Cummins Marine Diesel Repower Specialists › Forums › Cummins Marine Engines › 2011 Cummins QSC 490

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  • October 21, 2021 at 5:32 am #122183

    Kane Bounds
    Participant
    Vessel Name: Fish Bound
    Engines: QSB 5.9 355
    Location: Ocean city MD
    Country: United States

    {content}Recently purchased a new to me Charter/Passenger boat with a QSC 490 4200 hours. Looks to be the original smart craft gauges. Not the same Vessel View 4 I have on my 2018 QSB 5.9 355.
    On sea trial with 5 people, and full fuel we weā€™re able to hit 2570, but engine was only showing 92 percent load.
    Iā€™m in the process now of getting everything ready for when I begin to use the boat starting next April
    Aftercooler has bubbling on the bottom aluminum casting, so I just replaced that with a new one. I did manage to get old one apart, no signs of salt on core, and not much sludge.
    My question is just sent prop off to get reconditioned. Should I take a inch of pitch out, or leave it the same? Not sure why I could only hit 2570, but showing 90 percent load. 2220
    Was 65 percent load. Any help would be appreciated. Engine has 4200 hrs, and the boat is a 38×14 Evans

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  • October 29, 2021 at 9:33 am #122421

    Steve Lewis
    Participant
    Vessel Name: Just Us
    Engines: Cummins 480CE
    Location: Marblehead, OH
    Country: USA

    Kane,

    If you look at the Performance report that Tony attached you see that the 490 is rated at 2500 RPM with the gov kicking in somewhere in the 2565 to 2585 range to limit RPM. You can also look at the data plate that is on the engine and it will tell you the rated RPM. You reported 2570 which is spot on. Since you are seeing a load% that is below 100% at 2570 that bodes well for the life of the engine as it pertains to prop loading. Just keep up on the preventive maint as per the “Seaboard Way” and you should get some good life out of these engines.

    Tony mentioned that the 490 is a detuned 540 which is a beast in its own right. Good that you replaced the Aftercooler and then looked at the old one. Have the old one serviced and pressure tested. You might have a rather nice spare part that can be used in a pinch.

    October 29, 2021 at 5:44 am #122412

    Kane Bounds
    Participant
    Vessel Name: Fish Bound
    Engines: QSB 5.9 355
    Location: Ocean city MD
    Country: United States

    Thanks Tony appreciate you taking time from your busy schedule to answer my questions.
    Is the 2011 QSC 490 a 2500 rpm or2600 rpm engine? I did put a brand new aftercooler on it after running it to the yard. Old one had bubbling on bottom of the housing. So I figured it was shot.
    Took my time and was able to get old cooler apart, no signs of salt and minimum sludge

    Thanks
    Kane

    October 29, 2021 at 5:35 am #122409

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    QSC 490 CPL 8017

    Looks to me like you are propped right.. Engine is making the governor and you have some power to spare.. Nothing wrong with that ( IMO, actually everything is right with that), and as long as you are happy with the speed of the vessel in the 1900-2300 RPM range, then don’t mess with the props..

    Performance curve attached.. It’s a 2500 RPM rated engine, de-rated from the 540 version..

    What I’d worry about are the insides of your aftercooler.. It could easily have 15 yrs of marine age on it.. If a saltwater boat since new and was not flushed religiously, then your aftercooler is Priority 1

    As to propping in general, my own boat with a newer QSB 6.7 550 is propped to about 80% at WOT.. I cruise at 2800-3000 in good weather……………..Totally cool with me..

    October 28, 2021 at 6:13 pm #122401

    Kane Bounds
    Participant
    Vessel Name: Fish Bound
    Engines: QSB 5.9 355
    Location: Ocean city MD
    Country: United States

    I never did no load it. Was just wondering if anyone else is around 65 percent load at 2200.

    Thanks

    October 28, 2021 at 5:51 pm #122400

    Luke Nelson
    Participant
    Vessel Name: Southern Image
    Engines: QSC 8.3 540hp
    Location: Perth
    Country: Western Australia

    On 2nd look this may be a 2500rpm fuel curve and a 2585 max over speed rating.

    October 26, 2021 at 5:16 pm #122342

    Luke Nelson
    Participant
    Vessel Name: Southern Image
    Engines: QSC 8.3 540hp
    Location: Perth
    Country: Western Australia

    Isn’t the engine only meant to get 2600rpm?
    Do you get 2600 on flight rev in idle?

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