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Should I buy a boat with IPS drives?

Discussion in 'General Yachting Discussion' started by Max Waibler, Apr 29, 2020.

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  1. mapism

    mapism Senior Member

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    I don't think it should be necessary to ask anything special to the dealer, actually.
    If they repowered the P680 with the 1350 instead of the 1200, by definition the builder must have propped the IPS according to the higher power.
    Among other technical reasons, that's also necessary for passing the seatrial check upon commissioning, required by all engine manufacturers to validate their warranty.
    The basic rule is always the very simple and old one, also for IPS: the boat, when loaded, must achieve the rated rpm and 100% load.
    Speed is just a dependent variable, so to speak.

    Btw, the 1350 package is essentially powered by the same engine as the 1200.
    In fact, as you surely know, the IPS naming is just a meaningless marketing trick.
    What actually powers the 1200 package is a 12.8 liters engine with an output of 900hp @ 2300rpm.
    And the 1350 is powered by the very same block, spiced up to produce 1000hp @ 2400rpm instead.
    So, with his new P680, what your son in law will actually get is 200 more hp in total, at a higher rpm, and with 700+ additional lbs in the e/room.
    Now, I know absolutely nothing about the P680 performances, but having an idea about how much this sort of difference can affect a 70 footer weighing almost 100k lbs when loaded, well, on one hand I wouldn't call it trivial, but I wouldn't hold my breath for a much higher speed either.

    In fact, I wouldn't be surprised it the builder should even install on the 1350 some slightly shorter props compared to the 1200, to allow for the additional 100 rpm the engines are rated for.
    The 1350 boat could (and should!) still be a bit faster of course, depending on how the prop pitch and the higher rpm combination works out - but not much, I would guess.

    Anyway, my whole point is that also with pods, like with shafts or any other transmission, there is no magic propeller that can be used to make the boat go faster, because also pods are constrained by physics as anything else.
    What makes a big difference is the well known rule that drag becomes more critical as speed increases, and in an exponential rather than linear manner.
    THIS is the reason why pods don't make sense for powering fast boats: at high speed, you don't want two propellers on each side, neither large blades, nor a large diameter hub, not to mention a large chunk of metal - neither in front nor behind props.
    As much as you don't want a long shaft spinning and a P bracket, of course.
    In this respect, leaving aside waterjets which are more tricky, the comparison with surface transmissions is mind boggling, just by looking at them.

    Of course, you can still make also a pod powered boat go fast (up to a point), by just throwing more power at it, but the faster the boat, the higher the drag losses and the lower the overall efficiency.
    Btw, that's the same reason why duoprop outdrives on speedboats are totally unheard of.
    It's as simple as that.
  2. AMG

    AMG YF Moderator

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    Both yes and no. If they should name the IPS/1350 as an IPS/1000, all the competition would look a lot weaker with less performance...
  3. HTMO9

    HTMO9 Senior Member

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    Talked to my son in law this evening. He knew already about the different props available. The Prestige 680 with twin IPS 1350 is equipped as standard with the "normal" props for a good balance of top speed, economy and acceleration. The "high performance" props are giving a bit more top speed with lower acceleration and higher fuel consumption. He will take the standard props, as he is not interested in the last Knot of top speed. They cruise a lot on rivers and other speed restricted areas but he likes the better acceleration. He has driven both the IPS 1200 and 1350 already. He says, there is a difference in performance. But the main reason for the new boat ist the different lower deck layout. His present boat has tripple double cabins and the new one will have two double and two twin cabins. Both with one additional crew cabin. A better setup for two families with two kids each during a weekend cruise.

    4c4630878456a4d610009b69dfab3911.jpeg 6ec2e46826dae8697b043cbb6a80f77b.jpeg

    But if son Nr.1 goes for a larger boat with permanent crew (his license is only valid up to 24 meters LoA) and still wants to see 40 Kts, I will strongly advice him to go for the Q-SPD drives and MTU engines. My choice would be a Pershing 108 with tripple MTU 16V 2000 M96 L engines, if they could be talked into those surface drives. I would definately not go for Arneson drives and not again for a fully custom one-off. To much trouble, far to expensive and it takes far to long to build it. Too bad Delta Power Boats is not ready for and with the 105.
  4. Capt J

    Capt J Senior Member

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    I don't think the Prestige's are exactly a fast hull or fast boat, so you're better off with the standard props.
  5. mapism

    mapism Senior Member

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    LOL, well, that's a way to look at that.
    By the same token, it also helps making the fuel burn of 900/1000hp engines appear lower when considered as 1200/1350hp, I suppose... :)
  6. mapism

    mapism Senior Member

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    I don't think they will, and even if they would, I'd expect them to ask you to sign a release of liability agreement.

    See, both Twin Disc and ZF engineers could design fixed surface transmissions during their coffee break, if they wanted to.
    There are good reasons why the best transmission builders stick to steerable and trimmable transmissions, instead.
    What those nice Kiwis are now building is almost identical to what Intermarine experimented at length many years ago, together with Sonny Levi and his so-called LDU (Levi Drive Unit).
    But eventually, they didn't exactly flood the market with those boats and transmission, as I'm sure you know.
    According to an officer who used to be in command of a patrol boat powered by that system, the boat was quite simply "impossible to maneuver".
    But I suppose that less maintenance demanding, those Q-SPD things probably are - I should think so too!

    Anyway, best of luck if you would decide to give them a try and Pershing would accept your request.
    I for one would be curious to follow the progress of such project, if you would like to keep us updated on it!
    Last edited: May 25, 2020
  7. HTMO9

    HTMO9 Senior Member

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    During our shopping tour in the Med for my sons new boat, we have tested several fast boats in the 80 to 120 ft range. We tested amongst others the Mangusta 94 with KAMEWA waterjets and the Pershing 82 and 92 with Arneson drives. Both boats with MTU !6V M94 2000 engines (the M96 L was not available at that time). The Mangusta was ruled out, because even by using all homologation tricks available, the boat was to large for his licence. Both Pershing were within his license range and their performance were without any doubt really great. We also had the chance to participate on a demo tour with the tripple engine Pershing 108. This boat is a beast.

    The final desicision was made by my daughter in law, she got scared by the Arneson drives, their noise and their performance. But all three boats were not really built for the North Sea and the Baltic. That is the reason, he came up with this one-off custom build, Alloy Dutch quad IPS flybridge boat. The hull could not accomodate 4 IPS 1200 and so my son ended up with quad IPS 800. A great high quality boat with great comfort and smotth ride but only with 28 Kts top speed half load and 25 Kts cruise. In my opinion, the boat was far too expensive for its size and performance and the build took too long and caused a lot of trouble and travel. The boat has performed flawless up to now but my son was never really happy with it due to lack of speed.

    As his 2 kids are older now and my son relocated the boat finally to the Med, his wife agreed on a larger boat with permant crew and higher performance. So we are back on the market. What means, he makes the decisions, I may give some advice and for sure most of the money :). The Pershing 108 or the 115 are his favorite boats. And he would not have any problem with the tripple Arneson drives on the 108, that is just me who does not like them. If the best surface drive builder can easily built a great surface drive, why are those drives making so much trouble and produce so many failures?

    The 115 is a totally different animal with its MTU 4000 engines, its KAMEWAs and the center booster with jet turbine. But a really fantastic boat.

    The Beast

    ds_21454.JPG
    As soon as the borders to Italy and Spain reopen for us, we will start a new shopping tour in the Med. I will post the outcome. My other son in law and my second son and their families, thank God, are purebred sailors and if traveling on a boat, they visit me or use my boat(s).
  8. mapism

    mapism Senior Member

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    Because they are mechanically complex units.
    And mechanical complexity doesn't like being permanently submerged in sea water - pretty much as it doesn't with outdrives and IPS.

    But they are complex for good reasons.
    Fixed surface transmissions are right at the pinnacle of efficiency, if you want to use a boat always at her optimal design speed, optimally loaded, and you don't mind a maneuverability that makes every mooring a big challenge.
    It's no coincidence that this is the route Buzzi chose for his 80 footer that broke more records than I can remember (like the Venice-Montecarlo and Round Britain, just to name the most well known).
    On top of that, he fitted staggered MTU engines for best weight distribution and to spread the thrust between four of his own design Trimax combo (transmissions+rudders+trim tabs - see below).
    As a consequence, the engine room took all the space it deserved, because obviously he couldn't care less about internal amenities.
    Now, THAT is a no-nonsense setup designed for one and only purpose, i.e. go fast also in harsh sea conditions, and for very long distances.

    Pershings (as well as ABs, PJs, and the likes) are nowhere near so extreme, and while they are indeed designed to be fast, they are neither meant to need a race pilot to helm them, nor to make berthing a scary experience. Not to mention getting rid of gin-palace interiors in favor of tankage and other technical requirements.
    But if your son is willing to accept all the compromises that in extreme boats come with the territory, you could get in touch with Otam.
    In fact, they now build an 80 and an 85 based on that original Buzzi hull mould (both within the 24m license limit, btw).
    Much more civilized actually, with twin Cat C32 on Arnesons (still good for 40+ kts, mind!), because that's more than enough for most folks.
    But they might be willing to undertake relevant customizations - within reason, of course.
    More than Ferretti Group, I think.

    Anyway, your and your son's problem is a very nice one to have, that's for sure. :cool:

    [​IMG]
  9. Ranibd

    Ranibd New Member

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    What will be the cost now?

    Im looking to buy a Monte Carlo MC5 2016 with the IPS 600 , this thread is helping me a lot but also mix feelings about it.

    Any good tips will help
  10. Capt J

    Capt J Senior Member

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    There aren't really many failures with Arnesons if you exercise them regularly. It's only when they sit. If you work the drives up and down and side to side every 2 weeks, you won't have any issues. When you let barnacles grow on the rams, then seals start failing on everything.
  11. Saverio

    Saverio New Member

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    Hi Chris,
    Let me tell you about the bronze/SS seal. Actually it's not a seal but a collar that inserts between the lower and the intermediate unit. If yours are bronze, I suggest you change them with SS which are much more resistant.
    2 lips seals then go around the collar.
    To do the job you will have to haul out and off load the drives and bring them to a workshop. The job is very easy. The big problem is offloading and then remounting the drive back in the boat. They are **** heavy !!
    I did it and since then zero leaks.
    Hope this helps.
    Regards
    S.
  12. ranger58sb

    ranger58sb Senior member

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    Thanks. Turns out a moot point for us; we ended up buying a different boat...

    But that'll be useful for other readers as part of the collective knowledge here.

    Cheers, -Chris