DIY Exhaust Elbows (Cat 3208 NA)

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
Aft Deck Capt

Aft Deck Capt

Senior Member
Joined
May 18, 2014
Messages
191
Location
US
Vessel Name
Long Shot
Vessel Make
1978 Californian 42' LRC
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?
 
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/marine-exhaust-risers-that-are-doomed-to-fail/
 
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.
 
Last edited:
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.
 
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.

Regards,

Pete
 

Attachments

  • marine exhaust.jpg
    marine exhaust.jpg
    98 KB · Views: 115
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.
 
Aft Deck Capt said:
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?
Click to expand...




whats your eng sn#?
 
"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.
 
Cigatoo said:
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/marine-exhaust-risers-that-are-doomed-to-fail/
Click to expand...

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.
 
sunchaser said:
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.
Click to expand...

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!:D

Cheers.
 
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
 
firehoser75 said:
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
Click to expand...



I hate the idea of taking Scott’s work at national marine exhaust and not hanging it in the living room for display.
 
BIG CAT said:
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.
Click to expand...

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.
 
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.
 
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
 

Attachments

  • 7D91D7A3-8D24-4E9F-A69E-F72BA9866207.jpeg
    7D91D7A3-8D24-4E9F-A69E-F72BA9866207.jpeg
    160.3 KB · Views: 94
firehoser75 said:
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
Click to expand...

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.
 
gsholz said:
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.
Click to expand...

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.
 
Yes, parts specific to the 3208NAs are becoming quite expensive. Talk to Dave Dooling at Greenwater Marine (903) 347-0235. He'll do four exact fit replacement dry risers for less than half your quote. I'm about to install mine.

If you are welding them up yourselves make sure the flange to the exhaust manifold is at least 1/2 inch material to prevent distortion and subsequent leaks when bolting on.
 
Last edited:
gsholz said:
Yes, parts specific to the 3208NAs are becoming quite expensive. Talk to Dave Dooling at Greenwater Marine (903) 347-0235. He'll do four exact fit replacement dry risers for less than half your quote. I'm about to install mine.

If you are welding them up yourselves make sure the flange to the exhaust manifold is at least 1/2 inch material to prevent distortion and subsequent leaks when bolting on.
Click to expand...

Thank you. Greenwater makes a quality product. The flanges would be 1/2".

One thing I have to take into consideration is the cost of the repair as a percentage of the vessels purchase price / value.
 
Last edited:
I found an online machine shop (no affiliation) that provides CAD based software to simplify the accurate description of odd shaped parts such as these flanges. Once the drawing is complete, an instant quote is generated.


In this case a scanned trace of the gasket was uploaded, the hole diameters and centers specified, some trimming and filleting of lines and voila!


The third pic is a proposed fit-up of a knock off riser using off the shelf butt weld fittings. The flange and dry section are 304 while the mixer head is 316 for chloride resistance. Jigs will be required to radially align the up vertical sections relative to the flanges. I'll definitely test fit the first tacked assembly prior to being fully welded.
 

Attachments

  • CAT 125-8486 GASKET.jpg
    CAT 125-8486 GASKET.jpg
    21.4 KB · Views: 74
  • E MACHINE SHOP 3D.jpg
    E MACHINE SHOP 3D.jpg
    28.8 KB · Views: 76
  • RISER FIT UP.jpg
    RISER FIT UP.jpg
    49.8 KB · Views: 109
Looks good. Maybe a bit more upright than the original cast iron riser but should not matter. You'll also need to spec the sea water inlet hose nipple on the bottom of the mixer. Here is my original setup.
 

Attachments

  • 1-IMG_2430.JPG
    1-IMG_2430.JPG
    99.2 KB · Views: 95
Many years ago I built black iron risers for 3208NAs and natural Detroit Diesels. At the time the engines came with a NPT threaded manifold end fitting. Used black iron pipe and weld elbows for the riser part then switched to stainless steel where the water sprayed in. I would do it again in a minute but would try and find a suitable spray ring for the discharge to insure even spray around the circumference of the discharge versus shooting it in one side and hoping for the best. Good lagging on the hot parts, good to go. My recollection is stainless-steel rod runs fine on iron but not the other way around.
 
gsholz said:
Looks good. Maybe a bit more upright than the original cast iron riser but should not matter. You'll also need to spec the sea water inlet hose nipple on the bottom of the mixer. Here is my original setup.
Click to expand...

I'd like to replicate the open 90 of the factory riser but the long radius 3" elbow pushes the assembly nearly to far.

Nice ER! lady Anne is definitely worthy of the Greenwater risers.:thumb:
 
bglad said:
Many years ago I built black iron risers for 3208NAs and natural Detroit Diesels. At the time the engines came with a NPT threaded manifold end fitting. Used black iron pipe and weld elbows for the riser part then switched to stainless steel where the water sprayed in. I would do it again in a minute but would try and find a suitable spray ring for the discharge to insure even spray around the circumference of the discharge versus shooting it in one side and hoping for the best. Good lagging on the hot parts, good to go. My recollection is stainless-steel rod runs fine on iron but not the other way around.
Click to expand...

Thanks for the input, glad to hear you were successful. The initial plan was to replicate the factory hole pattern and size but now wonder if biasing a little more water distribution from the top wouldn't better protect the rubber elbows. I'll have to poke around a little more on CAD.
 
I seem to remember the name Marine Exhaust Systems of Alabama advertising reasonably prices SS risers.
 
Dug this up:

Aft Deck Capt said:
Thanks for the input, glad to hear you were successful. The initial plan was to replicate the factory hole pattern and size but now wonder if biasing a little more water distribution from the top wouldn't better protect the rubber elbows. I'll have to poke around a little more on CAD.
Click to expand...
 
Aft Deck Capt said:
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.
Click to expand...




Sorry for not responding sooner. i lost track of the thread. That price was for the elbows for a turbo charged engine. when i searched your sn# they came back as a turbo charged engine not a na engine. its possible some one changed them to na or its a mistake in the system as the older stuff wasn't documented as well as newer stuff. my price for the na riser shows 1585.00 each. i would continue to explore other options considering the cost of all 4. one thing to keep in mind is added heat to the engine room. for every 1* rise on the intake temp the exhaust will rise 3*. so you may/may not need increase airflow to the engine room. also watch out for dead air space around them so you don't get any localized hot spots.
 
You must log in or register to reply here.

Similar threads

M
Exhaust Mixing Elbow
Replies
10
Views
1K
Maerin
Maerin
Sax
Cat 3208TA's exhaust elbow
Replies
20
Views
3K
Sax
Sax
S
Exhaust alarm sounded. Troubleshooting thoughts??
Replies
16
Views
1K
Greg QS
Greg QS
P
Lehamn 90HP S-pipe catastrophic failure and a great ending sea-story
Replies
2
Views
614
socalrider
socalrider
S
Stainless exhaust manifold repairs?
Replies
13
Views
1K
Steve1.0
Steve1.0

Latest posts

Back
Top Bottom