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Old 06-25-2019, 11:44 AM   #1
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Dry QSM11s

We are looking at boats with these engines. Should I be afraid? ANd what am I looking for as it relates to blown exhaust gaskets or cracked manifolds? I know my way around diesel engines but not sure where to look for the failure points...the coolant tank seems to block the ability to truly inspect the condition. I did take some pics. Not sure what I am looking at although I do see what could be considered soot. This engine only had 425 hours on it and rated at 616hp.

How difficult is it to change gaskets or repair replace manifolds and how expensive would it be to hire it out? Just wondering if it is a deal killer and/or a fatal flaw. I do know these engines can be run to prevent this from happening. Sadly most people are unaware.
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Old 06-25-2019, 11:45 AM   #2
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Old 06-25-2019, 12:06 PM   #3
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It is a pain to get in there to access the dry manifold. If you have good access to right hand side, it is not too bad, just a lot of stuff to take off.

I do see some soot there, so there may be a little leak.

In general the exhaust manifold becomes a problem mostly on engines that run overloaded, over propped, dirty bottom.

Want it propped to get 2360rpm+ on the pins, or about 90-95% load at 2300. And then cruise at under 20gph.

Other than that issue, it is a nice engine. Gets a true 20hp per gph in the 1700-1900rpm cruise range along prop curve.
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Old 06-25-2019, 12:21 PM   #4
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It is a pain to get in there to access the dry manifold. If you have good access to right hand side, it is not too bad, just a lot of stuff to take off.

I do see some soot there, so there may be a little leak.

In general the exhaust manifold becomes a problem mostly on engines that run overloaded, over propped, dirty bottom.

Want it propped to get 2360rpm+ on the pins, or about 90-95% load at 2300. And then cruise at under 20gph.

Other than that issue, it is a nice engine. Gets a true 20hp per gph in the 1700-1900rpm cruise range along prop curve.
I think Tony says to underprop them so they spin a little faster at lower load. I think the idea is to keep the air moving through them a little quicker. SO instead of that 1700-1900 range, I think he wants 2100 at the same theoretical load. I may be wrong though. The first thing I need to find is a boat without already having the issue.
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Old 06-25-2019, 01:22 PM   #5
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Yea, better to underprop. By how much is debatable.

EGT gauge is good stuff on these.

And it won't turn any higher than I think 2380, the electronic governor has a narrow range between full load and high idle.

Rather than worry about full power rpm, just set it at 2300 exact and read %load. At 90% there you are good.

What kind of boat? Single engine?
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Old 06-25-2019, 01:31 PM   #6
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Yea, better to underprop. By how much is debatable.

EGT gauge is good stuff on these.

And it won't turn any higher than I think 2380, the electronic governor has a narrow range between full load and high idle.

Rather than worry about full power rpm, just set it at 2300 exact and read %load. At 90% there you are good.

What kind of boat? Single engine?
No...twins. Sea Ray Sedan Bridge 480. The older ones have Cat 3196s...which you probably know have a storied past with aftercoolers and stuff. What is your take on the 3196s? I have stayed away from them.
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Old 06-25-2019, 03:25 PM   #7
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I don't have much experience with the 3196. Some. I know they went through some design changes on the aftercooler, some apparently leaked. I more suspect the issue is condensation, and with the high mounted location of the aftercooler, condensation drips could go into the air intake. They put gutters and drain valves in the bottom of the clam shell housing, but if one valve got stuck, you've got a wet engine.

The QSM11 has a low mounted cooler with the outlet on the top, no such problem there.

If a 3196 passes inspection, I would not be too afraid of it. Also a very nice running engine.

I recommend anyone with high output TA diesels to run at no wake speed for like a half hour to let charge air dry out the aftercooler. Especially if boat is going to sit afterward for weeks+. Getting under way the next morning, no big deal.
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Old 06-25-2019, 04:45 PM   #8
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I recommend anyone with high output TA diesels to run at no wake speed for like a half hour to let charge air dry out the aftercooler. Especially if boat is going to sit afterward for weeks+. Getting under way the next morning, no big deal.
That is a very interesting suggestion. I guess I do it by default as it taeks my engine FOREVER to warm up. Maybe not 30 minutes but a solid 20. And I don't throttle up until the engines are warm. But that is a good recommendation and the first time I have heard of it!
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Old 06-25-2019, 04:54 PM   #9
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I should have clarified- Running slow recommended before shutdown, after running hard where condensation occurs.

Warm up also important, but nothing wrong with cranking it, throwing lines and running hull speed to warm up. It heats up quicker that way, but not as much thermal stress as hammering a cold (or cool) engine. No fan of idling to get warm up, but sounds like that is not what you do.
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Old 06-25-2019, 05:06 PM   #10
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I should have clarified- Running slow recommended before shutdown, after running hard where condensation occurs.

Warm up also important, but nothing wrong with cranking it, throwing lines and running hull speed to warm up. It heats up quicker that way, but not as much thermal stress as hammering a cold (or cool) engine. No fan of idling to get warm up, but sounds like that is not what you do.
Yep...always run slow before shutdown. Hell we have to do that in the airplane for the same reasons. But I do run at about 1300RPM on warm up. I do not idle to warm up. I start and go!
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Old 06-25-2019, 07:20 PM   #11
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Wendy will love the new boat.

I have QSM11s in my boat, 715 hp. 1300 hrs no problems yet.

See you in Ft. Pierce.
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Old 06-26-2019, 08:14 AM   #12
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I always like to run my diesels, truck and boat, easy until coolant temp reaches 140 to 160 F before I load it up.
I have a 20 minute idle to 1100 rpm to the sound from my marina, so that is no issue.
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Old 06-26-2019, 09:38 AM   #13
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A few years ago I was looking at a vessel that had the Cummins NT855 dry exhaust manifold. In communications with Tony he requested his usual ( and very smart) group of clear and in focus high resolution pictures. This I did and quite shortly he returned the pictures with numerous red circles as to where there were leaks. He also suggested the white glove test in the ER. This I did and was shocked as to soot amounts that showed up.

Tomas on boat diesel is also a great source of information on the Cummins dry exhaust manifolds. My take on the whole subject is if they are leaking now, they will not get better.. Your tolerance for a sooty boat and ER interior is the determining factor IMHO.
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Old 06-26-2019, 09:54 AM   #14
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I have got to say after having 871s, soot is better than oil.
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