QSM11 635 Overhaul

[Jerome Billett]

I’m looking at a Novatec 55 with 15 year old QSM11s. The boat is great but as far as I can ascertain, the engines have had none of the recommended preventive seawater side component maintenance that I know is important after learning about on this Forum and BD (and doing) everything I possibly could on the Cummins 6Cs I had on my previous boat.
The turbos and lower half of the aftercoolers are pretty toasty. (see attached photos). I see no soot around the exhaust area suggesting the dreaded leak.
I don’t like the look of the exhaust elbow orientation and would appreciate comments from the experts here. (see attached)
So to feel comfortable before taking this boat on a long cruise, I expect to:
1) pull the coolers- HX, AC, Gear Oil- and service at shop
2) replace all the hoses and gaskets etc. when things put back together (and any others)
3) Check valve lash
4) Replace all filters that haven’t been done recently
5) Service/rebuild the seawater pumps
6) Service turbos?

Any other items to list?

Purportedly the annual stuff like oil change, fuel filters etc is up to date.

So anybody know a ballpark figure of associated costs for the above? I’m guessing $20K if contracted out.
Also, I was able to do all this work (except valve lash) on my 6Cs myself. Is there anything special about the QSMs that I couldn’t handle?
Are there exploded views of the engines anywhere to show all the bolts etc to access to remove these components?
Any and all other comments appreciated before I put an offer on this rig.

Topic

[Tony Athens]

No problem ………….Actually I have to respect the older 72’s–It was a solid engine engine as long as you watched over all the hang-ons closely and could afford the parts..

Tony

[Jerome Billett]

Lost It

Just to close this discussion, seller would not cooperate on any work or price adjustment to address the exhaust manifold leak. With many unknown concerns about the engines I had to pass. Sad. I loved that boat.
Went ahead and bought the Jefferson with frickin’ Volvo 72s.
I’m so gonna miss my Cummins and all the great info and feedback on this forum.
It’ll be a big learning curve again.
Will you guys still talk to me if I post?

[Larry Backman]

Single engine downeast

I have a 1.5:1 gear, 23,000# boat, when I bought the boat it was severely overpropped at 26 x 26, 4 bladed dynaquad prop. I was burning 20 GPH at 1825 RPM and only made 2280 RPM WOT. . I cut it to 26 x 25, hit WOT correctly but still burned too much at cruise, then cut it to 26 x 24 to get it right.

Amusingly it stayed on 3 years after being cut to 26 x 24. I had it pulled, rebalanced and tuned last winter and found it was actually 26 x 24.5. I’m pulling it again this winter and going down to 26 x 24 to get lower on the prop curve. So what if I lose another half knot off the top.

[Jerome Billett]

Thanks for the info Larry. What props do you have and how much adjustment (pitch, diameter) was made to get the specs you wanted?

[Larry Backman]

I hear you/Went down to 610

I propped down to the 610 curve with the new 670 engine.

FWIW, not suggesting it’s right but when Cummins NE came out to replace my manifold under warranty last year their viewpoint On the subsequent sea trial was that I was fine as my 1875/17.5 GPH at cruise 31 GPH/94% load at WOT was perfect.

I asked them repeatedly about Tony’s 18-20GPH max rule and they said they have many QSMs 670s that run at 2000 RPM/21 GPH with no problems.

They were more concerned ( as was I) about that funny 12 knot1500 RPM in between speed when the boat was not on plane and above the fuel curve. The advice was to avoid those speeds and stay in my 1875 sweet spot as much as possible.

[Tony Athens]

Propping—————–That is the best way to mitigate the issue BEFORE you redo the manifolds. Don’t wait until after.

The graph here is from a QSM 535 –This engine rarely had manifiold turbo issues..

[Larry Backman]

2x QSM 7 year QSM owner here wants answers also

1400 hrs in on my 2nd exhaust manifold on a 2016 reman QSM. The initial one failed at 175 hrs. I would love factory advice also on both the proper way to have it fixed when it fails and also how to best care for it.

I can live with it as a wear part because as tony says, it’s a great engine core.

[Jerome Billett]

Thanks again Tony. So if I make sure to prop to 18.6 GPH or below at 2000 rpm before the manifolds are fixed then I might avoid this in future? Is that advice still accurate and recommended?

[Tony Athens]

QSM 11 Dry Manifold Leaks

Welcome to the “QSM11 Dry Manifold & Dry Turbo World” of just about impossible to fix exhaust leaks..

IMO, there is no sure fire solution.. Only ones to help mitigate the problem from reoccurring..

Since the factory is now monitoring this site closely and what I post personally, maybe a factory guy will chime in and help us learn the latest on how to deal with this issue that has been around since 1999 (29 years) ..

Great engine, very efficient, extremely compact compared to its competitors, parts are easy & cheap, and service is easy for DIY guys, and all this together makes it a desirable engine to own, EXCEPT we have one BIG BUT ——— the on-going exhaust manifold leaking issues………

Tony

[Jerome Billett]

OK, got some more pics to confirm the exhaust leak. I should have had a better light. So question now is, do I have to fix it?
And if coolers are coming off anyway, does that make the job much more straightforward or is there a lot of other dismantling to do to access the manifolds?
And is that turbo been heated up way too much?
Thanks in advance….

[Jerome Billett]

No more pics. My camera battery died at a critical moment of all things!

[Rob Schepis]

Jerome Billett wrote:

Thanks Tony for the prompt reply. I will take this opinion into account. Around the lifting eye it was discolored a little black in spots but not “sooty”. It was like baked on dirt. Is that the sign?

Sounds right, have any pics?

At least it looks like you have ample overhead engine room space for a safe dry riser..

[Jerome Billett]

Thanks Tony for the prompt reply. I will take this opinion into account. Around the lifting eye it was discolored a little black in spots but not “sooty”. It was like baked on dirt. Is that the sign?

[Tony Athens]

Looks to me like plenty of exhaust leakage ( under your aftercooler) –You are looking in the wrong place– Up front where the lifting eye is.

Exhaust system need to be redone– It’s “Doomed to Failure” and most likely already is leaking internally.

Tony

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