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Considering Repowering Again

Discussion in 'Technical Discussion' started by DOCKMASTER, Jul 24, 2019.

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  1. DOCKMASTER

    DOCKMASTER Member

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    Back in 2015 I considered Repowering my 54' Donzi Sportfish when I had a failure with the existing STBD Detriot 12V92TTA. For various reasons I decided back then to rebuild the Detriot. The rebuild was successful and both engines have been operating well the last four years (knock wood).
    Despite the engines running well I continue to have the itch to Repower. When I bought this boat in 2012 I loved everything except the Detriots. Today, I love the boat even more as we have continually upgraded and improved the boat every year. Although the engines run well I am fearful of issues as it is difficult to find people still working on Detriots. Further, the DDEC system is near impossible to service and find parts other than getting lucky from Sturdy or Ebay.
    One of the reasons I didn't Repower is when I considered it previously I really wanted to increase HP and that was a major undertaking. Fast forward to today and I'm realizing life is sometimes better without needing to go faster. In fact, I go much slower often now. So now I'm exploring Repower with the 1150 hp CAT C-18 ACERT engines and ZF Trans.
    I'm confused if my existing Detriots are 1150hp or 1080 hp. There is conflicting info. I can find documentation on the 1080hp but coming up empty on 1150 hp 12v92TTA. Anyone shed some light here?
    Everything I read on the C-18's is pretty positive. They are about 800 lbs lighter than the Detriots and I would be able to get rid of all kinds of additional stuff like remote trolling valve actuators with cables, lots of electrical wiring, additional 12v batteries and chargers just to run the 12v DDEC stuff, etc, etc. I bet I would easily shed 2,000 lbs off the boat.
    So my thinking is if I can stay at the same HP, keep the existing shafts and struts yet shed some weight it seems like I should maintain current cruising speeds and burn a little less fuel. Who knows, maybe even pick up a little speed. I'm also hoping the CATs would be a little less noisy at cruising speeds??
    I'm pretty set on CATs as I can get them serviced and find parts easily. The C-18s occupy less space than my existing engines so servicing should be a bit easier. I would go with C-32s in a hearbeat but I just don't think they will fit.
    Any input or suggestions? Anything else I should consider?
  2. Capt Ralph

    Capt Ralph Senior Member

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    The different DDC HP numbers are SAE flywheel HP and propeller shaft HP.
    It's the same engine.
    IMO, the C32s will fit. In a lower HP config & tune, could also near last forever.
  3. olderboater

    olderboater Senior Member

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    That would surprise me.
  4. DOCKMASTER

    DOCKMASTER Member

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    Capt Ralph can you expand on your opinion the C32s will fit please? My research shows the C32's at 9" taller and about 10" wider. The Detriots already push the limits of my engine room. I couldn't get a length with gear to compare to but just the added height and width seems like it would be problematic. What am I misisng?
  5. Capt Ralph

    Capt Ralph Senior Member

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    Time to crawl in with a c32 (or 3412) somewhere with measuring tape in hand. Having worked around both engines with out a tape in hand, IMO the low profile 12V92TA and straight ZF clutch was still taller.
    The DDC blowers protrude up from the airbox about the same as Cats aftercooler.
    Take a C-32 with a down angle propeller shaft and I think you could lay a bunk above it for the in-laws.
    Less the oil filters, fuel filters, black boxes and junk that can be remotely mounted, both blocks and exhaust manifolds are about the same width,, IMO with out a tape in my hand..

    The DDCs could not use a down angle clutch because of all the junk on the block sides below the exhaust manifolds. The Cat just has a starter down there.

    The Cat heat exchanger does eat up some room. No reason it could not be lowered some. Down angle clutch will really help here also.
  6. DOCKMASTER

    DOCKMASTER Member

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    Thanks. I do have 10 degree down angle gears behind the 12v92s now. I'll have to look closer at the C-32s and possible remote mounting of items.
  7. Capt Ralph

    Capt Ralph Senior Member

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    You have turbo, blowers, more cam shafts than Carter has pills and inter gears wizzing all over those DDC engines. Plus, because of the open exhaust for the Detroits, near wide open exhaust. Then old freaking motor mounts. No telling where your noise is coming from now.
    IMO (again), with some work, maybe a muffler upgrade, you should be quieter.
  8. Capt Ralph

    Capt Ralph Senior Member

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    I'm sorry your at the far corner of the country from me.
    I luv working on these projects. A few under my belt. None this large, but all fun and working very well.
  9. DOCKMASTER

    DOCKMASTER Member

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    Well fortunately I'm in the shipyard business so lots of resources at my disposal. However, we are large commercial, not yacht so a bit different.
  10. PacBlue

    PacBlue Senior Member

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    The CAT C18 engines are known to be noisier than the rest, that particular model only. Even with a good Marine Exhaust or Centek muffler system. But your DD’s were not quiet engines so it may be a wash.

    The other alternative is the derated MTU 10V2000M86, probably the best package/power for the Donzi 54 , would have a higher upside on resale too.
  11. Capt Ralph

    Capt Ralph Senior Member

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    I remember working with a pair of C32-1652s in a Hat 72. I did not think it was that loud.
    Muffler to below hull outlet. Idle bleeder out the stern.
  12. PacBlue

    PacBlue Senior Member

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    It’s the straight inline C18 that is the loud one, common knowledge on the SF circuit. Unique sound because of its firing order.

    But again , the 2-stroke Detroit’s have their own bark.
  13. Beau

    Beau Senior Member

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    Mans will just hum...a bit more expensive, but I think everyone will agree that its a very quiet motor.
  14. Capt J

    Capt J Senior Member

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    Some of the new V8 Man's would be a good choice. MAN also has HP levels to bridge the gap between the C18's and C32's as far as HP goes. They are indeed quieter than the cats. The C18's, while they are noisy, they are definitely not as noisy as a set of 12v92 TA's. The C18's are bulletproof motors and MUCH more fuel efficient than the C32's, by a LONG shot. Quite honestly, you rebuilt the DDEC's, finding parts for them is still possible, run them until you have a failure, OR until you have a buyer willing to pay good money for them, it's not like you're going to get a ton of money selling the 12v92's.
  15. PacBlue

    PacBlue Senior Member

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    Heras a snapshot of the 12V-92TA:

    upload_2019-7-25_9-17-10.png
    1040 is the shaft horsepower. There was an 110hp DDEC Version at the end of the production run.

    The big benefit you will get is a tremendous weight savings:
    12V-92TA = 5,861 lbs. dry
    CAT C18 = 4,101 lbs. dry
    MAN V8-1200 = 4,278 lbs. dry. They also have a de-rated 1000hp version that is 3,925 lbs. if you don't need to go above 1000hp.

    The weight savings is a great trade-off to add a SeaKeeper and still be less than the overall Detroit Diesel engine package weight.
  16. DOCKMASTER

    DOCKMASTER Member

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    I appreciate all the input. It would be difficult for me to seriously consider MAN's. Not because they are not good engines but the service and parts are just not available in my area. Whereas MTU would be a little better, still a challenge. Further, I have a business relationship with our CAT dealer so that helps quite a bit.

    Noise consideration is not my main objective although I would be dissapointed if it were louder.

    I may be able to shoe horn in C-32's but outboard access is already difficult with the Detriots and the C-32's would extend another 4-5 inches outboard. Then there is consideration of bigger shafts, struts, exhaust , etc ,etc. And with C-32's I don't know what it would do to the handling characteristics of the hull. Would I develop some chine walking or tail walking issues? The current configuration is rock solid which of course is great.
  17. DOCKMASTER

    DOCKMASTER Member

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    The spec sheet I have indicates the 12V-92TA dry weight is 4,895 lbs dry. Not sure where you found the 5,861 lbs you indicate? I attached the sheet I have but I cannot confirm it matches my engines exactly. So I'm assuming roughly 1, 600 lbs weight saving from engines (800# each) plus another 400 lbs for batteries, chargers, and other stuff that can go away.

    Attached Files:

  18. Capt J

    Capt J Senior Member

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    If you're happy with the performance with the current 12v92's, you'll be ecstatic with the C18's. 85 GPH (both) at 80% load, and my guess between the weight savings, extra HP and etc is that you'll pick up 3 knots at cruise and top speed.
  19. olderboater

    olderboater Senior Member

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    My input is simple. If it ain't broke, don't fix it.

    You could easily spend a lot of money to get a boat to perform just as it does today. That's pretty much best case. Worst case is you spend a lot of money and struggle to get it right and performing as it does today.
  20. PacBlue

    PacBlue Senior Member

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    I had a Detroit Diesel 12V-92TA spec sheet as well, maybe a little older, it may have also included the large factory gearbox in the 5,861 lbs.

    The CAT C32 weighs 6,780 lbs. and is too much iron in my opinion. The MTU 10V2000M86 at 5,082 lbs. gives you 1360 hp and would get you to 35 Knots if speed was on your mind.

    If you are keeping the boat for the next 5 - 10 years, I would go with the repower and enjoy the benefits.

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