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    • Cummins Marine Forum Topics
    • QSB 6.7 Crank Case Pressure

      This topic has 2 replies, has 2 voices, and was last updated byJoe F 1 year ago

      March 21, 2023 at 11:08 am A recent pre-sale engine survey on a family member’s boat indicated: BLOW BY TEST:<br />Crankcase blow by test was performed using a Cummins Insite program and<br />laptop computer. Port CCP was 5.7 InH20, which is above average and<br />starboard was 4.4 which is also above average. The engines are 2014 (330 hrs) Qsb 6.7 480hp. Engines run good, no smoke, no oil leaks. Turbos intake side appear OK. What should be conside…

      Started by: Joe F in: Cummins Marine Engines


      2 Replies
      March 23, 2023 at 11:47 am Thanks Tony for the response- we won’t worry about the CCP. Aftercooler housings were no good in 2018 and replaced with new and greased. We added freshwater flush at that time.  Just pulled the cores after five years and they came apart easily and look serviceable, pics attached.  Joe

      Last Post by: Joe F posted: 1 year ago

    • QSB 6.7 Aftercooler Service-RTV?

      This topic has 4 replies, has 4 voices, and was last updated byJoe F 5 years ago

      October 17, 2018 at 11:47 am We asked a Cummins tech to service the aftercoolers on QSB 6.7s and reinstall with Alco Metalube per the guidance on this site. The tech recommends Cummins PN3164067 (Loctite 5699 Grey RTV silicone sealant) to seal between the brass endcaps and aluminum housing ( to better fill any pitting), with the Metalube on the bolts. Is this an appropriate use for the RTV or should we insist on the Metalube? Coolers haven’t been pulled yet so condit…

      Started by: Joe F in: Cummins Marine Engines


      4 Replies
      October 18, 2018 at 8:12 am Got it, thanks all. Joe

      Last Post by: Joe F posted: 5 years ago

    • QSB 6.7 Re-Rating 480 to 550

      This topic has 5 replies, has 3 voices, and was last updated byTony Athens 5 years ago

      October 2, 2018 at 2:12 pm Hello All, I’m helping a family member in Florida with his boat, a recreational sportfisher with twin QSB 6.7 480HP@3300 (CPL 4191) with ZF 2800 series pods. New it turned 3350 at WOT. Now, with added gear, dirtier bottom, etc it is operating above the Cummins prop demand curve at cruise and only reaching ~3200 WOT. One option is to change props ($$ x 4). Is it feasible to change motor to the intermittent duty rating of 480HP@3000 RPM or HO of …

      Started by: Joe F in: Cummins Marine Engines


      5 Replies
      October 6, 2018 at 7:12 am Steve, I think you are over thinking this, or maybe you are thinking this way ?? Yes—all of the CPL4191’s are the same engine internally so put them all on a dyno at 15 GPH @ 2600 RPM and they will all “wear out” at the same rate.. IMO, the prop curve fuel burn has nothing to do with it………..But with that said, (another IMO), in general, the higher RPM you pull that HP at (ABOUT 300HP) , the easier it is on the engine ( like on the 3300 RPM v…

      Last Post by: Tony Athens posted: 5 years ago

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