Sorry but…QSM Dry Exhaust Questions

[Richard Lynch]

Seems there are a number of us QSM folks with Dry Exhausts…

No fix seems available to me after all the reading I have found.

Question 1 – What does Cummins suggest after all of these years of common issues with the dry exhausts?

Question 2 – I have seen some threads on a Wet Exhaust Conversion. Is there hope for a resonable conversion?

Thank you for your responses

Topic

[Richard Lynch]

Cummins Does have a TSB on the Exhaust Leaks

See attached.

[Richard Lynch]

Richard Lynch wrote:

Are there any success stories out there?

What I mean is every QSM owner I have ran into that has attempted to mitigate the damage by reducing pitch, watching the Exhaust Temps, etc…still end up with leaking exhausts after spending $5 thousand (+) dollars replacing or trimming manifolds adding longer bolts, etc

I have also trimmed my props in hopes of reducing load, GPH, Temps, etc.

I am not trying to be negative I am just searching for a long term solution.

SBMAR Team:
I spoke with a Cummins Marine Territory Manager from my area last week. He has been with Cummins for 20+ years and was very willing to hear me talk about what I know and my current set up. At the end of the my soap box speech I asked him the burning question (at least in my mind)…what position does Cummins take in the Dry Exhaust issue of the QSM 11.

His response was that Cummins has a NEW Gasket to address these leaks. He also said I was going down the right path by reducing load and re-torquing manifolds and exhaust elbows. He did say once they start to leak exhaust you will not correct that until re-surfacing/shaving/replacing the manifolds.

Once I clean the engine a bit and confirm that the exhausts are still leaking (I know they are) then I will start to budget the new manifolds or at least “New Gaskets” and re-surfacing.

Note – I have reduced pitch by 1.5″ and currently running 2000 RPM and 20.5 MPG with a heavy load.

[Larry Backman]

It’s a 2K hours, 3-5K maintenance item

I’m sorry to be negative on a solution , but I don’t think there is a cost effective one that’s simpler and cheaper than propping down and accepting a 2K lifespan on the manifold gaskets.

I have a fishing friend who works on helicopters at Otis Air Station. He listene for the issue and suggested that with endless money you could do what th3y do with helicopter transmissions and engineer a second coolant Reservoir, add a spiral copper tube around the manifold and take heat away with that. Of course he said that’s probably a million dollar solution 🙂

The other “wet exhaust” solutions Tony has offered up time and again is to go with a 450 HP QSL9, or a 400 HP “wet” QSM. The issue with that is whether you can get by with only 400 HP for your needs. I can’t, I need a bit more as I suspect does a Sea Ray.

It wasn’t that expensive in the grand scheme of things to do both aC and HX service at 3 years/2K hours, and pull the manifold and replace the gaskets as part of that service. According to my mechanic the manifold was fine because we got to the tiny leak in #1 before it totally failed. He also said the same thing Tony said a few months back, the cost of a new manifold is no longer a small fortune, it’s reasonable.

The alternatives in the 700-800 HP range are expensive also. I know the CAT had valve issues and everyone I know who has MANs bitches loudly about the cost of 1000 hr service. I’m jealous of a friend who just dropped a Volvo D11 into his equivalent hull and who is running it much hotter than I dare run the QSM, taking 25-26 GPH out of the Volvo. Time will tell whether that’s a problem for him.

I’m propped at 18 GPH at 1900 RPMs which is just a hair above Cummins specs while light, I’m taking another inch out to get even lower while light and more importantly to get my fully loaded cruise down from 19+ GPH back into the 18 GPH range.

Bottom line, you want solutions – there aren’t easy and cheap ones. The QSM is a pretty impressive base engine at 66% load and 60% of max. Fuel burn. anything you can to do keep heat down will prolong the marinization components lifespan – But ultimately just like MANs, there is a major service cost every 1-2K hours to deal with the starboard side of the engine.

1 user thanked author for this post.

Woo

[Steve Lewis]

Larry Backman

You might reach out directly to Larry. As I recall he has posted the he has gotten ~2000 hours out of his last manifold replacement. I even think he found that it was a munged gasket instead of a warped manifold that lead to his latest soot evidence. He has a single engine I think, and you have twins. The airflow through the engine room and other things are going to be variables that I would guess need to be accounted for when evaluating whether you have trimmed “enough” pitch out of “your” particular setup.

Maybe another 52SB owner will chime in and share the secret sauce. I assume that is what you have.

VooDoo………

[Richard Lynch]

Yes but

Are there any success stories out there?

What I mean is every QSM owner I have ran into that has attempted to mitigate the damage by reducing pitch, watching the Exhaust Temps, etc…still end up with leaking exhausts after spending $5 thousand (+) dollars replacing or trimming manifolds adding longer bolts, etc

I have also trimmed my props in hopes of reducing load, GPH, Temps, etc.

I am not trying to be negative I am just searching for a long term solution.

[Steve Lewis]

one man’s opinion

Since the turbo and exhaust manifold do not have plumbing in them for coolant, one could logically surmise that replacing said turbo and exhaust manifold would be the very beginning of your exercise. That sounds like a lot of money to me………

Why not just reduce the pitch on your props to the point that you are burning no more than 20gph @ 2100 rpm.

Propping the Cummins Marine QSM 11 to Prevent Exhaust Issues

Scroll all of the way to the bottom and read the last paragraph. It is all in there. The other guiding idea is that you “Can Not Under Prop This Engine”.

That is the prescient advice of “The Oracle of Oxnard”. Sorry Tony, I could not help it……. Once you have prop’d down to that point you have a real shot at having your manifolds last. The amount you reduce the pitch will be proportional to the extended length of life. There is no master equation, or ultimate fix, just the idea of getting the burn down below 20gph @~2100rpm. Some will argue the 2100 rpm but based on what I have read, that seems to be reasonable assuming that your boat will move at an acceptable pace in the 1800 – 2000 rpm cruise range accordingly.

Prop down, replace any existing items that are compromised and then start enjoying your boat.

My guess is that this is a whole lot less expensive than trying to convert to wet QSM.

I have had my eye on some Sea Ray 52 Sedan Bridge boats in Lake Michigan and Lake Huron over the past year or so. QSM’s are standard. Some have the MAN upgrades…… It all comes down to what can you accept and deal with. Not to mention afford………..

[Author]

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