Official Cummins QSC-500 Thread

Discussion in 'Diesel Engines/Drives/Transmissions/Props' started by Hampton, Nov 16, 2011.

  1. Airplane Guy

    Airplane Guy New Member SILVER Sponsor

    11
    Feb 26, 2013
    Noank Ct
    2006 44 Searay Sedan bridge
    2005 Zodiac Yacht line 340, 30 hp Yamaha
    GHS hydraulic Lift
    Cummins QSC 500
    Thanks for the advice
     
  2. JV II

    JV II Active Member

    Nov 17, 2007
    Newport, RI
    2016 50 Fly
    Volvo Penta D11
    There may be more than one problem causing all this and you may have peeled away a few of them. Looking at your Racor filteres, I noticed that one of them shows dirt only on the lower half. My 48DA was doing that on one engine. The problem was air seeping into the fuel system under the Racor cover. The bowl was half empty when I checked it on one of the filter housings. It was a recurring issue and the cover was very sensitive. I needed to crank it down hard and make sure ther rim was super clean. Once the tab on the Racor handle got pinched in the gasket. It did not cause a performance problem all the time, but when it did at worst it would air lock the engine. At best, it would hesitate.
     
    Last edited: Jul 8, 2018
  3. sb in gp

    sb in gp Member

    754
    Oct 10, 2006
    Grosse Pointe, MI
    44 Sedan Bridge 2006
    Cummins QSC-500
    I change my impellers every 2 seasons during winter layup. I take the pumps off because it is easier to pull and install the impeller on the bench. My impeller kit comes with an o-ring for the pump but I’d like to replace the o-rings on the in/out pipes that connect to the pump. Can anyone tell me the part number for those o-rings?
     
  4. villain style

    villain style Well-Known Member SILVER Sponsor

    Oct 10, 2006
    Mears Point Marina Kent Island, MD
    2006 44 DA
    QSC 8.3s
    Cummins QSC 8.3s 500HO
    Boat is new to me with 950Hrs so I am doing some PM work. I am installing new belts to start with. Is there any reason that I should be changing the Idler Pulley or Tensioner also? Do they have a service schedule as well?
     
  5. bbwhitejr

    bbwhitejr Well-Known Member SILVER Sponsor

    Apr 14, 2013
    Lake Lanier GA
    2007 44DB
    Cummins QSC 8.3s
    That is the first thing I did when I got my boat as well. I had one belt that was making a little “dust.” I did not change anything but the belts, and no more dust. If you go back and read the beginning of this thread, there is a lengthy discussion around the belts. I keep one new one and the best one of the two I changed out as spares. It appears that Cummins’ are notorious for going through belts.

    Bennett
     
    villain style likes this.
  6. villain style

    villain style Well-Known Member SILVER Sponsor

    Oct 10, 2006
    Mears Point Marina Kent Island, MD
    2006 44 DA
    QSC 8.3s
    Cummins QSC 8.3s 500HO
    Does anyone have P/N for Thermostats and gasket? I also heard there were two thermostats per engine. Is that true? if so are they the same? Thanks..
     
  7. Jaybeaux

    Jaybeaux Active Member SILVER Sponsor

    331
    Jan 3, 2016
    Upper Potomac River
    420 Sundancer 2004
    Naught On Call
    Cummins 6CTA-8.3's with V-Drives
    9KW Onan Genset
    villain style...re belt tensioner.....if it looks like this, change it! 20170916_123412.jpg
     
    villain style likes this.
  8. swaterhouse

    swaterhouse Active Member

    385
    Jan 7, 2015
    Mattapoisett, MA
    2007 Sundancer 44
    Cummins QSC 8.3
    Thermostat 3972537
    Gasket (need 2) 145581

    You may also want o-ring 145582, it's between the pipe and heat exchanger, you need to remove that pipe to get to the thermostat.

    There is only one thermostat per engine.


    You can register at https://quickserve.cummins.com with one or both of your engine serial numbers, from there you get all the parts diagrams, manuals etc.
     
    importmonkey and villain style like this.
  9. villain style

    villain style Well-Known Member SILVER Sponsor

    Oct 10, 2006
    Mears Point Marina Kent Island, MD
    2006 44 DA
    QSC 8.3s
    Cummins QSC 8.3s 500HO
    Thank you - I am on Quickserve.cummins but I cannot get to any parts diagrams. I'll look again. Thank you for the response..
     
  10. swaterhouse

    swaterhouse Active Member

    385
    Jan 7, 2015
    Mattapoisett, MA
    2007 Sundancer 44
    Cummins QSC 8.3
    I assume all regions have the same pages but maybe not.

    In pic below, select one of your ESN's on the left, then above that click Parts.

    Once on the parts view, make sure you select "Display Upfits" to show the marinized portions of the engine that were supplied from the factory (which for Sea ray was everything painted white and attached to engine).

    Untitled.png
     
    villain style likes this.
  11. Robski97

    Robski97 Well-Known Member

    Jan 15, 2007
    North Bellmore, NY
    44DA
    Cummins QSC 8.3's
    Anyone have a drain pan gasket leak. I have two leaks .. Mutiple drain pan gasket leaks and one leak on the back side of the motor. ( where the belt is which is the front normally ) Its the bottom right corner... Looks like a train wreck to replace both gaskets ….

    Rob
     
  12. bajturner

    bajturner Member GOLD Sponsor

    531
    Aug 17, 2010
    Ottawa, Ontario, Canada
    2008 44 Sedan Bridge
    Avon 380DL RIB w/ Yamaha 40
    Highfield CL290 RIB w/ Tohatsu 9.8
    Twin QSC-500 HO
    So, here is the latest update, and I am hoping the lower-half dirty filter combined with something else I found are the cause and an indicator of the root cause (could I be that lucky?).

    The stumbling problem persisted on and off, along with a bit of light gray smoke from time to time, and I became convinced there was an issue with the port low pressure fuel pump. I decided to trace the fuel line from the tank to the engine to see what else could possibly be restricting fuel flow.

    At the very start of my tracing, I found this:
    upload_2018-7-23_20-59-8.png

    A kink in the fuel line between the tank and the Racor. I also noticed there appears to be an old screw hole where perhaps the retaining clamp used to be originally.

    I wonder why the original owner would have repositioned this.

    I changed the positioning, removing the kink, and the problem has been gone ever since.

    Could this simple issue possibly have been the cause?
     
    techmitch likes this.
  13. Tman

    Tman Member

    284
    Aug 10, 2012
    Seattle, WA
    2014 Sabre 48 Salon Express
    Twin Cummins QSC 550
    Zeus Pod Drives
    Anything restricting fuel flow is problematic. Nice work in tracking this one down. Much frustration along the way I’m sure but whoever said boating is always stress and frustration free? Nice going and hope that is your gremlin.
     
  14. JV II

    JV II Active Member

    Nov 17, 2007
    Newport, RI
    2016 50 Fly
    Volvo Penta D11
    Unbelievable. You found it.
     
  15. bajturner

    bajturner Member GOLD Sponsor

    531
    Aug 17, 2010
    Ottawa, Ontario, Canada
    2008 44 Sedan Bridge
    Avon 380DL RIB w/ Yamaha 40
    Highfield CL290 RIB w/ Tohatsu 9.8
    Twin QSC-500 HO
    I did. I felt like the smartest guy on the lake!!

    Turns out it was part of the problem, and likely the cause of another. Somewhere else on this site, maybe this thread, someone mentioned replacing the lift pump (sometimes called the primer pump) before doing any other expensive repairs. Good advice.

    In my case, after correcting the kink the problem went away for about 4 hours of running time until very similar behaviour returned. This time I also noticed the port pump did not run at ignition on so at least there was a definite, easily-identifiable problem.

    I had a Cummins tech make the trek to my marina to replace the pump and go over the engine completely. Short story is the pump had failed and once replaced all fuel pressures were correct and the engine ran perfectly. I hope that continues to be the case! The hypothesis is that the kinked line stressed the pump and/or caused it to overheat over the years and reduced its performance. The tech was actually able to get it going again, but intermittently. And when it was running, it didn't output very much pressure. This would cause the behaviour I was experiencing.

    The tech found no other issues. He also upgraded the ECMs on both engines as they were 4 revisions behind. He didn't think this would result in any noticeable change, however, based on the change history.

    There was some additional interesting learning that came with replacing this pump.

    I found the document at the link below and used it to educate myself about the fuel system on these engines. There is one major difference between the system described in the slides and the system actually used in the Sea Ray application, however. The ECM cooler plates on my engines are not used. The cooler plate fuel channel has plugs in it (apparently from the factory, complete with white paint) and there is no check valve since it isn't needed.

    One other major difference is the pump that was failed, described as a prime pump, lift pump, or fuel transfer pump depending on where you are reading, does not apparently run only at start-up, but also during normal operation. This is not the case in a truck or generator application, according to the tech (he said the vast majority of the repairs he does to QSCs are generator applications). I assume this is why the pump is described in different ways.

    At 750rpm idle, fuel pressure downstream of this pump was -5psi (vacuum) with the old, failed pump (and also with the new pump when disconnected), and 22 to 25psi with the new pump when connected). We could reproduce the stumbling by unplugging the power to the new pump, and also view the pressure drop on the tech's gauge.

    Referenced document: https://www.scribd.com/document/381847905/Common-Rail-Fuel-System-CM850-QSC-and-QSL

    In a strange way this problem was beneficial for me. With this being my first season with this boat, and my first diesel boat, I knew next to nothing about the engines or fuel system. I now feel I have a decent basic understanding and know where to start looking should another problem arise. That said, I would be ok with not learning anything else for a while!!
     
  16. bajturner

    bajturner Member GOLD Sponsor

    531
    Aug 17, 2010
    Ottawa, Ontario, Canada
    2008 44 Sedan Bridge
    Avon 380DL RIB w/ Yamaha 40
    Highfield CL290 RIB w/ Tohatsu 9.8
    Twin QSC-500 HO
    A question for all you experienced diesel owners...

    Do you carry a jerry can of diesel on board in case you ever need to change the Racor filters and top them up while away from the dock?

    I have been keeping a can in the bilge, but I would rather not. I know it is supposed to be safe on a diesel boat, but it just feels wrong! It also takes up space and is a nuisance to manage to keep from becoming stale / fouled.

    In a pinch, could the old filters be pulled out the top and a fresh one popped in without draining and refilling the Racor? I know there would be a small air gap at the top due to the old filter taking some fuel with it, but would this be a big deal temporarily until getting back to a dock?

    It looks like the output from the filter is located such that a small air gap at the top shouldn't necessarily cause any air to be introduced.
     
  17. importmonkey

    importmonkey Opinionated Member

    939
    Jul 9, 2015
    Middle River, MD
    2007 44 Sundancer
    QSC 500s
    I can see the logic, but I wouldn't want to do that out at sea. I'd limp back to port where I'd hopefully be able to get diesel if needed. I'm sure the big guns will chime in with better advice.
     
  18. bbwhitejr

    bbwhitejr Well-Known Member SILVER Sponsor

    Apr 14, 2013
    Lake Lanier GA
    2007 44DB
    Cummins QSC 8.3s
    Not a big gun and likely not better advice, but I do carry a 2.5 gal jug of diesel. It has about 2 gal in it.

    Bennett
     
  19. swaterhouse

    swaterhouse Active Member

    385
    Jan 7, 2015
    Mattapoisett, MA
    2007 Sundancer 44
    Cummins QSC 8.3
    I carry a 2 gallon jug of deisel in the engine room. I dump it in the tank at the last fill up before winter layup and fill in spring with fresh fuel and use some for my filter change.

    In an appropriate can well secured, I see no issue with storing there.

    Limping in could be more dangerous than replacing filters at sea. Twin boats are hard to control with only one engine.
     
  20. importmonkey

    importmonkey Opinionated Member

    939
    Jul 9, 2015
    Middle River, MD
    2007 44 Sundancer
    QSC 500s
    Huh. Learn something everyday.
     
    Mjresq4 likes this.

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