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.

If it is original in salt water then it is overdue for replacement.

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.

fryedaze said:

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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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.

Regards,

Pete

Agree with Dave. You're on borrowed time with those risers.

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

TowLou said:

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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What does that have to do with the exhaust riser?

fryedaze said:

What does that have to do with the exhaust riser?

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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.

O C Diver said:

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

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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

Another older shot of post side.

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

Ted I’m 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 fiend’s stock Cummins elbows that were 20 years old They were perfect. No corrosion, no signs of any effects on the welds. And I’m pretty good at that stuff. And they were run in salt water every season ( and flushed well prior to winter haul out).

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

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:





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

O C Diver said:

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:



View attachment 131127



View 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

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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.

jleonard said:

Ted I’m 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 fiend’s stock Cummins elbows that were 20 years old They were perfect. No corrosion, no signs of any effects on the welds. And I’m 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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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.

Regards,

Pete

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.

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.

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.

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.

Good points Maerin, but I would correct that the mixer, aka showerhead, is raw water cooled and this is where the problem occurs and this is Cummins OEM part. The mixer is the part that Tony talks about "doomed to fail". I am having Tony's team build a new exhaust from the turbo to the muffler and the quote is over $3k, this includes moving the mixer farther down stream and increasing the height out of the turbo so it is very unlikely any water could ever make it back up stream to the turbo. I also received quotes from just about anyone I could find in the SE and seaboard still beat them at the end and my engine is a 6BTA Diamond Series.

I agree with others, probably don't owe you anything at this point.

As an aside, I'd add, the angle at the point of injection looks very shallow in your case, shallower than Cummins required 15 degrees, I'd check that before having new ones made.

Some would ask, 'it's been this way all these years why change it?' I've seen cases where it took years of operation to get water to run the wrong way up a non-compliant design, it may be one in a million, but eventually the law of averages catches up with you. Comply with the manufacturer's requirements and it's far less likely to occur. More on the design requirements here https://stevedmarineconsulting.com/wp-content/uploads/2014/03/ExhaustSystems170-FINAL.pdf

Also, given the choice the insulation around the dry part should be an easily removable blanket rather than the wrap. The purpose made blanket usually works better too, what ever is used it has to remain below 200F surface temp throughout the rpm range.

Thank you all for the valuable advice. My plan of attack will be to remove the riser and nozzle, unwrap it , inspect and use a D- meter to measure thickness.

As for the injection angle, it is better than 15 degrees.

You will have to wait until next spring for an update. I am going to roll the dice and put another 300 hrs on her before I inspect.

Dave,
Your boat, your engines, etc., so you decide. However, my free advice (worth every penny) is at least pull them (at least the part where the exhaust water is injected), and give them a thorough cleaning (eg. at the radiator shop) and inspection. As others have stated, including Steve D., having raw water run back into your turbo or worse yet your engine can lead to very large repair bills.P.S. I usually error on the side of caution for most things

Whatever you decide, I hope it works out well for you!

fryedaze said:

Thank you all for the valuable advice. My plan of attack will be to remove the riser and nozzle, unwrap it , inspect and use a D- meter to measure thickness.

As for the injection angle, it is better than 15 degrees.

You will have to wait until next spring for an update. I am going to roll the dice and put another 300 hrs on her before I inspect.View attachment 131224

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Hi Dave,

What's a "D-meter"?

And, as Firehoser and others have stated, it's your boat and your money. Personally, I wouldn't wait to R&R those exhaust components. Lots of risk, little reward in waiting.

Regards,

Pete

jungpeter said:

Hi Dave,



What's a "D-meter"?



And, as Firehoser and others have stated, it's your boat and your money. Personally, I wouldn't wait to R&R those exhaust components. Lots of risk, little reward in waiting.



Regards,



Pete

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D- meter measures metal thickness.
I appreciate everyone's caution. I am not concerned about potential water in the turbo. If it was possible it would have happened in 33 years and 6500 hrs. You guys can say I told you so if it fails. I will let you know if it does. If not you will get my results next year.

Pulled the port exhaust today. This was part of my interference removal for the fuel tank replacement. So far it looks to be in excellent shape, but I haven't got the hose off the spray nozzle. I will post more pictures when I get the exhaust hose off.View attachment 140766View attachment 140767View attachment 140768

Dave,
One last word of caution. My old exhaust elbow looked great (almost new looking) on the outside. It was an original Cummins stock (installed when the boat was built) SS elbow that was then about 16 years old with approx. 2000 hours on the engine. When it came back from the radiator shop all "cleaned up" with the interior carbon and soot build up removed, there were several visible interior perforations (leaks), causing the cooling shower spray pattern to no longer be as effective as designed. There was no visible leaking or any other exterior signs of trouble. The only thing that warned me that I had a problem starting was an exhaust hose overheat alarm I had installed. The hose was staring to "cook" (in spots), and if left long enough it could have failed flooding the bilge and ER with hot salt water and exhaust gases!
As troubling as that could have been, my factory installed "setup" was what Tony Athens terms "doomed to fail", and again if left, could have led to salt water entering my turbo (a fairly common problem) or worse yet entering the engine itself though the exhaust manifold. Luckily, despite this poor installation setup, no damage was done to either the turbo or engine. I got lucky, and I don't like to rely on luck! I replaced the Cummins elbow with a custom made dry elbow to ensure that the water was injected BELOW the level of the turbo, effectively using gravity to protect my important equipment (water does not like to run uphill ). Tony Athens has good info on exhaust design on his website (sbmar.com), and Steve D. has given good info and advice as well.
I suggest giving this (all the info and advice and your equipment) a good checkover to potentially save a (big) future issue.
Again, your boat, your money, your time. Good luck.

firehoser75 said:

Dave,
One last word of caution. My old exhaust elbow looked great (almost new looking) on the outside. It was an original Cummins stock (installed when the boat was built) SS elbow that was then about 16 years old with approx. 2000 hours on the engine. When it came back from the radiator shop all "cleaned up" with the interior carbon and soot build up removed, there were several visible interior perforations (leaks), causing the cooling shower spray pattern to no longer be as effective as designed. There was no visible leaking or any other exterior signs of trouble. The only thing that warned me that I had a problem starting was an exhaust hose overheat alarm I had installed. The hose was staring to "cook" (in spots), and if left long enough it could have failed flooding the bilge and ER with hot salt water and exhaust gases!
As troubling as that could have been, my factory installed "setup" was what Tony Athens terms "doomed to fail", and again if left, could have led to salt water entering my turbo (a fairly common problem) or worse yet entering the engine itself though the exhaust manifold. Luckily, despite this poor installation setup, no damage was done to either the turbo or engine. I got lucky, and I don't like to rely on luck! I replaced the Cummins elbow with a custom made dry elbow to ensure that the water was injected BELOW the level of the turbo, effectively using gravity to protect my important equipment (water does not like to run uphill ). Tony Athens has good info on exhaust design on his website (sbmar.com), and Steve D. has given good info and advice as well.
I suggest giving this (all the info and advice and your equipment) a good checkover to potentially save a (big) future issue.
Again, your boat, your money, your time. Good luck.

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Thanks Tom, I will figure out how to have it cleaned and the inspect it. The runs and elbow are short so I can see everything. If not I have a boroscope.

Here are some shots of the exhaust, for critique [emoji4]View attachment 140774View attachment 140775View attachment 140776View attachment 140777View attachment 140778View attachment 140779