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Repower Hatteras 58 CPMY?

Discussion in 'Engines' started by ranger58sb, Apr 22, 2021.

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  1. Pascal

    Pascal Senior Member

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    They ll last what at 550hp? 1000 hours ?
    Jdow and boatpoor like this.
  2. Pascal

    Pascal Senior Member

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    The overall repower costs between the two is minimal. Not worth repowering with the smaller engines.
  3. Capt Ralph

    Capt Ralph Senior Member

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    Displacement is my best friend. When you can afford it, go for it.
    HP comes along much cheaper for the long ride.
    I'm still shopping (window dreaming) for a QSM set.
    Last edited: Apr 23, 2021
  4. Capt Ralph

    Capt Ralph Senior Member

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    He won't even tell us what he is smoking. Must be Oregano based thinking 92s are superior over 71s.
  5. Capt J

    Capt J Senior Member

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    I ran a 58' Yachtfish for a lot of years. It had recently rebuilt 8v92 TI's that were 550HP but detuned during the rebuild with 90CC injectors instead of the 110's it came with and dropped HP to around 465. It cruised 13.5-15 knots depending on fuel/water load. However, did 21 knots WOT. The motors did run crystal clean, even after doing slow speed for hours on end.

    The Yachtfish MAKES the 53' into a MUCH better boat IMO. You have a way to board in a stern in slip that's easy to get on and off, double the water capacity, 350 gallons more fuel, more storage, can fish, dive, or get on and off of a tender MUCH easier. Getting the stern lines from the 53' Aft deck REALLY sucks when backing into a slip......

    I would repower with more HP and agree with Pascal with this, you can always run hull speed and get the same economy. BUT, at 21 knots WOT the boat was an ENTIRELY different animal. It didn't roll like crazy like it did at cruise speed in a beam sea, it was incredibly more stable and tracked straight. If you could get engines to cruise it like that, I'd go for it. But again, I'd probably go newer. Because it doesn't end with the motors, might as well put a new gen, swap over to 24 volts, and on and on and on.
  6. mapism

    mapism Senior Member

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    It wasn't the saving on installation the reason for my suggestion.
    Just for sake of doing a bit of math, what's your typical cruising speed?
    And at that speed, what sort of fuel burn do you get?
  7. mapism

    mapism Senior Member

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    If 930hp only managed to push the hull at 21kts, in order to make the boat capable to cruise at that speed you should install at least 600hp each side, possibly more.
    I'm not arguing that the boat was more stable at that speed, but have you ever come across anyone with a Hatt MY of the vintage which is being discussed who is actually cruising at much more than HALF of that speed?

    My humble suggestion to anyone willing to cruise at 20+ kts would be not only to go newer, but also for a completely different boat altogether.
  8. Pascal

    Pascal Senior Member

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    Yes the 58 YF is a great boats with advantages River the 53. No doubt.

    Most of the time we cruise at hull speed (9.1/9.2kts) sipping about 9 to 10 GPH. The boat feels great at fast cruise of 17kts. Very solid and stable.

    That said we haven’t used the boat very much since the repower 2 years ago. No time. And whatever feee time we have, we also have a little daysailor I built begging to be taken out for a sail

    when going to the Exumas with the 84 I run, without guests on board, we usually run at hull speed too (just under 11kts). It s more relaxed and less wear and tear.

    where the old Hatteras hull shines compared to most modern boats is in its ability to cut thru head seas. No slamming no banging. Just cut thru.

    the best old Hatteras hills are the 80s 53+ when they wend to a wider beam. More space inside, better visually and better stability. The 56 MY is very nice

    I really don’t find the lack of cockpit to be a problem when line handling unless the owner has enclosed the aft deck or cluttered it with furniture. We set all the lines from the deck. My rule is Nobody gets off until the boat is secured. We either throw the lines around pilings and bring the bitter end back, and so the same with cleats.

    what I really do not like are the extended deckhouse with no walk around. That makes line handle more difficult
  9. Capt J

    Capt J Senior Member

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    Yes I have. At least 50% of owners of them still run them as yachts and run them at cruise speed 80% power. If you're going to run at hull speed (8.5 knots on the 58' YF), the difference in fuel burn between running 450hp diesels and 600 hp diesels at slow rpm to achieve hull speed, the difference in fuel burn is so minimal it shouldn't even be discussed.

    That being said, if you're just going to run the yacht at hull speed the Detroit Diesels 2 stroke with their blowers are incredibly more fuel efficient at 1000 rpms and lower than a modern 4 stroke. A 12v71 TI at 1000 rpms burns 5-6 GPH, a 800 HP MAN (or cat etc)burns 8 gph.
  10. echo charlie

    echo charlie Member

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    I spoke with FANFARE at the SAMS site , when he re powered he called Jack Hargrave ,and Hargrave suggested 6V92 550hp motors . FANFARE says he cruises a 17-19 knots. I do not know about the longevity. He re powered from 8V71N to 6V92TA's with the single turbo.
  11. mapism

    mapism Senior Member

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    Agreed, fuel burn is all about horsepower demanded by the props, and the size of the block providing whatever power is takes, doesn't make a huge difference.

    But let's take the 50% of owners who is happy with hull speed only, and let's assume that one of these chaps is considering a repower.
    According to Pascal numbers, his props only demand about 170 to 180 hp overall, to keep going at 9 kts (my estimate, based on his fuel burn numbers, but I don't think to be far off the mark).
    He also says, even if that's his cruising speed "most of the time", that the boat runs well at 17 kts fast cruising, and obviously anyone interested in keeping that option has no other choice than repowering with "big" engines.

    OTOH, anyone else willing to accept the restriction to hull speed only could pick the engines having in mind the previous numbers.
    In other words, it wouldn't be a matter of chosing 450 or 600 hp engines, because 150 hp each side would be sufficient.
    OK, make it 180 or 200 if you want to exaggerate, for sake of having some reserve for rough sea conditions.
    But now you're talking of a completely different league anyhow, in many ways: MUCH smaller and lighter engines and gearboxes, less expensive maintenance, better e/r accessibility, engines optimized for running efficiently at hull speed forever without potential drawbacks (hence also with somewhat lower fuel burn) - you name it.
    You could even go for smaller shafts, if for any reason the existing ones should be replaced.

    BTW, I still think that anyone willing to cruise at 20+ kts would be better off with a completely different boat than a Hatt 58 MY, but each to their own on that, of course.
    Last edited: Apr 24, 2021
  12. Capt Ralph

    Capt Ralph Senior Member

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    What ancient history are you talking here?
    Recent history would not replace one dinosaur with a worst dinosaur.
    We can banter this all day. Al else can recognize an oregano support therapy for you.
  13. Capt J

    Capt J Senior Member

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    200HP modern diesels wouldn't have the torque to make the boat handle correctly in certain conditions, docking/maneuvering in a lot of current/wind, etc. etc. Could they work, yeah.......but then you're getting in additional cost of new props, and other things when repowering with small engines......I don't think anyone thinks it's economically feasible to repower one of these yachts with new diesels, BUT a few people don't care about that. This was my first real yacht and I'm keeping it forever attitude and don't care what it costs.

    Repowering old detroit 2 cycles to 6v92 2 cycles is ridiculous in todays day and age.
  14. DOCKMASTER

    DOCKMASTER Senior Member

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    If you want to Repower with 2 strokes I’ve got a great, complete set of 12v92’s I’ll sell you cheap. :):)
  15. Capt J

    Capt J Senior Member

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    Will you sell 1, so the guy can take it apart and make 2-6v92's out of it? hehehehe.
  16. Pascal

    Pascal Senior Member

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    No it may not be economically feasible but what are the alternatives. I already have put close to $250k in my 53 and by the time I m done it s going to be $300k. Not counting the cost of the boat itself but when I started, with bad engines and a tired ... well everything... it was worth nothing.

    what could I get for $300k with:
    - huge aft deck (bigger than the new Hatt 56)
    - big foredeck with huge sunpad
    - a master stateroom bigger than many 60/70 footers... heck I even have a hot tub in the head...
    - nice side decks
    - lower helm with side doors for single handling
    - big flybridge
    - a roomy VIP forward, bigger than any modern 50 footer
    - a real galley, up

    and reliable Cummins, modern Trac stabs, all new electrical and plumbing.

    Honestly I don’t know what I could get with all the above for less than twice what I will have spent.
    MACKLIN, T.T., MBevins and 1 other person like this.
  17. echo charlie

    echo charlie Member

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    Pascal , I agree 100%.
  18. mapism

    mapism Senior Member

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    Naah, if a pair of 200hp engines couldn't handle a Hatt 58 MY, how could a single 325hp deal with a Nordhavn 60 weighing twice as much?
    I see no need to replace the props either, it's just a matter of finding an appropriate gear ratio.

    That said, I'm not trying to convince anyone to repower a 40+ years old boat, mind.
    The OP said he was considering something built in the late 70s, and just in case he's thinking that GRP can last forever when well built, below is a pic of a hull of the very same builder and vintage.

    But as a liveaboard boat and for some slow pace cruising, a downsized repower could make sense.
    And as Pascal pointed out, for the same ballpark money you certainly wouldn't be overwhelmed by the offer of much better modern boats...
    [​IMG]
  19. Pascal

    Pascal Senior Member

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    Blisters aren’t much of a worry on these boats. I d rather have blistered Hatteras hull than a poorly cored newer boats. Blisters have never sunk a Hatteras... many others have nearly sank or required massive repairs because of coring issues. Sea Ray, Azimut, tiara, and many many more.

    after hurricane Irma, my boat had a section of toe rail that was ground open over about 15 to 17’. The aft port ER bulkhead had been pushed inside by 2”.
    Nothing was holding the hull side. Not only did the boat survive but there wasn’t a single stress crack on the hull side. It was the only boat to survive at the end of any piers at my marina. None of the other newer boats made it.
  20. mapism

    mapism Senior Member

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    I agree that some cored hulls can give even worse headaches, but dismissing the above as blisters is a massive understatement.
    I appreciate it's hard to tell from the photo, but trust me: in some of the osmosis patches above, the thickness removed by scraping the softened parts went way past the gelcoat, and in some places the GRP left was barely enough to withstand a finger pressure.

    But yeah, the boat didn't sink, and neither I was suggesting that she did, in fact.
    All I meant is that engines are just one of many things to consider when dealing with a 40+ yo boat, no matter how good the builder reputation is.
    After all, you also wrote that when you started, on top of repowering you had to deal with "a tired ... well everything", didn't you?