definitely not cheap.

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Old 03-05-2019, 12:20 PM   #6
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Marine Exhaust Systems of Alabama, Inc. makes stainless replacement exhaust elbows for a lot less than Cat. They also make replacement cast iron marine manifolds for many makes and models.
And there are a number of other companies if you do a search. They usually advertise in https://www.boats-and-harbors.com/ and many commercial users magazines.
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Old 03-05-2019, 01:13 PM   #7
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The cast iron risers will last up to 10+ years. And yes there is standing water in the riser after shutdown. Unfortunately, CAT cast iron is now synonymous with precious metal. $6100 for a set of four if you can find them. I’m in the process of replacing mine with dry risers from green water marine. About half the cost and not subject to leaking into the engine. My old ones will be available a month from now.
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Old 03-05-2019, 01:35 PM   #8
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Quote:
Originally Posted by Aft Deck Capt View Post
Greetings all.

I've just completed a complete cooling system service that included pulling and de-scaling the exhaust elbows. They weren't as bad as some of the pics shared by other members but were moderately restricted at the spray head. Now the question is how long before they fail?


To buy some time, I drilled/tapped the brass plugs and zincs at the bottom of each elbow and installed petcock drains to eliminate the standing water column at shut down. An added nuisance but cheap insurance.


The plan was to run this season like this and replace them next winter abruptly changed when I dropped and cracked one Saturday loading up to go to the boat. I lightly ground out the hairline fracture and patched it with some S10 sealant. Yesterday I bolted them on and leak tested both engines -success! Shut down, drained each elbow and verified no internal or external raw water leaks on the dropped elbow.


The thought of shelling out around $4500 for new Cat elbows kind of makes my speedo bunch up a bit! I'm considering fabricating new elbows out of some off the shelf sch40 316 fittings. Estimated cost is around $1500. Thoughts?



whats your eng sn#?
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Old 03-05-2019, 07:31 PM   #9
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whats your eng sn#?
Big Cat, my engine s/n's are 75V4030 and 75V4032.
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Old 03-05-2019, 07:42 PM   #10
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"Yup, you can butch up a fix on almost anything, and get away with it (or not) for an indeterminate period. Putting monkey dung on a cracked riser and calling it good seems like a reach. But your money, your choice. Having seen first-hand the effects of failed exhaust risers on expensive marine diesel engines, the results ain't pretty, and definitely not cheap."


Pete, I'm with you all the way and will be the first to admit that S10 is monkey dung....with out standing elastomeric properties. Seriously though, the patch was only facilitate the A-Z cooling system leak test and my intent is to remedy this before the season kicks off.


Cheers.
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Old 03-05-2019, 07:53 PM   #11
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Quote:
Originally Posted by Cigatoo View Post
You mention standing water. There should not be standing water in the elbows I wouldn’t think. There are many boats with exhaust systems that are not correctly designed. You might want to contact a fabricator on the west coast that can have a look and re design. May be cheaper than going with Cat.

Here is some good information
https://www.sbmar.com/articles/marin...oomed-to-fail/
Cigatoo, that is a great set of design criteria that Tony has provided and I would follow it to a T if I were starting from scratch.

Unfortunately the Cat elbows do have a full (vertical) length water jacket that holds a column of water at shut down. If I decide to go the DIY route I will simply mimic the existing spray-head down angle which appears to be about 15 degrees. The lower section will by dry and wrapped.


Cheers.
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Old 03-05-2019, 08:18 PM   #12
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Quote:
Originally Posted by sunchaser View Post
Did your leak test give you 100.00% confidence that the exterior applied patch would not allow "internal crack" water to migrate back into turbo and engine upon shutdown? Especially after a full day's run.

You might post on boatdiesel for a used elbow. Lots of 3208 archives there to peruse. One guy there that really knows his stuff on your engine is Nautidog. Email him for suggestions. Another smart 3208 guy on TF is Alaska Seaduction. He is in your area. You sound like a pretty smart guy, you'll get there.
Sunchaser, Thanks. Yes I'm confident that there is no breach of the exhaust passage. Peace of mind is bolstered by the new petcock drains. The plan is to run the boat little if at all in this condition until new elbows are in place. If run, that elbow will be the first to get drained.


I'm reluctant to reach out to Tom (ASD)….he'll want me to varnish something on his boat the next time they come to town!

Cheers.
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Old 03-06-2019, 08:00 AM   #13
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Originally Posted by Aft Deck Capt View Post
Big Cat, my engine s/n's are 75V4030 and 75V4032.

did some quick looking. those sn# come up as turbo charged. if you only need the elbows. they come up as $604 each for just the elbow.
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Old 03-06-2019, 01:50 PM   #14
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Hi Eric,
No matter what else you do, install exhaust hose temp alarms on your exhaust hose right after the water injection point. Most any overheat will show itself first at that location, as well, if your elbow starts to go (no longer mixing properly) it will alarm. Mine saved me from MAJOR expense 2 years ago when my stainless, OEM elbow finally started to corrode through.
I suggest that you read Tony’s articles on “doomed to fail” exhausts, as this what mine was, and they are very common. See sbmar.com under Tony’s Tips. If one of these fails, and goes undetected, raw water could enter your turbo and even your engine costing thousands.
I had Scott at National Marine exhaust make a custom exhaust for about the same price as a new OEM one, and the OEM would not solve the “doomed to fail” issue!
Another option would be to have Seaboard Marine (Tony) make one for you.
Mistakes in this area could really come back to haunt you!
Your boat, your money, and your risk tolerance,
Good luck,
Tom
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Old 03-06-2019, 10:29 PM   #15
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Hi Eric,
No matter what else you do, install exhaust hose temp alarms on your exhaust hose right after the water injection point. Most any overheat will show itself first at that location, as well, if your elbow starts to go (no longer mixing properly) it will alarm. Mine saved me from MAJOR expense 2 years ago when my stainless, OEM elbow finally started to corrode through.
I suggest that you read Tony’s articles on “doomed to fail” exhausts, as this what mine was, and they are very common. See sbmar.com under Tony’s Tips. If one of these fails, and goes undetected, raw water could enter your turbo and even your engine costing thousands.
I had Scott at National Marine exhaust make a custom exhaust for about the same price as a new OEM one, and the OEM would not solve the “doomed to fail” issue!
Another option would be to have Seaboard Marine (Tony) make one for you.
Mistakes in this area could really come back to haunt you!
Your boat, your money, and your risk tolerance,
Good luck,
Tom


I hate the idea of taking Scott’s work at national marine exhaust and not hanging it in the living room for display.
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Old 03-06-2019, 11:26 PM   #16
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did some quick looking. those sn# come up as turbo charged. if you only need the elbows. they come up as $604 each for just the elbow.
Thank you for checking Big Cat, that seems like a good price for factory elbows. I'm expecting a quote tomorrow from my local Cat dealership on 4 elbows and 4 spray rings.
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Old 03-06-2019, 11:38 PM   #17
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Hi Tom, great advice. I'll look into temp alarms regardless of which route I take.

I've been noodling around on ACAD using off the shelf sch 40 fitting dimensions to copy the factory risers and I'll post a drawing in a day or two.
At last tally my material cost would be $800 which includes having 4 flanges CNC milled.
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Old 03-07-2019, 01:18 AM   #18
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Photo

Hi Eric,
You are welcome regarding the exhaust hose alarms. They are relatively inexpensive and very effective. The two brands I am aware of are Borel and Aqualarm.
I have attached a poor photo of the new exhaust. It is dry until the low point where the water is injected almost removing the possibility of water getting into the turbo.
Regards,
Tom
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Old 03-07-2019, 09:19 PM   #19
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Hi Eric,
You are welcome regarding the exhaust hose alarms. They are relatively inexpensive and very effective. The two brands I am aware of are Borel and Aqualarm.
I have attached a poor photo of the new exhaust. It is dry until the low point where the water is injected almost removing the possibility of water getting into the turbo.
Regards,
Tom
Hi Tom,

Looks very good, with smooth bends/transitions incorporating all available vertical space. I don't see how that could improved upon.

I don't have turbos eliminating one point of failure but also nothing to show symptoms of leak back before water reaches the block.
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Old 03-07-2019, 09:32 PM   #20
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Originally Posted by gsholz View Post
The cast iron risers will last up to 10+ years. And yes there is standing water in the riser after shutdown. Unfortunately, CAT cast iron is now synonymous with precious metal. $6100 for a set of four if you can find them. I’m in the process of replacing mine with dry risers from green water marine. About half the cost and not subject to leaking into the engine. My old ones will be available a month from now.
gsholz, you were spot on. Four new CAT risers w/spray plates $6940.32 out the door. I was already inclined to go the fab route but this seals it! The design of the CAT NA riser is proven and reliable so I don't have any reservations attempting a knock off out of stainless. It will be just another project.
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