Big and slow or small and fast?

Discussion in 'Diesel Engines' started by Red Dwarf, Sep 12, 2012.

  1. Red Dwarf
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    Red Dwarf Senior Member

    I am looking at 2 different 150Hp engines. One is a 4BY2-150 from Yanmar and the other is a M150Ti from Perkins.

    They both have similar complexity and systems. The Perkins is 6 liters vs the Yanmar's 2 liters. The Perkins redline is 2600rpm while the Yanmar is 4000rpm. The Perkins weighs over twice as much as the Yanmar. They seem to have virtually identical fuel consumption.

    So which is a better choice for an expedition style yacht? Imagine long periods of low load operation. Reliability is paramount and worldwide parts is important.
     

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  2. WestVanHan
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    WestVanHan Not a Senior Member

    Perkins-no doubt
     
  3. Petros
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    Petros Senior Member

    you can not tell based on this kind of analysis. Consider car engines, Honda has made very complex, high RPM, all aluminum, very precision engines for their cars for many decades, yet they will reliably run with minimal maintenance for 200,000 plus miles. Yet the old chevy and ford truck engines are much larger, cast iron, much slower and actually have fewer moving parts, but their useful life is less than half that of the honda engine, and often they require major repairs long before the honda. And many times major repairs are needed when these engines are still under warranty (far far less often than the Honda engines).

    You have to go by the historical reliability of that company's product, and preferably that particular model of engine. Not all Japanese products are superior to US or European ones, it just depends on the maker and their track record. Using the kind of simplistic criteria you listed above could lead you to making a big mistake.

    Find out the reliability of the engine you are considering, if they are the same, than find out the cost of replacement parts and how wide spread their availability is in the places you intend to visit. I have heard of someone stuck in the south pacific islands waiting weeks to have a $200 part delivered from the US, that cost $700 to have shipped, and than have to fly a mechanic in from Tahiti to get their yacht repaired.

    Would have been better if the part did not fail. But when it failed they had a back-up plan (like a spare) and if they had something common enough to get locally that locals can likely fix (or even better, know enough about all your systems to be able to fix it yourself if you have to).
     
  4. whitepointer23

    whitepointer23 Previous Member

    john deere.
     
  5. FAST FRED
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    FAST FRED Senior Member

    For your use it is better to look and see if the engine is RATED for the service you wish to do.

    For a speed boat its one rating , for 24/7 its a vastly different rating .

    If the engine is NOT rated for your use , I would look further.

    Auto marinizations will seldom be for any use that requires long endurance , unless severly de rated.

    "run with minimal maintenance for 200,000 plus miles. Yet the old chevy and ford truck engines are much larger, cast iron, much slower "

    Not a realistic comparison as the "new" engines have parts computer measured and matched for a precision fit.

    The antique Fords and Chevys were stuck together with parts to a certain specification only, BIG DIFFERENCE.
     
  6. WestVanHan
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    WestVanHan Not a Senior Member

    Fred said what I was going to but didn't bother- 150hp on the Yanmar and 75 hp per litre is intermittent maximum rating-maybe 30 minutes or half hour a day- I'd guess around 100 hp continuous-50 hp per litre.

    The Perkins,at 25 hp per litre that rating is continuous...and from my experience up to 3000-4000 hours a year.


    So,despite Honda engines being good and old truck engines supposedly not and having nix to do with this...once again-Perkins.
    Or Cummins.
     
  7. Red Dwarf
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    Red Dwarf Senior Member

    I did some searching and can find nothing bad about either the Yanmar or the Perkins. They both seem to be reliable with a good support network for parts.

    WestVanHan - Can you elaborate on why "Perkins-no doubt"?

    The equivalent John Deere is the 4045TFM50. Funny that it is 4.5 liters right between the Yanmar and Perkins.

    I agree the engine construction and engineering is what really matters. I have a Cummins 6.7l in my Dodge truck and it is as solid as a rock. On the other hand I used to have a Honda S2000 and loved to redline that baby every chance I had and it was also as solid as a rock.

    That is one reason I ask about the comparison of the two engine philosophies of small high revving or large slow revving. I am hoping those with experience in a marine application could enlighten me.

    The application I have in mind places such a low demand on the engine that normal lifecycle estimates vs load don't really apply. The engine will spend 90%+ of its time just off idle around 1000rpm. In fact I could use an engine with half the horsepower but I want the option of a higher speed in the event I need or want it.

    The extremely low demand on the engine introduces its own problems with not high enough egt's too burn the gunk out and keep the rings and cylinder walls happy. I think that can be mitigated with a burst of high throttle and proper egt's for a few minutes every few hours.

    Sunreef built a expedition version of their 70 ft cat and remapped the engine to reduce fuel consumption and allow sustained low rpm, 1500rpm, operation. In fact the fuel burn is 7.5l/hr/engine at 1500rpm which provides 10 knots. Not bad for a 40 ton boat.

    The reason I am researching this is due to the huge difference in weight of the Perkins and Yanmar engines. I can literally carry a spare Yanmar for the weight of one Perkins. How's that for a backup plan? But seriously the weight difference is great enough that it does affect the layout and balance early in the design.
     
  8. Petros
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    Petros Senior Member

    will all things being equal, the engine with the lower stress should last longer. However they are not equal, so you have to look at reliablity. If they are identical reliablity, and parts availablity, than I would go with the lighter engine since it is a more efficient design and should also deliver better economy.

    I do not know anything about either engine, but I do know a lot about engines in general. I have worked as an automotive engineer, designed several engines that went in fully sponsored race cars, been a mechanic to pay for collage and still work on old cars. You have to go by reliability history for each engine.
     
  9. mydauphin
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    mydauphin Senior Member

    If weight is the issue then not the Perkins. If durability and ease of maintenance Perkins. The Yanmar will be long gone before the Perkins is even broken in.
     
  10. WestVanHan
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    WestVanHan Not a Senior Member

    I had an s2000..zinging it off 9000 for a couple seconds here and there means nothing when it is .0001% of it's running time.And they had more than their share of problems anyways-even with gentle driving...the warranty claims and lawsuits for burning oil really hurt Honda.
    I'm 6'4 + hardly fit in the thing,only drove it with the top down.

    The Deere 4045 is a great engine,however I think it's continuous is around 90-100 hp.

    Why Perkins? That engine has been around almost 20 years since about 1995 IIRC, has a Bosch rotary pump with simpler injection,and is proven.

    The Yanmar-be great for a coastal boat,not sure what the engine is based on and it has the full ECU/ piezo/ high pressure common rail injection.Think they've only been out a couple years ??? If one tiny resistor on one chip in one module burns out-what do you do?

    Which would you rather work on?

    But what you need to do is actually figure out how much hp you need and pay $25 for a boatdiesel.com membership.
     
  11. mydauphin
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    mydauphin Senior Member

    The basic Perkin with Bosch Pump has been around for longer than that. I have worked on some units from the 1970's and they are still working with minor tweaking. Had a guy pour water water in our diesel. After the motor died from water in the injector, we opened up the lines, and the plug on pump, crank it and it started fine in few minutes. Try that on a new common rail system.
    The Perkin and Deeres are very similar, some engines I believe were built by one for the other at some point. I don't remember well. My trans-decade memory is failing me.
     
  12. mydauphin
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    mydauphin Senior Member

    One issue I have heard with the Yanmars is corrosion due to their alloy parts. Perhaps someone can talk about that.
     
  13. WestVanHan
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    WestVanHan Not a Senior Member

    Perkins put engines into tractors and was owned by a tractor company for a while.
    Think you're right but IIRC the 6-354 got a new modern head in the mid 90's and a minor block tweak to change it to the 6 litre.

    At any rate,you'd likely see 20,000 hours out of it
     
  14. Petros
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    Petros Senior Member

    I have owned a number of mechanical pump diesels in older cars and trucks, even a in an old farm tractor. they have their issues but once you know how to bleed the lines, keep the fuel supply clean, etc. they run forever. The farm tractor engine was over 50 years old and still running great (it was a 4 cylinder continental in an International Harvester). The modern electronic fuel controls are forced on the manufacturers for emissions reasons, and have not proven reliable over very long term. So unless you carry two or three back up ECU and related parts, I would go with mechanical injector pump any day, even at the cost of slightly higher fuel consumption.

    Those two engines are not equivalent, one is modern the other much older, and proven, technology. As I stated above, I do not know a lot about marine engines, but I have lots of experience with land based cars and trucks. You should still carry spare parts, but I would do it selectivly, find out what can fail and likely leave you stranded. Know how to fix it, and have a tool kit along, and you will be unstoppable. And likely save yourself a lot of money over being stuck somewhere needed parts to be shipped from Toyko, hand carried to your location.
     

  15. tunnels

    tunnels Previous Member

    Perkins !!:D
     
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