Big and slow or small and fast?

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

  1. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    The engine will spend 90%+ of its time just off idle around 1000rpm.

    A 4 cylinder air cooled Wisconson sounds ideal.

    Diesels stink at low load operation , slobbering , poor compression and high oil consumption come from using an engine at idle for most of its life.

    Less problem for gasoline engines.
     
  2. Red Dwarf
    Joined: Jun 2012
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    Red Dwarf Senior Member

    Thanks for all the help. I think Perkins is the way to go. I signed up at boatdiesel.com and will do more research.

    One idea I kicked around is to have 2 different size engines, one small engine for cruise and a larger engine for high speed. That way the cruise engine can run at a more efficient load.
     
  3. WestVanHan
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    WestVanHan Not a Senior Member

    It'd be cheaper to install the Perkins,and get a controllable pitch prop and load it up by varying the pitch.
     
  4. Red Dwarf
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    Red Dwarf Senior Member

    Yes, I am looking at the CPP options. Do you know how the Autoprop compares to a true CPP?
     
  5. WestVanHan
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    WestVanHan Not a Senior Member

    Have no idea about the autoprop.

    I do know that a CPP usually comes in fairly close to the price of a regular drive system.
    If I ever get any prop/trans problems on my boat,CPP is going in. As it stands,it's not worth spending the money when it's at 100 hours a year.

    There was a yacht builder on here a couple years ago,he put CPP in every yacht he built-many of them 20-30 meter expedition type trawlers.


    http://www.kastenmarine.com/CPprops.htm
     
  6. ErikdeJong
    Joined: May 2012
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    Location: Halifax

    ErikdeJong Junior Member

    I do not really have a personal preference for a brand, but if you are outfitting an expedition boat, I would personally look for a heavy slow running engine with preferable 6 cilinders in line.
    Parts, longevity etc. are all important, but comfort during the engine hours is a lot more! The big heavy slow many cylinder engines tend to make much less noise and vibrations than the jumpy lightweight high speed engines.

    I have an expedition boat myself and I'm using a 700kg heavy Ford 6 cylinder of 95hp only. While sailing 8,5 knots we can have a normal conversation, it is easy to sleep and even after having the engine on for 40 or 50 hours, your ears won't resonate after the engine is turned of.

    I think comfort is of greater importance than ease of maintenance or the price of parts. I am convinced that all engines that are sold in large quantities are of good quality given that they are built in properly. Most engine troubles are caused by the direct environment or technical installation, and not by the engine itself.

    If your choice is between those two engines, my personal pref. would be the perkins.
     
  7. Red Dwarf
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    Red Dwarf Senior Member

    After much searching and reading I have decided on the John Deere 4045T. Seems to be a solid engine, popular with the trawler crowd. And the price is awesome. I looked into a CPP setup but decided against it since I want to be able to shut one engine down for ultra economy cruise. I am looking into either an Autoprop or Gori prop.

    It will definitely be keel cooled and possibly dry stack. I like the idea of no salt water at all but I like the quieter water jacketed exhaust manifold and the additional muffling of exhaust sound from the water injection into the exhaust. I may run a normal dry cast iron exhaust manifold but still use water injection into the exhaust for the cooling and sound reduction.
     
  8. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    I am looking into either an Autoprop or Gori prop.

    Beware , usually these do not provide the push of a stock cheap 3 blade of similar size..

    Dry stack can be as quiet as your car , just a matter of muffler installation. Search "Hospital Critical Exhaust" if you want whisper quiet.

    And dumping the exhaust ABOVE the boat has many advantages in terms of stench blowing IN the boat.

    The Deere can be had at very fine prices if not bought from the "marine" dealer.

    The JD tractor guys sell factory rebuilt engines with NO CORE CHARGE , at 2 or 3 "sales" a year.

    Couple that with a rebuilt Twin Disc of the correct size and ratio , and your away at less than 1/2 "Marine price".

    Might save enough to get that CPP ???
     
  9. Northeaster
    Joined: Sep 2011
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    Northeaster Senior Member

    Can I ask roughly what one would pay for the John Deere, and what kind of gearbox (and ratio) that would come with?
    Would love to hear prices for rebuilt (tractor) equivalents as well.
    Thanks!
     
  10. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Can I ask roughly what one would pay for the John Deere, and what kind of gearbox (and ratio) that would come with?"

    That is between your local JD tractor dealer and weather there is a "sale" on.

    Sale = no core charge.

    The tractor engine will come with NO transmission,

    You purchase a marine tranny from a marine re-builder .

    You select which tranny series and the gear ratios to match your installation.

    Look in "Boats and Harbors" magazine for tranny sources.

    Twin Disc would be first choice for longevity.
     
  11. Red Dwarf
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    Red Dwarf Senior Member

    Go here and check out prices.

    http://www.dieselenginetrader.com/engines.cfm?ID=40

    There are rebuilds around $5k and new at $8750. Add a trans and you are easily still under $10k. I am not using a marine version but if you need one you can pick up the marine parts and do the conversion yourself, it will add a couple thousand to the price.

    That saves over 20K vs the Yanmar. Since I need two engines the savings pays for another year of cruising.:D
     
  12. liki
    Joined: Nov 2008
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    liki Senior Member

    There are also CPP setups that will rotate to 90 degrees pitch for sailing.
     
  13. Red Dwarf
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    Red Dwarf Senior Member

    I looked into that and was told that in order to get the travel needed to feather the prop for sailing you lost reverse so a normal fwd, neutral rev gearbox is needed. If I have to get a normal gearbox I figure I would just get a normal feathering prop and save the CPP money.

    I think the CPP is a problem with smaller boats since our motors can not drive the prop 1:1 so you end up having to buy some sort of reduction box anyway.
     
  14. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    A reduction gear box is very desirable to allow a smaller engine to turn a larger prop,required for efficiency.

    One hassle with a CPP alone is at anchor the engine must be set to a specific no thrust position at a certain RPM before shut down.

    On cold start the engine will not run at warm idle speeds , so if this precaution was not taken , the boat would want to move.

    On cold start the throttle is advanced to the prior shut down RPM , and the boat is stationary.

    The gear box takes care of all this , while producing far easier boat handling , shift from FWD to REV docking , rather than crank a handle.

    THe CPP is a delight in light airs as the boat can be sailed , the engine at just above idle (Quiet but makes good refrigeration or electric) and normal transit speed obtained.

    The ability to do this wonderful performance comes from the pitch control you have , a sailing prop of any brand wont do this, regardless of what their advert dept claims.
     

  15. WestVanHan
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    WestVanHan Not a Senior Member

    FF...news flash...they have neutral,and have had for decades.

    CPP can go on behind a standard transmission anyways...but whats the difference between moving a CPP lever and moving a transmission lever?
    I'll tell you-instant change of direction,so it's actually easier to dock a CPP.


    Hydraulic controlled CPP have been around for 60 odd years and proven themselves.
     
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