Time for some QSM11 education. As you read thru the below, always associate or think thisāItās 20 HP per gallon per hourāexample = burn 17.5 GPH = 350 HP that is being asked from the engine – and that is not RPM dependent. So at a full load of 580 HP, the engine would burn about 29-30 GPH.
Itās 20 HP per gallon, per hour
Read below for some solid bullet points regarding the Cummins Marine QSM11 Marine Diesel Engine:
1) The base engine was developed in the mid-90ās and really came from the L10 (late 80ās thru mid-90ās). It was a 100% solid truck platform FROM DAY ONEā¦ā¦ā¦.
2) First āmarinizedā version was released in 1999 in both 635HP and 580HP (both 2300 rated RPM) versions. Seaboard sold and installed the 1st set on the West Coast and put them in the APOLLO out of San Diego in the Spring of 2000. I tracked those engines until J.J. sold the vessel about 8 years ago and, at that time they were well over 50,000 hours each (no rebuilds at that time) ā Very solid engine ā he ran easy (maybe averaged 10-12 GPH per engine cruising at 10-11Kās).
3) In our personal opinion, the initial marinization (and IMO, current marinization) of the engine proved to be very weakāCummins engineers decided for ??? reasons (cost, emissions, weight, compactness, time to develop, āperceived efficiencyā, etc, etc.) to keep the dry truck manifold and dry turbo and IMO, was a very poor choiceā¦.. J.J.ās engine did not even make 500 hours before we had to warranty the manifolds. HENCE, the DRY QSM was born and I gave it that name and has stayed with it until today.
4) Within a year or so, Cummins released some new HP ratings for the engineā350 at 1800 RPM, & 400, 450 (at a 2100 RPM rating) and 535 at 2300 RPM. Still setup as āDRYā versions and all suffered the same issues (warped manifolds, broken exhaust studs, warped or cracked turbo bases, etc) but to a much lesser degree as the MAX HP was less. Some engines would survive for a few 1000 hours before they had an issue, yet others would not make 500 hours before exhaust āleaksā were present. It basically came down to How much HP you extracted from the engine at CRUISEā¦ā¦ā¦ If you traveled at or above 16-17GPH and you did it at RPMs less than 1800, then you were going to have problems. Travel at 17GPH at 2000 or above and the manifolds held up pretty good. So two things became apparent over the years: One was the engine could make the power, but the manifold & turbo did not hold up at higher loads. And if you needed to pull 400HP from the engine for cruising, better prop the engine to do it at RPMās above 2100 if you want any service from those parts. BTW, to this day itās all the same, but maybe worse as the 670 version really wears them out fast, especially the manifolds. Go to some other forums and type āDRY QSMā or āQSM11 manifold leaksā.
5) Enter the āWET QSM 11ā (Another term I made up and has stuck to today) ——————Sometime about 2005 Cummins released a WET version of the QSM11āIt came from the generator group and overall was engineered very wellāOr should I say, āreverse engineeredā.. What that team of engineers did was take āoff the shelfā components (the 6CTA 8.3 450 Diamond aftercooler and heat exchangerāboth proven components) and built a well engineered wet exhaust manifold, and adapted those components to the QSM 11.. IMO, they did a 99% job (I can always find room for improvement) ..The engine met EPA Tier 2 specs and had HP ratings of 350 @ 1800 (right from the generator rating), 400 and 450 at 2100 RPMā¦ā¦ā¦ā¦.IMO, that engine turned out to be the best marine engine Cummins had released to date in that size rangeā¦ā¦ā¦ā¦ā¦ā¦ā¦ā¦ā¦Installed a bunch and one pair is in SD now (Ventura IIāclose to a 200 ton fishing vessel) and Iām sure it is over 50,000 hrs — ROCK Solid.
6) Fast forward to about 2013-ish————As the population grew and āsuper good feedbackā continued, a āBlack Eyeā suddenly popped up about 5 years ago. I had installed about 10 of these engines in the Long Beach and San Diego area over a 2 year period. All of a sudden, engines were ādropping valvesā in the 2000-4000 hours range. Fingers started pointing immediately (bad install — āTony did somethingā (I was a common denominator at that time), lack of maintenance, etc etc etc)ā¦ā¦ā¦ā¦. Over the next & very difficult 6-8 months, all sorts of testing went on to figure out what is wasāThe Cummins factory were working on it too, but kept very quietāIn fact, during the interim āfinger pointing period,ā they re-wrote the oil change interval to less than 50% of before (only the Marine versionānot the truck engine). To me that said one thingāThe marine engines were being built in a different location and there was QC āoil lubricationā issueāOf course nothing was saidāAlso during this period, other QSM 11 engines from this general production period popped (same valve issue) in other areas of the country (that took me out of the equation)ā¦ā¦ā¦ā¦ā¦ā¦Then, maybe after 2 yrs or so, all of the issues disappeared and the oil change interval went back to normalā¦. This is what I feel happenedāThe oil feed to the top end was at less than 50% of normal caused by improper cam bearing assembly that would block the oil flow to the overhead valve gear.. This caused the rocker arm pads to wear very quickly and then they hit the valve keepers. The keepers would pop out, and the rest was historyāLots of in-house documentation on thisā¦ā¦ā¦ā¦But long story short, other than this one glitch, the engine is back in favor with me as a True Marine Commercial Heavy Duty 11L engine that IMO, will never wear out in a 1000 hour a year application. Plus the electronics are 100% and have never needed any upgradesāToday this engine is EPA Tier 3 and last year was released at 400HP, 100% continuous duty at 1800 RPM. That is a serious rating for an 11L engine, and proves without any doubt that Cummins is proud of the āinternalsā that are really the basics of the engine…..
7) Let’s take a look at the T3 QSM11 rated at 450 HP / 2100 RPMā¦. Set up right, they can burn 20 GPH making 400HP 24-7-365 and never look back.. Youāll have an extra 50 HP per engine that you can use to 2-3 hours at a time, and again, the engine will never have a hiccupā¦Run hard 50-60% of the time, and youāll see 20,000+ hours out of this engine before a top-end.. It will run easy at 30% duty cycle (meaning cruising at 12K or less), and youāll go 70,000 hours + before top endā¦So there it is.. Now you know all about this engine.
Just so you know, the QSL9 rated at 450 HP 2100 RPM (medium continuous duty) would also do an operator right in a similar application, and would be lighter, quieter, smoother, and less expensive to buy & maintain. Another really great engine for high hour commercial applications that I think is in a class of its own.
But neither of these engines will give you the āShow & Tellā day “speeds” like you would get with the 715 Version.. Also, of āworthy mentionāā100% of all the internal parts ( the āgutsā so to say) of any of these versions (cranks, bearings, pistons, rods, seals, heads, valve gears, etc etc etc etc) are identicalāOnly the engineās āhang-onsā and ECM coding are different.
Now ask yourself which engine will last longer running at 10 GPH, 15 GPH, or 20 GPMā¦