Cummins vs Yanmar

Discussion in 'Diesel Engines' started by vjb, Jun 4, 2006.

  1. vjb
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    vjb New Member

    I'm trying to decide between the Cummin's QSB5.9 (350hp) and the Yanmar 6LYA (370 hp) to put in a 31' downeaster. They both seem to be great engines but parts availability, price and service for the Cummins are a little better in my area. Another big consideration for me is noise. My friend has a 31 Duffy with a 1990 Cummins 300hp and it is very noisy. I think the new QSB5.9 is a lot quieter. Any suggestions, opinions, ideas would be greatly appreciated.
     
  2. RANCHI OTTO
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    RANCHI OTTO Naval Architect

    Look at consumption curve...
    Good engines both, but I prefer Yanmar, more modern and less noisy...
     
  3. Vega
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    Vega Senior Member

    I would look at the three curves, power, torque and consumption and I would try to see what is the most favorable engine regarding performance and consumption at the power and rpm that you will use it most of the time, I mean, at your cruising speed.
     
  4. marshmat
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    marshmat Senior Member

    Noise will be determined more by how you hook up and muffle the exhaust, than by the make of the engine. If quiet is an issue, mount big mufflers and wrap them in the appropriate sound-absorbing insulation. I agree with Vega's advice on comparing the rating curves, this is the best way to see what a given engine will do with your hull.
     
  5. FAST FRED
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    FAST FRED Senior Member

    I would give both engine sellers a call and ask for the price of a rebuild, and the price of various parts you might need.

    How much for a rebuild kit?
    How much for injectors or the fuel pump?

    And of course the hard question , how long would it take to get the repair stuff.

    For a work boat the Cummins (or a Cat) would be first choice , for a 200hour a year fun toy the Yanmar might be lighter & cruise faster.

    FAST FRED
     
  6. Vega
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    Vega Senior Member

    I guess you are talking about the big engines of Cummins Marine (above 15 liters), because the smaller engines (mercruiser) are very similar to the yanmar. As Ranchi Otto has said, the Yanmar is a more modern engine.
    But I agree with you about comparing maintenance schedules and prices of pieces.

    Cummins Marine, a division of Cummins Inc, focuses on marine propulsion engines above 15 liters of displacement and auxiliary engines and gensets from 37 kW. Typically, these products are applied in commercial applications on a vessel that earns revenue.

    Cummins MerCruiser Diesel, a joint venture between Cummins Marine and Mercury MerCruiser, focuses on marine engine applications below 15 liters for yachts, sport fishing boats, trawlers, military craft, commercial vessels and more”
    http://www.gce.cummins.com/mce/mce_pages/productpage.htm?SMSESSION=NO
     
  7. StianM
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    StianM Senior Member

    Yanmar
     
  8. dougfrolich
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    dougfrolich Senior Member

    I have been ivestigating a similar situation, I have looked at the Yanmars,Volvos,Cats, and Cummins and the Yanmar Is lighter for power from 370 to 500bhp, and has a lower profile than the others. So for my application a couple of extra inches in ht. and lower weight made the choice easier.
     
  9. dougfrolich
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    dougfrolich Senior Member

    See Attatchements
     

    Attached Files:

  10. FAST FRED
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    FAST FRED Senior Member

    http://www.steyr-motors.com/products/products.htm


    These guys claim lots of power for very little weight , but their service life here in US is still unknown.

    Any one ever been shipmates with one?

    250hp at 322kg sounds light, with a Commercial rating!

    FAST FRED
     
  11. Frosty

    Frosty Previous Member

    I considered the Steyr before I bought the yanmar 6 LP. They were cheaper and yes lighter. However I was put off by the fact that the engines I was looking at in the 250HP range had no cylinder head. It was a full casting in so much as the head was part of the block. Ok no head gaskets to worry about but a valve job would be a major overhaul. It also had some wierd alluminium housing that wrapped the engine,--- Na I went for the yanmar 6LP. I cant say that I would do so again, but for my use they have been ok. 3 years now and still only 160 hours, so with work like that Yanmars are ok.
    They are a very high maintenance engine though, lots of zincs every 6 months and Yanmar talk of changing mixing elbows at 12 month intervals. I fresh flush so I have escaped that. There is also a cam belts to worry about needing changing at 1000 hours.
    The Yanmar 6LP is a Toyota 1HD engine from the Landcruiser. So all you guys who think marine engines are special ??????
     
  12. StianM
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    StianM Senior Member

    They are used in some MOB boats in the north sea and I belive the austrian miletary use them too.
    They are that light because they are in aluminium alloy.

    I't quite easy to remove.
    How often is a valve job required? In My father's boat we had to remove the top's 3 times on the kad's and two times it was broken gasket and 1 time it was broken cylinder liner and piston and we just changet the whole engine since they where 5 years old annyway and it is a ambulance boat in frequent use.

    If we where going to change engines again it would be the steyr with no doubt.
    Monoblock is great since you actually newer nead to remove the top and if you are doing a valve job it's pobartly time for a full overhault annyway so you nead to take out the whole engine.
     
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  13. Vega
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    Vega Senior Member

    StianM, very interesting.
     
  14. Frosty

    Frosty Previous Member

    Yes OK a valve job is not a very common occurence. However the Steyr is a belt driven cam, again Ok so is Yanmar,these can fail, not only for the belt falure but for tensioner failure.I am not sure if the Steyr is a safe engine in so much as it can tolerate a cam drive failure. I know the Yanmar cant, but if the yanmar split apart I can get a new head. I can also get spare parts and as I said in my last post it is a Toyota motor. I have never seen a Steyr dealer here where I do my boating.
    I hate belt driven cams, just a 10 dollar bearing failure on the belt tensioner jocky wheel is a major disaster. I suspect the styer could be a throw away motor
    I am not really a Yanmar enthusiast but it seemed to me at the time and still is the better choice.
    The price is very attractive to boat builders and where I saw them at the Sydney boat show In 2003 they were really pushing them, they were offering them in all packages and gearbox configerations including a surface drive package.
    If I was looking for a motor for a yacht, then I would reconsider my chioce. I also feel that the exta few thousand dollars for a Yanmar puts more onto its second hand sale value.
     

  15. Ari
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    Ari Patience s/o Genius

    Jack frost, you mean that if I have a Toyota Land Cruiser engine, should be no problem to fit it to become marine engine ?I do really like Yanmar engine but I never know actually they are Toyota..!
     
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