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Old 08-08-2022, 06:33 PM   #1
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Cummins 6BT5.9M exhaust riser expected life

Our 210HP 6BT is 33 years old and has 6500 hrs. It has run 99% of it's life at 1500 rpm. Anyone have experience on lifespan of these risers. I am wondering if I should order new ones. The risers are double wrapped with insulation.
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Old 08-08-2022, 06:57 PM   #2
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If it is original in salt water then it is overdue for replacement.
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Old 08-08-2022, 07:25 PM   #3
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Well to many factors to question. For a real answer get a oil analysis done before a oil change to see what metals are wearing. In addition to that get a compression test done. With those analysis done will give a idea on health. From there she will run till she quits.

To many factors to answer it. To some its a feel. From how fast it starts to how much smoke to how it sounds.
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Old 08-08-2022, 07:25 PM   #4
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Our 210HP 6BT is 33 years old and has 6500 hrs. It has run 99% of it's life at 1500 rpm. Anyone have experience on lifespan of these risers. I am wondering if I should order new ones. The risers are double wrapped with insulation.
My personal rule of thumb on exhaust risers, irregardless of make, model and brand, is remove, clean and inspect every 5 years, and replace every 10. If yours are truly 33 years old, you are long overdue for replacement. Failure to do so can result in multiple, expensive consequences for your engines.

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Old 08-08-2022, 07:26 PM   #5
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Agree with Dave. You're on borrowed time with those risers.
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Old 08-08-2022, 08:35 PM   #6
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A picture would be helpful. Stock mixing elbows are stainless and hold up remarkably well. If it's a true riser, it's probably after market.

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Old 08-09-2022, 01:45 PM   #7
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Well to many factors to question. For a real answer get a oil analysis done before a oil change to see what metals are wearing. In addition to that get a compression test done. With those analysis done will give a idea on health. From there she will run till she quits.

To many factors to answer it. To some its a feel. From how fast it starts to how much smoke to how it sounds.
What does that have to do with the exhaust riser?
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Old 08-09-2022, 02:03 PM   #8
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What does that have to do with the exhaust riser?
Ya know I missed reading you were talking about the risors and not the motor. The cocktail must of been nice and cold after the hot day.
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Old 08-09-2022, 03:03 PM   #9
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A picture would be helpful. Stock mixing elbows are stainless and hold up remarkably well. If it's a true riser, it's probably after market.

Ted
Here is a shot of the port side exhaust. You can see the raw water injection point is at the very end. The riser is stainless. The way it is designed I don't see how it would rust or wear. I am probably being over optimistic because I hate to toss a few boat bucks at this. It will be a custom build and wont be cheap. do these things start to leak or do they just sheer off
Attached Thumbnails
Exhaust Riser.jpg  
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Old 08-09-2022, 03:09 PM   #10
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Another older shot of post side.
Attached Thumbnails
Old Pic Port exhaust.jpg  
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Old 08-09-2022, 03:32 PM   #11
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Dave, those are aftermarket, not stock mixing elbows.

You may want to unwrap one to see if you can come up with a manufacturer's plate. Otherwise they may need to be custom fabricated. Hard to tell from the pictures how the risers are supported, but if a custom replacement is required, you may want to go through the process of assuring the engineering is optimal.

Ted
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Old 08-09-2022, 06:52 PM   #12
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Ted Iím not ready to say the mixing elbows are not stock Cummins.
Clearly the risers are not but the elbows might be
Several years ago I inspected a fiendís stock Cummins elbows that were 20 years old They were perfect. No corrosion, no signs of any effects on the welds. And Iím pretty good at that stuff. And they were run in salt water every season ( and flushed well prior to winter haul out).
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Old 08-09-2022, 07:05 PM   #13
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Well the end of the riser may have a stock mixing elbow, but the riser (which is what was asked about) almost assuredly isn't a Cummins part. Most of the custom risers I've seen, have the raw water mixing section built into the riser.

Ted
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Old 08-11-2022, 01:24 PM   #14
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Dave,

To expand on a point I made earlier, the engineering of custom exhausts has come a long way in the last 30 years. Here are a couple of pics from mine:

Click image for larger version

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Click image for larger version

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Points of interest would include the quality of engineering and workmanship, epoxy heat wrap, and a substantial support from the riser to the transmission mount insuring the support of the riser isn't on the turbo.

Strongly recommend these guys. Their engineering and quality of fabrication is outstanding.

https://www.marine-exhaust.com/

Ted
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Old 08-11-2022, 01:40 PM   #15
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Quote:
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Dave,



To expand on a point I made earlier, the engineering of custom exhausts has come a long way in the last 30 years. Here are a couple of pics from mine:



Attachment 131127



Attachment 131128



Points of interest would include the quality of engineering and workmanship, epoxy heat wrap, and a substantial support from the riser to the transmission mount insuring the support of the riser isn't on the turbo.



Strongly recommend these guys. Their engineering and quality of fabrication is outstanding.



https://www.marine-exhaust.com/



Ted
Thanks Ted, and everyone for the help. I will circle back to this thread with what I do.

To your point on support, my riser is hanging on my turbo.
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Old 08-11-2022, 02:31 PM   #16
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Ted Iím not ready to say the mixing elbows are not stock Cummins.
Clearly the risers are not but the elbows might be
Several years ago I inspected a fiendís stock Cummins elbows that were 20 years old They were perfect. No corrosion, no signs of any effects on the welds. And Iím pretty good at that stuff. And they were run in salt water every season ( and flushed well prior to winter haul out).
And for every anecdote saying "...mine lasted 20 years, and are perfect", there are a zillion failed risers and mixing elbows that HAVE failed, resulting in major damage. But nobody's ego allows posting of THOSE anecdotes.

Virtually all riser/mixer failures are internal to the assembly, and can't be inspected from the outside. That's why periodic removal and cleaning via bead blast or equivalent, and THEN inspecting for corrosion pits, failing welds, cracking, etc. is so important. A job best left to the professionals.

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Old 08-11-2022, 05:49 PM   #17
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I agree with Pete (jungpeter)!
My stock Cummins exhaust elbow failed internally, with NO VISIBLE or other signs of the failure. I only "found the issue" due to an exhaust temperature alarm I had installed. It corroded internally (covered over with soot so not visible even on the inside) and this was only visible or normally detectable after a good cleaning at the radiator shop. If I had not caught this in time, and due to the design of this elbow and installation, it would have allowed saltwater to backflow into my turbo and maybe into the engine! However, due to the fore mentioned alarm, the problem was caught in time. My elbow was 16 years old at that time, and therefore on borrowed time.
Looking at your photos and not having been able to see it in person (for all the angles), I am "concerned " with the water injection point. Much better in OC's photos. Water usually does not flow "uphill".
Check out info on sbmar.com under Tony's Tips for good info on "doomed to fail" marine exhausts.
Good luck with your investigation.
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Old 08-11-2022, 07:22 PM   #18
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What I see in the photo are dry exhaust risers. If these were cast iron wet risers then 10 years max yes. But not knowing what is under the blanket I can’t say anything. I have dry exhaust risers with stainless steel mixing elbows. They are 30 years old and there is no reason to replace them. I think there is a lot of jumping to conclusions here with little facts.
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Old 08-15-2022, 01:01 PM   #19
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I’m going through this right now. The oem Cummins mixers are a bad design and life is about ten years. From the one picture it looks like you could benefit from moving the mixer further down hill to ensure there is no way water can make it back to the turbo and worse into #5&6 cylinders. Good articles about exhaust design under Tonys tips on sbmar.com.
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Old 08-15-2022, 01:18 PM   #20
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Thumbs down

There seems to be 2 terms in use regarding this subject, risers and mixers. I believe risers and mixers are being used interchangeably to refer to the portion of the exhaust connecting downstream of the turbo. I believe nearly al of these devices to be fabricated based on the configuration of the individual boat and engine. For the most part, they are consumables, and how long they last depends on many variables. How they are designed has a lot to do with it.



I don't believe this discussion involves the water jacketed manifold, which would be an OEM Cummins part. They are cooled with engine coolant, and life expectancy should be no different than other parts of the cooling related systems, unless there's a secondary issue that may be creating a problem. Some of the posts may be responses that reference the OEM jacketed manifolds, also sometimes referred to as risers.



I replaced the mixer/riser on my 6BT after about 4000 hrs. due to leakage, and incorporated a re-design to improve on the original design that was specified by the boat manufacturer, and suffered from chronic overheating exhaust problems as a result of the poor design. DeAngelo in FTL was very helpful in the process, which ended the hot exhaust problems for good.



So do your homework. You'll likely have to have a new one made, and now's the time to have a hard look at how the original functions, and implement changes if warranted. I recall the cost was around $1600 about 7 yrs ago. Leakage was the motivation for mine, internal corrosion can be present, undetected, and very serious. If you pop the riser off the turbo flange, there should NEVER be evidence of water getting anywhere near that turbo. Check Tony Athens' SBMar site for discussions on water ingress into the #6 cylinder as a result of poor riser design. That is a must-fix-NOW issue.
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