Thoughts on Exhaust Manifolds

[BDofMSP]

I'm planning and budgeting for the inevitable replacement of my exhaust manifolds and elbows, as the boat is over 20 years old - nothing lasts forever.

My question is "How important do you think it is to use OEM for the manifold"? I mean, the price isn't even in the same universe. Cummins (and Seaboard Marine) want almost $6k for a manifold. They can be commonly found from many manufacturers and distributors across the internet for $600 to $800 bucks.

There's nothing really "mechanical" about it - it's a piece of steel. Is there really that much difference here? I thought about looking for reviews and such, but other than basic fit, any differences (from inferior steel, etc.) wouldn't likely show up for years.

I'm not opposed to spending some extra money, but this is an enormous difference, and that money could be the labor for the job. I'd like to know specifically why one is worth ten times the other.

Thanks,
BD

 

[SeaLion]

What engines do you have?

 

[O C Diver]

I'm planning and budgeting for the inevitable replacement of my exhaust manifolds and elbows, as the boat is over 20 years old - nothing lasts forever.

My question is "How important do you think it is to use OEM for the manifold"? I mean, the price isn't even in the same universe. Cummins (and Seaboard Marine) want almost $6k for a manifold. They can be commonly found from many manufacturers and distributors across the internet for $600 to $800 bucks.

There's nothing really "mechanical" about it - it's a piece of steel. Is there really that much difference here? I thought about looking for reviews and such, but other than basic fit, any differences (from inferior steel, etc.) wouldn't likely show up for years.

I'm not opposed to spending some extra money, but this is an enormous difference, and that money could be the labor for the job. I'd like to know specifically why one is worth ten times the other.

Thanks,
BD

Are you talking about the wet exhaust elbow or the water cooled exhaust manifold (which is cooled with engine coolant antifreeze)?

Ted

 

[BDofMSP]

What engines do you have?

Cummins 8.3 6CTA 450 Diamond's

 

[BDofMSP]

Are you talking about the wet exhaust elbow or the water cooled exhaust manifold (which is cooled with engine coolant antifreeze)?

Ted

I'm planning to replace both, but in this case I'm referring to the coolant filled exhaust manifold.

 

[jungpeter]

I'm planning and budgeting for the inevitable replacement of my exhaust manifolds and elbows, as the boat is over 20 years old - nothing lasts forever.

My question is "How important do you think it is to use OEM for the manifold"? I mean, the price isn't even in the same universe. Cummins (and Seaboard Marine) want almost $6k for a manifold. They can be commonly found from many manufacturers and distributors across the internet for $600 to $800 bucks.

There's nothing really "mechanical" about it - it's a piece of steel. Is there really that much difference here? I thought about looking for reviews and such, but other than basic fit, any differences (from inferior steel, etc.) wouldn't likely show up for years.

I'm not opposed to spending some extra money, but this is an enormous difference, and that money could be the labor for the job. I'd like to know specifically why one is worth ten times the other.

Thanks,
BD

Hi BD. Please, please don't be THAT GUY that searches out the least-expensive repair parts, particularly for foundational engine parts such as exhaust manifolds, risers, spray nozzles, etc. Yeah, I understand your logic-why spend MY money now, when it'll be the NEXT guy that either benefits from my largess (or much more likely) suffers for your frugality.

As to the specifics of why OEM are more expensive than aftermarket manifolds and other exhaust parts, you simply have to have each in hand, and examine things like machining quality (flatness, in particular), casting quality (including thickness, voids and inclusions, etc. which are hard to measure, but routinely apparent), and fit and finish. And ask yourself how likely is it that "...many manufacturers and distributors across the internet" can manufacture (and provide warranties for) items such as cast iron manifolds for (per your example) an order of magnitude less money. If it sounds too good to be true, it usually is.

If you look closely at aftermarket manufacturers of manifolds, for instance, you'll likely find multiple brands with exactly the same country of origin (China, these days), but possibly different paint jobs and labels, but exactly the same part. With exactly the same shoddy casting quality, post-casting machining flaws, poor fit, and other quality assurance issues that aren't apparent until you have installed the part, and are down the road aways.

"...There's nothing "mechanical" about it..." HUH? It's foundational mechanical engineering design, which doesn't come cheap, or welcomes shortcuts.

Again, please don't step over a dime to save a dollar. Pushing shoddy craftsmanship to the next guy is really cheesy. And given the cost of repairs to exhaust systems are typically labor intensive, the cost of parts should be a second order consideration. And don't forget Ben Franklin: "The bitterness of poor quality is remains long after the sweetness of low price is forgotten".

Regards,

Pete

 

[sunchaser]

If you mean the manifold they may well last the life of the engine as they are coolant cooled. If you mean the aftercoolers they should be pulled every 4-5 years - cleaned, inspected and pressure checked.

 

[BDofMSP]

If you mean the manifold they may well last the life of the engine as they are coolant cooled. If you mean the aftercoolers they should be pulled every 4-5 years - cleaned, inspected and pressure checked.

I already pull the aftercoolers regularly and service them. They are in good condition. I appreciate the comments on the manifold. My thinking was that since I will be replacing the elbow and have the whole exhaust disassembled, I might as well replace the manifold too. Maybe it's simply never necessary and I should leave it be. The engines have about 2200 well maintained hours on them.

Thanks
BD

 

[O C Diver]

I'm planning to replace both, but in this case I'm referring to the coolant filled exhaust manifold.

As Sunchaser mentioned, it's uncommon for the exhaust manifold to fail, maybe more likely if you push the engine hard, don't allow proper warmup, and especially proper cool down after pushing hard.

If you're boat has been exclusively run in freshwater, there's a good chance the wet exhaust elbow won't need replacing either.

Ted

 

[BDofMSP]

Hi BD. Please, please don't be THAT GUY that searches out the least-expensive repair parts, particularly for foundational engine parts such as exhaust manifolds, risers, spray nozzles, etc. Yeah, I understand your logic-why spend MY money now, when it'll be the NEXT guy that either benefits from my largess (or much more likely) suffers for your frugality.

As to the specifics of why OEM are more expensive than aftermarket manifolds and other exhaust parts, you simply have to have each in hand, and examine things like machining quality (flatness, in particular), casting quality (including thickness, voids and inclusions, etc. which are hard to measure, but routinely apparent), and fit and finish. And ask yourself how likely is it that "...many manufacturers and distributors across the internet" can manufacture (and provide warranties for) items such as cast iron manifolds for (per your example) an order of magnitude less money. If it sounds too good to be true, it usually is.

If you look closely at aftermarket manufacturers of manifolds, for instance, you'll likely find multiple brands with exactly the same country of origin (China, these days), but possibly different paint jobs and labels, but exactly the same part. With exactly the same shoddy casting quality, post-casting machining flaws, poor fit, and other quality assurance issues that aren't apparent until you have installed the part, and are down the road aways.

"...There's nothing "mechanical" about it..." HUH? It's foundational mechanical engineering design, which doesn't come cheap, or welcomes shortcuts.

Again, please don't step over a dime to save a dollar. Pushing shoddy craftsmanship to the next guy is really cheesy. And given the cost of repairs to exhaust systems are typically labor intensive, the cost of parts should be a second order consideration. And don't forget Ben Franklin: "The bitterness of poor quality is remains long after the sweetness of low price is forgotten".

Regards,

Pete

It's presumptive to assume that I'm only focused on price, and a bit annoying. I spend thousands, according to my mechanic "needlessly", because I try to make sure my engines are well maintained. And my logic behind that is exactly the OPPOSITE of what you suggest. I'm not going to own this boat forever and I want to make sure it doesn't experience any catastrophic incidents, so I maintain rather than repair. I'm not trying to "screw the next guy".

I appreciate your insights on the quality of the castings, and the accuracy of the machining. While they all have the same 12 month warranty, that doesn't mean there aren't latent quality issues (which I implied I understood by my comments about not relying on reviews). I do agree that there could be differences in those, which is what triggered my question. I was hoping that folks had actual experiences with these, instead of a general feeling that the most expensive is always best.

Regarding the investment in engineering, that ship has sailed. Those manufacturers that copy that design are benefitting from that investment, but their copy of the part contains it. When I said "mechanical" I was implying moving parts which may require precision to maintain durability over the long haul.

I'm not sure I see this as a "if it's too good to be true, it is" situation. In fact the OEM part could easily considered to be "too bad to be true" as it's the only single manufacturer that charges anywhere near this. Dozens of others charge 1/10th of the price and seem to be selling them and staying in business for decades (in some cases). The engine industry absolutely lives and dies on reputation, so I would think there would be tons of lore in the community from people who have been burned by these over and over if they were junk. And maybe there is ... which is why I'm asking. If this was one cheap source, among many others that were similar to the OEM, that would be too good to be true. Given the wide selection I'm just as apt to consider Cummins to be price gouging.

The casting and machining may be inferior, so I'll take that advice to heart. Thanks,
BD

 

[BDofMSP]

As Sunchaser mentioned, it's uncommon for the exhaust manifold to fail, maybe more likely if you push the engine hard, don't allow proper warmup, and especially proper cool down after pushing hard.

If you're boat has been exclusively run in freshwater, there's a good chance the wet exhaust elbow won't need replacing either.

Ted

The boat was in salt for about 13 years of its life.

 

[sunchaser]

Our boat has been in saltwater for 18 years. Two years ago we bore scoped the entire exhaust system. The manifolds looked fine as did the after coolers. We pulled the after coolers anyway for normal servicing.

But, our exhaust manifold temperatures reside in the 500-600F range. If yours are in the 800 range + there may be some additional heat induced metal matrix changes. Then comes into play metal metallurgy, casting, cooling and quenching protocols and the after effects of any overheats.

Quiz Seaboard as to their recommendations. 2,000 hours aren't too many for a non sea water metal application IMHO. Me, I'd change out the elbows just because. After 2,000 hours we did same with a high quality SS fabrication to replace the originals.

 

[firehoser75]

I agree with Sunchaser......quiz Seaboard as to their recommendations and why that recommendation.
Unless there has been a major overheat, I would not expect a problem with the exhaust manifold, and I have not heard of a need for "routine" replacement of that part? As to the exhaust elbow, check out Tony Athens' articles on "doomed to fail" marine exhaust (systems) and how prevalent they are. Do not just "blindly" replace "like for like" (exhaust elbows) without some additional research. Yours may be fine, but it (they) may just be a problem waiting to happen. See Tony's Tips on sbmar.com for more detailed info and it depends greatly on the particular installation on each boat.
Good luck.

 

[BDofMSP]

Thanks for the tips. I have read everything I can on that site, and I'm a member on boatdiesel.com too and have read some things there. Based on my understanding of his principles, I think that the current design is pretty solid.

I will definitely temp the manifolds next time we're underway. We rarely get up on plane with her, other than 3-4 minutes to get out of the way of a sailboat or something. But I would like to run it up for a bit and check the temps to get a sense of where they are at across the whole manifold.

I would be super happy to not replace that part, and based on what I've read here if my temps look good and consistent, I'll likely skip it. Direct that money to a high quality elbow as Sunchaser did.

BD

 

[Portage_Bay]

If it sounds too good to be true, it probably is. On price alone I would not trust a $600 - $800 aftermarket part to replace an OEM or similar $6Kpart. Manifolds are in my opinion and important part of the engine.

Speaking to the risers. They are more of an add-on part. As long as they don't create back pressure and cool the exhuast system well they should be OK. Look around. Sometimes you can do better aftermarket than OEM. Cat 3208 risers are a perfect example. Over $2K each if you can find them and they are cast iron. Doomed to fail. A number of aftermarket risers exist and are made of better materials. Usually cheaper than OEM but not on the price range you are talking about.

Cummins (and Seaboard Marine) want almost $6k for a manifold. They can be commonly found from many manufacturers and distributors across the internet for $600 to $800 bucks.

 

[Comodave]

I would be very leery about a $600 or so manifold. There has to be something way off about that. Also look at the cost of your 6CTA, do you really want a bargain basement price manifold?

 

[BDofMSP]

I would be very leery about a $600 or so manifold. There has to be something way off about that. Also look at the cost of your 6CTA, do you really want a bargain basement price manifold?

I understand that thinking, but it's not matching my experience. In fact OTHER than Cummins, it's been hard to find a single manifold that costs over $1000. I mean not one. $800 isn't an outlier - it's the norm. That was my point earlier. I'm not looking for bargain basement. I'm wondering why one and ONLY one vendor is worth 10x what every other vendor charges.

What I've heard so far is "the quality of the machining". And speculation about voids in the castings and such. I was hoping to hear some actual stories (even 3rd hand) about such issues.

Yes if Cummins was $6k and most places were $4k, and one guy was $800 bucks, then that's way too good to be true. And I'd gladly pay the $6k vs the $4k. But it's simply not been like that in my search so far.

 

[twistedtree]

I agree with others that I would expect an exhaust manifold to last the life of the engine, unless there is some known problem with the specific engine.


As for price, my first question would be to verify that you are looking at a WET manifold, not a DRY manifold. I don't know the specifics for this Cummins and apologize if you have already checked this, but marine variants of engines typically have a water jacket (coolant, not raw water) manifold, where industrial and truck applications have dry manifolds. The cost would be significantly different - along the lines of the price differences you have seen.

 

[BDofMSP]

I agree with others that I would expect an exhaust manifold to last the life of the engine, unless there is some known problem with the specific engine.


As for price, my first question would be to verify that you are looking at a WET manifold, not a DRY manifold. I don't know the specifics for this Cummins and apologize if you have already checked this, but marine variants of engines typically have a water jacket (coolant, not raw water) manifold, where industrial and truck applications have dry manifolds. The cost would be significantly different - along the lines of the price differences you have seen.

Great point. I've been making sure that they list the specific part number for my CPL and indicate "marine" or wet. For example at dieselpartsdirect (which I know nothing about), they list a separate part number that is specifically stated "dry" and it is quite a bit cheaper. Their listing for my part number (https://www.dieselpartsdirect.com/exhaust-manifolds-for-cummins-6cta-isc-and-qsc-engines) does also indicate that the also sell the "genuine" version too.

A different vendor (woodlineparts.com) lists theirs as "water cooled", which I assume means coolant. Theirs is a bit over $600. They list the brand as "Interstate McBee". Another site (big bear engines) lists their version of the same part number, also manufactured by Interstate McBee, as "CUMMINS C SERIES MANIFOLD – EXHAUST – WET PART: 3922935" for about $800.

Many of these sites list the manufacturer as "Interstate McBee". This company has been in business since 1947, and they have six facilities (both manufacturing and distribution) across the country. They employ over 20 people in customer service alone. They are "the world’s leading manufacturer of fuel injector and injector components for EMD and GE engines", and in my book, fuel injector manufacturing is not trivial work. Now granted, their injector manufacturing is likely not the same factory as their manifold casting. But I don't see this as a "fly by night" organization that is distributing garbage to make a quick buck.

But I guess if their manifold is $800 it must be garbage? I know that's not what you're saying, but it seems to be the consensus here so far.

BD

 

[rslifkin]

With that big a price spread, in my mind it's always worth finding out why the expensive option is so expensive. Sometimes it's better enough to be worth it, sometimes it's not. Other times it's just a difference of how long the part lasts, but both work fine within their lifespan. When we're talking $800 vs $4000, even if you play it safe and replace a seemingly good $800 manifold after half the time you could expect the $4000 one to last, you've still come out ahead (assuming the labor involved in replacement is reasonable).

 

[Circumnavigator]

I am in agreement with the several of our members who think it's almost certainly not necessary. Fintry's original Perkins 6-354 had a seawater cooled exhaust manifold, which holed through at just shy of fifty years of age. I would be very surprised if a freshwater cooled manifold failed.


Jim

 

[BDofMSP]

There's definitely consensus on that, so I think I'll modify my plan and focus on the raw water cooled components. Thanks for all the insights.

BD

 

[BDofMSP]

Thought I'd add a picture of one of the current mixers. There might be an opportunity to improve this but it seems reasonable to me. Interested in feedback. Sorry but I don't know how to rotate it clockwise 90 degrees.

 

[twistedtree]

Great point. I've been making sure that they list the specific part number for my CPL and indicate "marine" or wet. For example at dieselpartsdirect (which I know nothing about), they list a separate part number that is specifically stated "dry" and it is quite a bit cheaper. Their listing for my part number (https://www.dieselpartsdirect.com/exhaust-manifolds-for-cummins-6cta-isc-and-qsc-engines) does also indicate that the also sell the "genuine" version too.

A different vendor (woodlineparts.com) lists theirs as "water cooled", which I assume means coolant. Theirs is a bit over $600. They list the brand as "Interstate McBee". Another site (big bear engines) lists their version of the same part number, also manufactured by Interstate McBee, as "CUMMINS C SERIES MANIFOLD – EXHAUST – WET PART: 3922935" for about $800.

Many of these sites list the manufacturer as "Interstate McBee". This company has been in business since 1947, and they have six facilities (both manufacturing and distribution) across the country. They employ over 20 people in customer service alone. They are "the world’s leading manufacturer of fuel injector and injector components for EMD and GE engines", and in my book, fuel injector manufacturing is not trivial work. Now granted, their injector manufacturing is likely not the same factory as their manifold casting. But I don't see this as a "fly by night" organization that is distributing garbage to make a quick buck.

But I guess if their manifold is $800 it must be garbage? I know that's not what you're saying, but it seems to be the consensus here so far.

BD

That does sound like a credible company, and it sounds like you are on the wet vs dry difference. If it were an Alibaba vendor I would ignore them, but in this case I'd probably give it a try. For all we know, that's who makes them for Cummins

 

[Tiffany]

The Peace of mind Stainless Steel over Cast iron manifold

I'm planning and budgeting for the inevitable replacement of my exhaust manifolds and elbows, as the boat is over 20 years old - nothing lasts forever.

My question is "How important do you think it is to use OEM for the manifold"? I mean, the price isn't even in the same universe. Cummins (and Seaboard Marine) want almost $6k for a manifold. They can be commonly found from many manufacturers and distributors across the internet for $600 to $800 bucks.

There's nothing really "mechanical" about it - it's a piece of steel. Is there really that much difference here? I thought about looking for reviews and such, but other than basic fit, any differences (from inferior steel, etc.) wouldn't likely show up for years.

I'm not opposed to spending some extra money, but this is an enormous difference, and that money could be the labor for the job. I'd like to know specifically why one is worth ten times the other.

Thanks,
BD

For my Perkins T6-354, I looked at the cost (~$2,300) of the factory cast iron manifolds, which should be replaced every five years. To my mind they are a ticking time bomb and as seen on most marine engines, the source of major failure when they begin to leak, undetected, and allow water ingress into the engine.

I made the decision to forgo that uncertainty and order a Stainless steel replacement from Marine Exhaust of Alabama - a TIG-welded, 1/4" 316 stainless, bolt on replacement. Cost $6,000, but has already given me 6 years without worry about a pinhole leak that destroys the engine and leads to a $20,000 engine rebuild. These units see 20 years + use on commercial boats in the Gulf of Mexico. SS is cheaper in the long run - and even in the short run.

 

[sunchaser]

For my Perkins T6-354, I looked at the cost (~$2,300) of the factory cast iron manifolds, which should be replaced every five years.

Are you referring to a salt water cooled manicooler. Those so equipped engines were no longer made by the late 90s replaced by Perkins Sabre with coolant cooled exhaust manifolds that are good or many decades.

 

[djewell]

Reliable Exhausts

I had a problem with my exhaust elbow/mixer a couple of years ago while cruising in FL. Found Marine Exhaust Systems of Alabama (Marine Exhaust Systems of Alabama, Inc.), Mark Coulson, owner. Worked out the details over the phone and they fabricated a custom wet elbow exhaust in about a week and shipped it to my location in Ft. Pierce, FL. Fit perfectly and works great.


I recommend them, hands down.


Good luck,
Doug

 

[Slowmo]

We moved to aftermarket risers for our Cat 3208's because the OEM part had become outragiously expensive (order of $3000 each). We used Greenwater stainless with a ceramic coating on the interior. These have worked perfectly and will outlast us. My mechanic was much less concerned about the exhaust manifolds, his experience was problems with risers getting old.

 

[twistedtree]

For my Perkins T6-354, I looked at the cost (~$2,300) of the factory cast iron manifolds, which should be replaced every five years. To my mind they are a ticking time bomb and as seen on most marine engines, the source of major failure when they begin to leak, undetected, and allow water ingress into the engine.

I made the decision to forgo that uncertainty and order a Stainless steel replacement from Marine Exhaust of Alabama - a TIG-welded, 1/4" 316 stainless, bolt on replacement. Cost $6,000, but has already given me 6 years without worry about a pinhole leak that destroys the engine and leads to a $20,000 engine rebuild. These units see 20 years + use on commercial boats in the Gulf of Mexico. SS is cheaper in the long run - and even in the short run.

Does salt water run through the manifold somehow? If not, I'm struggling to understand why a 5 year replacement interval is required.

 

[Tiffany]

My Perkins is a 1982 model T6-354 with a raw water-cooled manifold, not equipped with the manicooler, not coolant-cooled. Going back to my initial remarks, and in conversation with a marine mechanic, his recommendation for exhaust systems - despite their higher purchase cost - is for stainless upgrade over cast iron, when available.