Official Cummins 6cta 450C thread

Discussion in 'Diesel Engines/Drives/Transmissions/Props' started by FeLizDream, Apr 24, 2016.

  1. CAPTAIN GREY BEARD

    CAPTAIN GREY BEARD Member

    31
    Jan 4, 2017
    Solomons Island Maryland
    SeaRay 400 sedan bridge
    Cummins 6CTA8.3
    Hey guys GREAT thread loads of info. I have 1 question though. We all seem to be cruising right around 2000-2200 RPM'S with a varying speed due to prop pitch. I get that. My question is how much fuel are you burning at cruise ???
     
  2. fwebster

    fwebster Well-Known Member TECHNICAL Contributor PLATINUM Sponsor

    Oct 6, 2006
    Middle Tennessee ; Panama City Beach, FL
    1996 450DA
    3116 Caterpillars
    Sorry guys, my mistake. I glanced at the photo on my phone and it sure looked like an after cooler. I will try to delete my previous post............
     
  3. ZZ13

    ZZ13 Well-Known Member GOLD Sponsor

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    I normally had my oil level around 2/3 up the hash marks and never had much oil blow into the aftercooler. Last oil change I filled it to the full mark on the starboard and proceeded to get oil mist blown into the aftercooler fins. Started worrying the turbo seals or air seps were at fault. Then saw Marks post, and pumped out some oil to get it back down to about 1/2 up the hash marks. Problem went away. So this oil changed I followed the full filter plus 3.5 gallons approach.


    Sent from my iPhone using Tapatalk
     
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  4. Joel_MD

    Joel_MD Member

    200
    Jun 20, 2016
    Chesapeake Bay
    390 Motor Yacht, 2005
    Cummins 480 CE
    On my boat, 2,250 RPM gives me about 21-22 knots at about 32 GPH.
     
  5. Jmwarren

    Jmwarren Member

    414
    Jul 14, 2011
    Ontario
    390 Motor Yacht
    Cummins - 480CEs
    FYI, you're a little over propped. The fuel curve for the 450c has it at 13.6 GPH @ 2200.
     
  6. Woody

    Woody Well-Known Member PLATINUM Sponsor

    Nov 20, 2007
    N. Wisconsin/Lk Superior
    2005 420DA
    Cummins 6CTA8.3
    Recently my port engine has taken to running just under 180F, it normally runs just over 160F, this at 2150rpm. If I bump the rpm up I can make the temperature climb, back it down and the temp comes right back down.

    The aftercooler, gear cooler and heat exchanger were inspected and cleaned in June, about 25 engine hours ago and impellers were change about the same time. Belt and automatic tensioner look good, I don't think there is a slippage problem.

    I've never looked at the fuel cooler, should have when things were half apart in June, but didn't. How is that built? It must not have small tubes because very large impeller pieces get through to the aftercooler.

    Looking in my Cummins Operators Manual I see a reference to the 'lubricating oil thermostat' which they also call the 'oil cooler bypass valve'. How does that work? Can it contribute to overheating?

    Strainer is clean. I opened the seacock while the top was open and water came bubbling up like normal. Exhaust water looks the same to me also.

    I'm certain the thermostats have never been changed and have some on order. Any thoughts,suggestions, are welcome.
     
  7. ZZ13

    ZZ13 Well-Known Member GOLD Sponsor

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    Woody, my fuel cooler appears to be just a double wall pipe. Water side is the inside pipe and is about 80-90% of the total pipe diameter. So that's why impeller pieces make it to the after cooler.

    A fellow 400DB owner with our engines had a similar problem on his port engine. Turned out to be the original seawater pump got old and broken down and was leaking so much seawater out that it couldn't keep up with the water volume needed at cruise. He replaced the seawater pump and he was back down to 160 degrees at cruise.
     
  8. Jaybeaux

    Jaybeaux Active Member SILVER Sponsor

    181
    Jan 3, 2016
    Upper Potomac River
    420 Sundancer 2004
    Naught On Call
    Cummins 6CTA-8.3's with V-Drives
    9KW Onan Genset
    With regard to the original sea water pumps, there was a design change a few years after (I have a 2004 420), due to the fact that the seals would leak and corrode the shaft. The shafts would then fail at speed, and I was told that you can't shut them down fast enough. I purchased and installed a new Seawater Pump P1730C, paid $459 for it. Seaboard Marine also has a design for a bit more. If you still have original pumps, they are due for a change.
     
  9. whodathought

    whodathought New Member

    4
    Jul 4, 2016
    Northern California
    1999 18 Sport
    2001 400 Sedan Bridge
    4.3 V6 Alpha 1 Mercruiser
    Cummins 6cta 8.3s
    I have the exact same condition on my port engine as Woody, except mine slowly runs up to 195-200F at 2200 rpm. Like he described, it cools down to just over 160F within a minute of dropping to non-planing speed. It will run all day at 1200 rpm and not move off 160F. So far, the raw water impeller was replaced 10 hours ago, and at that time some pieces removed from the hose to the aftercooler. The aftercooler was checked and is clear, new thermostats installed, and nothing has changed the high temp behavior at all.

    My mechanic is inspecting the raw water pump this week, looking for signs of wear or leakage. Hopefully he'll find something we can fix. I'm more accustomed to doing my own work on previous boats, but they were gassers. I'm not familiar with these engines (yet) and so I'm not confident about diagnosing this issue myself. I greatly appreciate all the expertise and information being shared here.
     
  10. 1000islander

    1000islander Member

    113
    Jul 9, 2007
    1000 Islands
    420 Sundancer
    Cummins
    Did you get to the bottom of your problem? I had the same problem, Broken Thermostat.
     
  11. whodathought

    whodathought New Member

    4
    Jul 4, 2016
    Northern California
    1999 18 Sport
    2001 400 Sedan Bridge
    4.3 V6 Alpha 1 Mercruiser
    Cummins 6cta 8.3s
    My problem turned out to be broken impeller parts on the intake side of the raw water pump. My mechanic said he's never found them there before. He checked with a couple of other local mechanics who also never had seen or heard of impeller pieces in the intake side of the pump. They were skeptical, so he shared pictures with them and me. They are attached. The one picture is the collection of pieces that were found in the intake pipe and hose, and the other is a look at the intake on the water pump where the blockage was happening.

    impeller pieces 1.jpg

    water pump 2.jpg

    With that stuff out of the way, the engine now runs right above 160 degrees no matter what speed we run it. We took an 90 minute run at a consistent 2200 RPM and it sat just above 160 degrees the entire time. It was delightful running after spending a couple of months chasing the problem.
     
  12. ZZ13

    ZZ13 Well-Known Member GOLD Sponsor

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    I am trying to learn about the transmission oil coolers Sea Ray installed on the 6CTA. Does anyone know the manufacturer and part number installed? Mine is the version that has the zinc plug fitted with a hose barb to feed cooling water to the shaft seal. So there is no zinc in them. I am assuming I have the original factory install still on the engines. I do clean them regularly. Do they have a limited life? Should they be automatically replaced at some interval (kinda like gas engine risers are) regardless of how they are performing? If I were to just replace them, what would I replace them with (manufacturer and part number)?

    That should be enough questions for now.
     
  13. ZZ13

    ZZ13 Well-Known Member GOLD Sponsor

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    Due to the overwhelming response, I did some research. First, our transmissions do not have temperature switches installed, even though our System Monitor does have an input wire ready to go for transmission overtemp. That's too bad. The ZF280A manual says the ideal operating range is 40-80 degrees Celcius with max temp at 85 degrees Celsius. This calculates to 185 degrees F. So, in the absence of a thermal warning, your notification of transmission overheat (most often due to oil cooler failure resulting in oil getting sucked out by the seawater) is the clutch plates fusing together resulting in being stuck in gear permanently (just happened to a fellow 400DB owner - so it happens).

    So every 5 year replacement sounds like a really good idea. Best I could find is options are the $700 cooler from Seaboard Marine or the $295 cooler from Mr. Cool. Interesting, the Cummins Quickserve parts list specifically lists the Mr. Cool product.

    So, now only one question left. Does anyone have any experience with the Mr. Cool transmission oil coolers?
     
  14. douglee25

    douglee25 Active Member

    Jan 13, 2008
    NJ
    Cabrio
    Volvo Drivetrain
    Why not add a temp sensor to the cooler?
     
  15. PMC

    PMC Active Member

    Apr 10, 2009
    Long Island, NY
    2001 40 Sedan Bridge
    Cummins 6CTA
    Bill I replaced my trans coolers spring of 2017, and my experience from a logevity standpoint is still limited.

    I removed my entire saltwater system for service, and noticed on the port cooler some green streeks around the solder joint....early signs of failure. The solder joint was starting to crumble, and were replaced.

    I have Mr Cool trans coolet's now....this model does have 2 zincs per cooler.
     
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  16. ZZ13

    ZZ13 Well-Known Member GOLD Sponsor

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    Thanks Paul. I think I am going to just go ahead and buy two of those. They are very easy to install. I’ve spent $600 on a lot less important stuff for the boat.
     
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  17. Jeff L

    Jeff L Member SILVER Sponsor

    48
    Aug 10, 2015
    NJ Shore
    2005 42 Sedan, Onan gen. 10' Rib dinghy w/ 6hp,
    Dual Raymarine es127, quantum radar, Evolution AP
    T 450 Cummins straight drives
    Lookin for some advice ... Performance has been in question for my 2005 42 DB / 450 HP 6CTA 8.3
    I do get 2600 WOT with a touch more on the Port .. maybe a bit less 2500 on the Stbd
    Cruise at 2200 rpm delivers 18-21 knots depending on the conditions. Average loading - (fuel & water 50% etc.)
    Current props 23 x 26 P H Cup (Michigan)

    I came across a set of Acme Props 26 x 25 P (no cup). The claim is an increase in performance w/ both speed and fuel .

    I am considering the following.
    1. Spring trial the ACME's - Achieve 2600 rpm WOT / fuel burn ?
    2. Have them downsized prior to putting on ?
    3. Any major concerns on over propping and cause of severe engine damage ?

    I wonder what others use (same boat -engine) with their 42-44 ?

    I will appreciate any feedback.
     
  18. my3sons

    my3sons Well-Known Member SILVER Sponsor

    Feb 24, 2009
    Upstate NY (lake Erie)
    2004 400DB, Onan 9 kw Gen, Highfield RIB,
    Cummins 6CTA
    If you have 100 rpm difference between the engines, something is not right. First verify your tachs with a laser photo tach. If that checks out and they both run well with no smoke, no vibration and start from cold in less than a 3 count, try checking to be sure the starboard throttle arm is going all the way forward when you pin the throttle lever at the helm, it should travel fully and just begin to load the spring.
    if that checks out, check the boost pressure at wot under load and compare the two engines. It should be a touch over 30. If the starboard is less, look into turbo issues. If the starboard is more than the port at any given cruise setting like 2250 rpm, it's over loading compared to the port, and you can assume that one of the props is out. If the laser tach confirms that the tachs are off and both engines are turning up to within a few (10 or 15) rpms of each other, under either scenario then send your props out to a good computer scan type prop shop with all of the information like what rpms each engine turns at wot under load loaded down with full fuel and water and everything else like you normally run. Keep in mind that filling up your water tank is like having 2 other couples on your boat and going for a cruise. You want these engines to turn up 2700 -2750 rpms under those conditions.
    As far as the other prop set goes, I'd forget about them, they're totally the wrong prop set to begin with. I would spend time to find out what's wrong first (if anything other than an inaccurate tach hopefully) and your over propped. Good luck.

    Edit: almost forgot, the answer to question #3 is yes, definitely. If your tachs are presently correct, you are not turning up enough rpms even with the port engine and you are running at half load.
     
    Last edited: Nov 5, 2017
  19. Jeff L

    Jeff L Member SILVER Sponsor

    48
    Aug 10, 2015
    NJ Shore
    2005 42 Sedan, Onan gen. 10' Rib dinghy w/ 6hp,
    Dual Raymarine es127, quantum radar, Evolution AP
    T 450 Cummins straight drives
    Great information. Thanks for taking the time to respond.
    I have several thing to check out.
     
  20. ZZ13

    ZZ13 Well-Known Member GOLD Sponsor

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    Regarding the gear oil coolers, we pulled the damaged zf280 transmission and the owner took it to the rebuild guy. I thought I’d post that he said gear oil coolers should be replaced every 7 years in salt water and every 8 years in fresh water. I assume most all of us with the early 2000s 450 Diamonds are still running 15+ year old oil coolers.
     

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