Auto Diesel (Yeah, again, but...)

Discussion in 'Propulsion' started by Filmdaddy, Jul 21, 2005.

  1. gonzo
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    gonzo Senior Member

    Yes, you'll find an automotive Vortec at the junkyard.
     
  2. cyclops
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    cyclops Senior Member

    Film Daddy. The real life answer to the use of any engine in a boat will always be a, yes. Anything can and will power a boat safely. Not everyone was killed or injured before Marine engines were availabe. That said. You better be one experienced marine person. Can I do what you want to do. Yes. Will I risk other people around me if I forget a safety step? No way!
     
  3. Filmdaddy

    Filmdaddy Previous Member

    Gonzo - wow. You sound bitter. Bet you're tired of answering the same questions, expressing the same opinions over and over. Have a Bud on me, OK?
    Cyclops - thanks for the opinion. I guess I'm just a little tired of having vested interests tell me that I have to buy their product, or philosophy, or fuel additive or whatever. I just want to get a boat on the water economically, and with equipment that I can not only understand and afford, but find locally. Guess I stepped on some toes. Sorry.
     
  4. gonzo
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    gonzo Senior Member

    Tired I am, bitter no way. Why do you insist that a non-marine engine is a better deal? Do the numbers. Add up the labor and materials. Add the labor to that. Add the labor. Add the expense of experimenting- all the setups that don't work. When you have all that, then we can have a sensible discussion. I find it insulting that you claim my opinion comes from "vested interest". I've had to give the surviving relatives in boat fires or explosions an insurance check.
     
  5. Filmdaddy

    Filmdaddy Previous Member

    Gonzo - No offence was intended, believe me.
    The vested interests I referred to are the people at OMC and SABB and Awlgrip and everyone else that charges an enormous amount for anything with "marine" in the product description.
    I originally started asking about the auto engines because I understand them, and can afford to buy them and play with them and work on them.
    And because I didn't understand the insistence from you and others that boat motors always run at high power settings... 75-90%. So I asked questions. I simply don't believe that auto engines have to work WFO all the time. That doesn't make sense. But everyone says so.
    If anyone had ever said why auto engines have to run so fiercely, while 'marinized' engines apparently have some magic part or compound that lets them operate normally under the same conditions, then I would have had an answer.
    Experience is a painful way to learn important lessons. You are undoubtedly more experienced than I. You have done a lot more than I will ever consider. If I were your apprentice, I would be required to follow your lead rigorously. But I'm not.
    So, apparently by myself, I will continue to seek the answer to my questions.
    I apologize to you and anyone else who found my questions offensive. I won't be back. Perhaps somewhere else there is someone who can answer the basic question.
     
  6. fcfc
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    fcfc Senior Member

  7. gonzo
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    gonzo Senior Member

    Marine engine parts, including the block seem identical to the automotive. Differences are, for example, in the pistons. They are forged of hypereutetic alloys. Oil pumps are high volume. Blocks have nickel content in the alloy. Camshafts, advance curve and fuel delivery are set for the particular application. This changes from a skiboat to a cruiser.
     
  8. fcfc
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    fcfc Senior Member

    When you have 120 to 150 hp from a 91 cid (2 litres) automotive diesel engine lasting at least 100 000 miles, you already have all bells and whistle like forged or hypereutectic pistons, large oil pump etc etc ....

    The only difference I would think is camshaft timing and ECU programming or marinized ECU.

    Marine engine departments simply have not enough R&D money to do more expensive modifications on a already hi tech automotive engine which has costed billions to develop. They also have to deal with more typical marine things as exchanger, exhaust, mounting bed, electrical etc etc ...
     
  9. kmorin
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    kmorin Senior Member

    engine loading

    Filmdaddy, I believe the answer is that marined engines are more expensive for several reasons. They are hand built, (labor) they use small run high cost components (specialty parts of more expensive alloys and spec.s) and they are more brand sold to a market driven by name/cost ratios not often found in production autos. (move to italian or english hand made cars and the same market forces seem to apply)


    First the labor- detroit's engines (even japanese engines) are made by machine in huge numbers compared to marine engine numbers. The costs are spread over more units -overhead, parts, labor and profit are all done at a different scale. This makes a 2 or 3 to ratio in cost versus production run.

    Next the parts, some of which are mentioned here, are designed for higher loads. This may be mentioned but I will again, rolling stock have to overcome inertia to get going. They have transmissions to accomplish this, gearing works for rolling stock since the rolling momentum RESISTANCE drops as the auto speed up. In boats the resistance stays the same and GET LARGER. In a "tractor pull" contest- which you may have seen on TV the wt. is moved forward on the trailer as the tractor moves along the course; until it is literally on top of the pulling machine! In other words the work becomes harder the farther you go. Boats aren't quite that extreme but its a useful picture to compare -rolling stock drops resistance with gains in momentum, but water being what it is- boats' resistance increases or stays the same by comparison.

    This means the 1000 hour engine use in a car may have a 10% peak load of full torque- but in a boat it means the full time of full (or almost full) torque. To make engines serve in this application- everyone who sells them has learned, by engine failures, to modify the lower peak torque features from the automotive designed application engine for a higher peak torque use which is encountered in boats.

    Main bearings are beefed up, valve springs are doubled, pistons are changed, cams are reground, exhaust manifolds weighing a ton are hung on block lands intended for 1/5 the wt.......on and on it goes. Almost every modification is a higher per unit cost than the automotive application BECAUSE of the difference in numbers of units made, installed and sold.

    Since you seem more familiar with auto engines, would you expect to pay more for a factory replacement part of for a specialty shop's version? How about a ratio? I'll wager that custom car parts are almost indentically more expensive that stock for the same reasons. The smaller firm is making higher tolerance, more shiny, or better designed parts in much smaller runs. The economy of scale can't be avoided in any market.

    Not only are the parts more expensive per unit if all the reseaarch, improved alloy investments of materails, and specialized hand work used to combine them into a more torque tolerant engine- fewer units are eventually sold increasing the margin per unit to make money. You know what I'm describing, a few percent of millions is more than 10 percent of a few thousand.

    Last, (well, the last reason here) there is a premium value placed on some brands like Mercruiser, which is often a tad more expensive than other marined engines but isn't really proven to last longer, at least not in any data I've seen. This feature of marketing must reach some area of your own life? surely you're willing to pay for a so-called "better" this_or_that if you are more satisfied with the brand name?

    So to summarize and hopefully help at least to provide an answer TOWARD your original question; the reason(s) for much higher costs in marine world are the limited number of units, higher skilled labor costs [for the lack of production runs justifying robots], more torque resistant, higher load capable parts, built to tighter tolerances of more expensive grade materials, again in smaller relative quantities, and finally a limited number of competitors in a market that enjoys/experiences the name brand "value" inflation of fashion, snobbery, and perceived quality.

    I hope you won't abandon the forum for a misunderstanding of terms used in an online discussion of something as esoteric as relative costs! I'm sure that other posters feel the same and I think Tad, a designer in Vancouver -not sure- mentioned he keeps in mind the casual nature of our conversations to avoid feeling slighted or taking offense.

    well, my few cents on the basis for costs in the "marine" market place.

    cheers,
    kmorin
     
  10. cyclops
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    cyclops Senior Member

    The engine in my 19' bowrider is always loafing. Stock is a V6. I have a V8 of 5.0L 220 hp carb. Also known as a Chevy. I plane in 3-4 sec and do 54 alone or 50 with 4 people. The engine could be a auto engine and performance would drop MAYBE 20 %. 40 years ago all boats ran chevy pickup truck engines because their cams are marine cams in reality. New Nissan Titan V8's in their pickups HAVE a flat torque output from 1000 to 3800 rpm. Marine cam. Nothing really changes. PR people have larger testicles than anyone else and no one challenges what they print.
     
  11. gonzo
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    gonzo Senior Member

    I've seen marine engines replaced with automotive and the boat hardly got up on a plane. They don't have the low end torque. If you must, install a tow truck engine.
     
  12. PowerTech
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    PowerTech Senior Member

    atention filmdady you say you wont post again here.Why bother posting any whare else ,you may find somewhere else that will codell your ideas of a afordable cheap automotive engineroom.But there is no such thing.The marine environment is a unforgiving ***** that will distroy even the best of engines and parts.Even the best of equipment will and does fail rutienly it is the nature of the beast.If you do not go out batting a thousand you will not come home happy.This aint no playground.If you want to experement go ahead but it will not be a yacht or even a boat it will be a dreamers toy.A boat is made to drive you around in the sea.The sea is a son of a ***** on equipment of the highest quality.You can drive any piece of **** to the grocery store but Dont screw around with the ocean.Goonzo may rub you the wrong way he does me too every time he opens his mouth I smell gasoline but regardless of that he knows marine is marine.And why fawk with the B.S..If you want a boat get a boat If you want a Winbego get one of them why mix the two.
     
  13. ABoatGuy
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    ABoatGuy Member

    Remember HP, Torque and RPM are all related. Torque turns a propeller. If you intend to have an engine running at around half it's rated RPM, make sure you take a look at the HP or torque curves of the engine and determine if what you are getting at the reduced RPM is adequate for your needs. Reduction gears can improve the torque at the prop, but they aren't cheap.

    A lot to think about here. In the case of marine engines, much of this has been sorted out by the engine builder. The demands of a fuel delivery systems, cooling system etc. are much different on the road then in a boat. The few dollars you save up front could soon disappear from your bank account as you are forced to deal with the details.

    Many people have made road engines work, but I wonder how many have saved money.
     
  14. SAE140

    SAE140 Guest

    talk of not getting on the plane, and experimenting, and unreliable ...

    The basic brief was a displacement hull - so talk of planing is irrelevant.

    Experimental - hardly. A pro boat-builder of my acquaintance has been installing tractor and truck diesels in boats for years. Now with tens of thousands of miles under their keels. Admittedly, these have marine boxes.

    As it happens, I have a 1960's Morris Vedette in my shed. This is a marine gas engine/box similar to the Atomic 4. Engine is a low-compression job straight out of a delivery van. A few safety mods to the carb, and a mod to fit a Jasbco pump for the raw-water cooling - otherwise a completely standard engine. Nothing amateurish about these engines. Thousands were made, and many are still running today. We're talking about a standard 4-cylinder automobile engine here, rated at 8HP (approx. 25 bhp), with a slightly lower rating for continuous operation.

    For a thrust bearing - pull a CV axle off a European Ford RWD (Sierra or similar), then you've got a ready-made thrust bearing and housing, together with a pair of sliding CV joints to make lining-up with the donk a breeze.
    We've been using these for years now. Never a problem, or even a hint of one.

    If you've got money to burn - buy marine-tagged goods from your local rip-off chandlers. Otherwise consider making your own stuff.

    And safety ? The UK has the lowest per capita marine accident record in the world. Go figure.

    A lot of prejudice on this board.

    Colin
     

  15. gonzo
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    gonzo Senior Member

    Colin: post some numbers on price of modifications including time. I resent your insults about rip-off chandlers. It is not prejudice to point out that marine engines are already modified or designed for the intended use. The UK may have the lowest accident rate, I don't know for sure, but it is not by using amateur installations like you suggest.
     
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