Marine (ized) engine horsepower loss over time

Discussion in 'Gas Engines' started by Red Tide, Oct 19, 2009.

  1. Frosty

    Frosty Previous Member

    Mercruiser engines used to be Chevrolet before they were Ford, a lot less than half a century ago.
     
  2. CDK
    Joined: Aug 2007
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    CDK retired engineer

    You are partly right and partly wrong.
    I believe the purpose of forums like this is that people can give their opinions. You cannot expect me to give someone else's opinion. That I present mine in a matter-of-fact manner seems to bother you, but maybe I see facts where others do not.

    Over the years I also have been a customer of this Jukebox/Bowling alley company. I've had 6 Mercruiser engines and 4 Mercury outboards. In fact I still use a 5 hp that serves me very well. Future buyers I advise to buy one from Tohatsu: the price is much lower and you get the same product, but in dark gray instead of black. Fact or opinion? You figure it out.

    But back to the topic.
    From personal experience, albeit long ago: I bought a brand new boat with a Merc V-8, 12 months warranty, service done by Mercruiser approved people. After 13 months and approx. 60 engine hours (that's normal for pleasure craft, they do not expect you to really use it), the engine went up in smoke. One piston traveling free, one head cracked and the camshaft severed in two almost equal pieces. Warranty claim refused, but the insurance did pay (almost) everything and I got a new, even more powerful (?) engine that also had a violent death, but not during my ownership.

    There are numerous examples to show that commercial companies claim unrealistic performance, because the truth would substantially drop their sales. But in the industrial field things are quite different: you don't get away with such behavior. That is why I have more faith in industrial ratings.

    About the fuel pump.
    I never provided the link you asked me for; bad habit maybe, but I rarely ever do that. The brushless Japanese pump I took apart and reassembled is submerged in a large fuel tank filled when the price was right, so I can't even show you a picture....
     
  3. broke_not
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    broke_not Junior Member

    "Maybe I see facts where others do not."

    Seriously, were you giggling as you typed that? Forums are chock-full of opinions, but problems can arise when people go to those forums to get information....and the information turns out to be inaccurate. The simplest solution, is when you offer up something that's your opinion, identify it as such.

    "It's my opinion that <insert opinion here>"

    Don't start out with a matter-of-fact declaration.

    Then when someone opposes or challenges your opinion, don't shovel on a bunch of *bs*. That's where the "baffle them with bs" phrase came from.

    In closing, I'd once again like to point to your "Brunswick shareholder" comment. It speaks more clearly about your methods than I ever could.

    Cheers.
     
  4. apex1

    apex1 Guest

    Hmm, you should make that your motto too!

    Of course CDK was right, these old iron pigs live for minutes only, when they have to crank out the hp they are advertised to deliver. That IS fiction.

    And talking BS is, when one tells us industrial engines are set at 4000 rpm. That is the sheer nonsense. There are so many different applications, that you can find the same engine with settings from 1500 to 5000 rpm easily. In marine setup the cont. output is the one that counts, as mentioned above.
     
  5. broke_not
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    broke_not Junior Member

    They'll last for "minutes only" when cranking out their advertised hp?

    Really?

    And even if they did, at what point does that advertised hp number become "fictional"?

    FWIW, I never said industrial engines were "set" to 4000 rpm, I said they have their hp "rated" at a lower rpm. Manufacturers of industrial equipment need to know when choosing a powerplant what it's output will be closer to the rpm range it will see in the use they have in mind for it. Like I posted earlier, it really makes no sense to advertise, (by the engine manufacturer), what an industrial engine's "peak" hp rating is.....because in the applications it will end up in, it won't be seeing that rpm ever anyway. I happen to maintain a fleet of such industrial equipment, and the equipment manufacturers don't give a hoot what a 3.0 GM four, (or whatever the case may be), will produce for a peak number. They're concerned about the power level at the rpm it will see in normal operation. If the directly-coupled hydrostatic pump for instance is designed to be most efficient at 3000 rpm, they'll choose an engine that produces the hp desired at that engine speed. In a genset, if the directly-coupled generator head needs to spin at 1800 or 3600 rpm to operate correctly, then the genset manufacturer will look to the engine supplier for an engine that produces the required amount of power at that rpm.

    In non-industrial applications in which the rpm range varies as widely as it does, a peak number is more relevant.....because it's what everyone uses. Imagine all of the confusion there would be if it were done otherwise. You can't market your product against the competitor if you're rating your products differently. As a customer, you can't comparison shop if the products are rated differently.

    Simply put, there's nothing "fictional" about the ratings of industrial or non-industrial engines. They're rated differently, for good reason. It doesn't make either rating "fictional".

    Please provide some of these easy-to-find examples of industrial engines with 5000 rpm "settings". And by "settings", I mean an application in which an equipment manufacturer designed their machinery in such a manner that they had to send their engine supplier a spec for an engine that would be turning at 5000 rpm all day long. That certainly seems to directly oppose your earlier statement about engines only being able to live for a few minutes under those conditions...


    ;-)
     
  6. CDK
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    CDK retired engineer

    It seems I struck a nerve there.
    But honestly, that could in my opinion be the only sound reason for defending the merits of these engines. Although since my retirement I cannot afford a Mercedes ML anymore, I helped out Daimler-Benz with a considerable sum. Solid people, never caught them telling lies, so of course I would defend them.

    Look at Mercruiser 2009 on the web: they offer the patented TKS technology for a variety of hopelessly outdated fuel wasting carb engines that were banned by legislation for road use years ago. TKS means Turn the Key to Start: a truly great invention, why didn't I think of it. Much easier than saying all these prayers most boat-owners need to wake up their horses.

    Ask them for a torque/power curve (you won't find any on their websites) and they will reply that it is proprietary information and company policy not to disclose such information. I know for sure because I did ask. It is like asking the guy with the longest dick on the block to pull his pants down. If you have nothing to hide, like Cummins, Steyr or VW, what reason for secrecy could there be? Confusion for sure.

    To some, doing business means buying as cheap as possible and selling to ignorant customers at the maximum price, all tricks allowed. We live in a world of tricksters and conman going at great length to make us part from our money. Your car stereo cannot produce 500 watts while drawing only 4 Amps, your 1000 watt speakers start smoking at 10% of that power and your laptop doesn't clock a 4 Ghz or even 10% of that. Compared to that, the Merc 250 doesn't do so badly during the first few hours.
     
  7. broke_not
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    broke_not Junior Member

    Okay, so then when an engine manufacturer provides a dyno chart for an engine that clearly shows what the produced amount of power is, then how is the provided number "fictional"? Your examples may very well be exaggerated specs designed to fool consumers, but then again, when they exaggerate, they aren't providing any proof about where those numbers came from....are they?

    Can't fault you for "defending them", but it is a little ridiculous to then assume that anyone with anything to say that doesn't agree with what you happen to believe must have some "motive" other than wanting to clear the air and provide some accurate information.

    ;-)
     
  8. Red Tide
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    Red Tide Junior Member

    In the great majority of installations as rigged will the engine survive as "advertised"? If not, it seems fictional to me. If so, then ok understanding the rating is for occasional use. What I mean is what happens if a typical boat owner runs the engine at 4,000, 4,500, or 5,000 RPM for 30 minutes once a week (while cruising the majority of the time at 3,000 RPM or about 1/2 output) What will a little bit of running at the engine's higher horsepower RPM range or running a little bit at WOT do to the average mercruiser gas engine?
     
  9. Frosty

    Frosty Previous Member

    Ive blown more American iron than any other engines. Be it cars or boats.
     
  10. Red Tide
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    Red Tide Junior Member

    I suppose you have to look at the warranty as the boundary of fact and chance... 1 to 3 years is what they're warrantied for. Beyond that... (scary if you take the engine cost and divide it by the 1 to 3 years of use)
     
  11. tuantom
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    tuantom Senior Member

    Used to have a Ford 351w in my dad's boat that my brother and I'd beat up pretty regularly back before I knew how to pay for things. Was rated at 250 HP and we'd try to use all that as often as possible - WOT @ ~4300 rpms for 15 or 20 miles was common enough (Gas was cheap in the 90's). It never blew up - though it was mighty tired after about 18 seasons. My brother's been keeping that up with his own boat with a Mercruiser 260 for the last 7 or 8 years now - though it's been tempered a bit by higher gas prices.

    I've personally seen many examples of small block and especially big block engines being a lot more durable than being said here - Comparable to a Mercedes? I'd guess probably not; but I probably could build 5 of them for the cost of one Mercedes.
     
  12. powerabout
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    powerabout Senior Member

    i have seen a 260, 330, 370 Mercruisers with dry headers on a dyno and they made
    260 330 and 370 FTLbs of torque and hence the horsepower numbers were less.
    Maybe we read the numbers backwards downunder.....?

    I do know the above info led to a court case (in OZ )with a boat builder when he found out a 260 isnt 260hp.
    (Nothing to do with the project I was involved with but the dyno shop supplied the info)
    It was settled but I never found out and Merc wouldnt say?

    On the old K&O hydraulic dyno's a 260 Mercruiser and the old 225 merc outboard pumped nearly the same pressure?
     
  13. Yellowjacket
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    Yellowjacket Senior Member

    Most if not all reciprocating engines, be it gas or diesel cannot operate at wide open throttle for any extended period of time.

    If you go to the MAN website and look at the ratings, typically they rate the engine at a given power, but then in the fine print say that it is only supposed to be used for no more than 1,000 hrs per year and only for 20% of the time at full power and the rest of the time it is assumed to be used at 50% power. The warranty for the engine is 24 months. If you take it to mean that the engine might last for about 400 hours at full power you are probably pretty much on the money.

    I am not picking on MAN, they are simply typical and I had data on their engines. I am sure that they make a good engine, but ALL reciprocating engines have their limitations. They can all put out more power for short periods of time than they can for a long time. When you select your engine you simply have to figure how YOU are going to use it and decide on a power rating that is appropriate for YOUR application. If you need more power you can't run the weee weee out of an engine and expect it to live.

    I have disassembled an aircraft engine that had 2,300 hours on it at 75% and greater power and everything in the engine was just plum worn out. Marine engines are like aircraft engines in that they can be run at high power levels for extended periods of time, and that is simply severe service. You can't expect an auto engine that can make 350 hp at 6,000 rpm in a car to live long if you lock down the throttle in a boat. Nobody is lying about the ratings, the engines make the power they advertise, but you can't run ANY of them at that power and expect them to live a long time.

    Keep the amount of time at max rated power down to below 20% (a typical "pleasure craft" rating) and they will last a long time. But if you underpower your boat and bend the throttle over and expect the engine to live very long you are kidding yourself.
     
  14. CDK
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    CDK retired engineer

    That is very interesting.
    Aircraft engines are not the topic here, but now that you mentioned it, they are very conservatively rated for obvious safety reasons. Extremely well built from superb materials, they should last much longer than 2300 hours.
    Could it be that the one you took apart was used for other purposes? Normally an aircraft engine is disassembled, inspected and reinstalled quite frequently to obtain certification for the next 12 months.

    I remember that jet engines at run-up were allowed to rev up to 110% power, sometimes even more.
     

  15. Yellowjacket
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    Yellowjacket Senior Member

    Most normally aspirated reciprocating aircraft engines have an FAA rated Time Between Overhauls of about 2,000 hours. You can look it up on the type certificate data sheets that are on the FAA web site. At that point they are pretty much ready for an overhaul. Typically the valves and valve seats are showing wear, the pistion rings and bores are worn and there is a lot of burned oil in the ring grooves. All of this is a function of time at temperature and load. Generally the feeling is that if you run much past TBO you are asking for trouble. Very seldom do general aviation engines such as a Lycoming or Continental run much past TBO, and many never make it that far. Most are run at 75% power with higher power settings for a few minutes (like five or less) at takeoff power. If you loaf around you might go further, but that is about the typical life expectancy between rebuilds.

    Turbines are another matter entirely. Depending on how the turbine was rated, there may or may not be the capability to run the engine at higher power for short periods. The life of uncooled hot section components typically degrades by half for each 25 degrees F hotter that you run it. That is, run it 25 degrees hotter and the life is reduced to half of what it was at the rated temperature, run it 50 degrees hotter and the life is 1/4. The opposite is also true, if you run it 25 degrees F cooler, the life will double, 50 degrees cooler and the life is 4 times longer and run it 100 degrees cooler and the life is 16x greater. Typically a slight derate of 50 to 75 degrees for use in a boat or in ground power applications results in a turbine that will last pretty much forever.

    Ratings of takeoff power in aircraft turbines are very different than turbines used on the ground. Often there are limits that are applied to a turbine in the takeoff mode to limt the power in the fan or gearbox. In many cases the engine is running harder at cruise due to altitude effects, than it does on the ground or at takeoff, consequently, there is no real comparison with reciprocrating engines other than if you run it too hot for too long the life goes into the toilet.
     
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