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Old 02-01-2019, 10:12 AM   #81
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Originally Posted by makobuilders View Post
There have been a few comments here about the key to long engine life being keeping the oil clean with aftermarket bypass filters, Gulf Coasts, centrifugal polishers, etc.

However I've always thought that just running the engine properly, monitoring EGT and sticking to the manufacturer's recommended oil change intervals should be good enough, without having to resort to expensive aftermarket items or synthetic oils.

Is there really some magic to these aftermarket items?
The items you mention and others are typically designed or used to address a specific issue. If everything is ok, clean oil and fuel, good maintenance, then extras likely not of value, but to address specific issues, they are a bit magical.
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Old 02-01-2019, 10:18 AM   #82
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Interesting thread. Got me thinking though, has anyone here actually worn out a 4 stroke diesel or gas engine in a recreational boat? I don't want to include catastrophic failures, just simple wear from normal use with proper maintenance. I did not include 2 stroke diesel engines because they do seem to wear out faster, but are easy and cheap to rebuild. I also did not include 2 stroke gas engines because they often fail due to inadequate oil in the gas/oil mix.
How many human beings do you know who just wear out? We don't die from miles or age. We have one or more parts or organs that fails on us.

Wear leads to catastrophic failure. You can't ignore it. 2 strokes don't just wear out either, something goes on them and then other damage occurs. So, 4 strokes don't fail simply from old age, but they do fail from one or more parts failing due to use or age.

I recall seeing "blown" outboards when I was young. Often they'd have something like a broken crankshaft and it would be amazing how parts of the engine would look almost brand new. But the engine was trash at that point.
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Old 02-01-2019, 10:38 AM   #83
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From a well respected marine engineer...

"How many angels can dance on the head of a pin?

Unless you measure propeller shaft torque, rpm fuel flow, and SOG in real time and use that data to calculate propulsive efficiency (fuel burned vs distance traveled) there is little point in the ongoing discussion.

By its nature, a propeller will impose a widely varying load on the prop shaft/engine. It varies with sea state, wind, and speed through the water, plus depth of prop immersion. It varies rapidly and moment by moment and only over a period of hours can a useful average be obtained and that is only really useful for boats making long enough passages for such data to really matter.*

The discussion is just about as useful as the anchor discussion and singles vs twins.*"
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Old 02-01-2019, 11:54 AM   #84
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I was wondering when the marine engineer would chime in. Nice to know RickB is still alive and well.
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Old 02-01-2019, 12:03 PM   #85
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Wow!

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Originally Posted by Mischief Managed View Post
Interesting thread. Got me thinking though, has anyone here actually worn out a 4 stroke diesel or gas engine in a recreational boat? I don't want to include catastrophic failures, just simple wear from normal use with proper maintenance. I did not include 2 stroke diesel engines because they do seem to wear out faster, but are easy and cheap to rebuild. I also did not include 2 stroke gas engines because they often fail due to inadequate oil in the gas/oil mix.



In my immediate family's collection of vehicles (that I maintain) we have:


One turbo diesel V8 pickup with 6000ish hours (209,000 miles) This one has an hour meter which is how I can easily estimate hours on the other vehicles based on miles.


Two 4 cylinder gas-powered with 6000ish hours (200,000 to 220,000 miles)


Two V6 gas-powered cars with 4000 to 5000 hours (145000 to 180000 miles)


One 4 cylinder sport motorcycle (Ninja ZX9R) with 3000ish hours (111,000 miles)


One V8 gas-powered boat with 1000 hours (real hour meter on this one too)



All of them run like new. I have never actually worn out an engine on anything and I keep stuff a really long time.
You are my new hero. That you keep the vehicles so long is amazing in this current throw-away society.

Gordon
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Old 02-01-2019, 12:06 PM   #86
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Originally Posted by makobuilders View Post
There have been a few comments here about the key to long engine life being keeping the oil clean with aftermarket bypass filters, Gulf Coasts, centrifugal polishers, etc.

However I've always thought that just running the engine properly, monitoring EGT and sticking to the manufacturer's recommended oil change intervals should be good enough, without having to resort to expensive aftermarket items or synthetic oils.

Is there really some magic to these aftermarket items?
I don't recall that anyone has suggested that bypass filteration is a key to much of anything other than cleaner oil, but I might have missed it. The reduction of wear with cleaner rather than dirtier oil seems more like physics than magic, but you're quite right - "good enough" is, well, good enough for some of not the everyone.
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Old 02-01-2019, 12:11 PM   #87
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Saying that fuel used is an indirect measure of torque on a diesel engine is in some sense backwards. It is the fuel injected that causes the torque, not the other way around. The torque map in the ECU of a modern common rail engine is very accurate, the engine operation absolutely depends on it being so.
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Old 02-01-2019, 12:26 PM   #88
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The quote didn't say that torque is a measure of fuel burn. But a torque measurement is required to establish actual horsepower at a given rpm (impossible to measure HP directly). Do these ECU engines measure torque? If they don't then a BMEP approach (FF's post) is not in the cards.
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Old 02-01-2019, 01:14 PM   #89
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Seems like a circular discussion. Torque is not measured. Fuel flow is not measured.

ECU has rpm measurement, crank position sensing, charge air measurement, along with various temps and pressures. Input rpm request from helm. Output from fuel map is injector open times, timing, rail pressure, etc.

But in the above algorithm, the data points can be compared to data taken when the (or same model) engine was on the factory dyno. On the dyno they DO measure torque and fuel burn with lab quality equipment. Those dyno data are stored in the ECU.

So where ever you are operating the engine, ECU can look up in its tables and see what the torque and fuel burn should be based on the dyno data and current operating parameters. That is what is displayed. No need to actually measure. Measuring torque and burn directly requires expensive and sensitive equipment.
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Old 02-01-2019, 05:07 PM   #90
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Seems like a circular discussion. Torque is not measured. Fuel flow is not measured.

ECU has rpm measurement, crank position sensing, charge air measurement, along with various temps and pressures. Input rpm request from helm. Output from fuel map is injector open times, timing, rail pressure, etc.

But in the above algorithm, the data points can be compared to data taken when the (or same model) engine was on the factory dyno. On the dyno they DO measure torque and fuel burn with lab quality equipment. Those dyno data are stored in the ECU.

So where ever you are operating the engine, ECU can look up in its tables and see what the torque and fuel burn should be based on the dyno data and current operating parameters. That is what is displayed. No need to actually measure. Measuring torque and burn directly requires expensive and sensitive equipment.
No it's not circular. Obviously ECU engines work. My remarks were specifically in response to FF's comment about using the BMEP charts for engine operation. Todays ECUs basically load prop chart(s) in memory for more precise engine control. But they don't have the entire BMEP matrix loaded up, nor can they send the engine to the best point on that matrix to achieve a desired hull speed. Impossible to do with a fixed pitch prop. Add a variable pitch prop and the BMEP scenario becomes realistic. Instead of an rpm demand, the parameter input by the operator would likely be hull speed. The prop computer and the engine computer would talk to one another and arrive at the best place to take the engine/propeller combination. I don't believe that could be done without actual torque as an input parameter. For one thing torque limits on drive line components would have to be respected. This is a common scenario with turbine helicopter drive trains.
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Old 02-01-2019, 05:49 PM   #91
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The ECU absolutely sets the injection events to the best point in the matrix. It is absolutely possible to optimize parameters for the given engine operating point. Fixed pitch or CPP.
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Old 02-01-2019, 06:43 PM   #92
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The prop computer and the engine computer would talk to one another and arrive at the best place to take the engine/propeller combination. I don't believe that could be done without actual torque as an input parameter. For one thing torque limits on drive line components would have to be respected.
This is done in every modern diesel truck. The engine ECU and the powertrain PCU are in real time communication with all parameters. The torque estimate from the ECU is highly accurate for any operating condition. Together they select gear ratio, torque, and rpm. One of the not so well kept secrets is your Cummins in your RAM truck, while rated at 1000 ft lbs, is not allowed to do that very often due to drive train limitations. In fact on the QSB chart note that the torque falls off as you near max rpm, that is an ECU imposed limit to keep cooling and other things in check. The miracle of computer controlled common rail engines is every operating parameter is just a few lines of code.

On a boat you do not have this freedom as prop and transmission are usually fixed. You have an RPM lever and everything else is a dependent function.
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Old 02-01-2019, 07:20 PM   #93
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Precisely. No question ECUs can set whatever parameters are requested (SKI's comment above). But the current RPM demand control architecture does not and cannot allow for full optimization per the BMEP chart. A variable pitch prop and the appropriate fuel control architecture probably could. I'm still thinking about the use of a torque estimate versus an actual measurement particularly given the "fluid" operating environment for the propeller.
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Old 02-04-2019, 02:32 PM   #94
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Running Diesels at Ideal Loading for Longevity

Makes sense.

And after observing good fuel and mechanical maintenance practices, Oil is Everything Else.
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Old 02-04-2019, 03:41 PM   #95
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I'm sorry, but I way disagree with Mr. Zimmerman. He is basically advising that one should have an engine 3 times larger than is necessary. As if one needs a car that must do 210 mph if one wishes to cruise at 70 mph! Preposterous!
If you think about it, a genset often operates near full load for hours at a time and if well maintained, 12 to 15 thousand hours is not an unreasonable figure for a genset's lifespan. Our Onan passed 19,000 hours and was still running well, though maintenance was becoming a problem with things like freeze plugs and other cooling system parts failing.
Diesels love to be run at their rated continuous operating speed with the correct load. Its all about matching the boat's hull shape and weight, the prop, the trans reduction ratio, and engine hp correctly to get the maximum performance and longevity out of any marine engine. The worst thing one can do is just assume that the former owners propped the vessel correctly. Overloading at low RPMs will kill an engine faster than anything other than a complete lack of use and maintenance, and the less one uses any engine, the more maintenance it will require.
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Old 02-04-2019, 04:13 PM   #96
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I'm sorry, but I way disagree with Mr. Zimmerman. He is basically advising that one should have an engine 3 times larger than is necessary. As if one needs a car that must do 210 mph if one wishes to cruise at 70 mph! Preposterous!
If you think about it, a genset often operates near full load for hours at a time and if well maintained, 12 to 15 thousand hours is not an unreasonable figure for a genset's lifespan. Our Onan passed 19,000 hours and was still running well, though maintenance was becoming a problem with things like freeze plugs and other cooling system parts failing.
Diesels love to be run at their rated continuous operating speed with the correct load. Its all about matching the boat's hull shape and weight, the prop, the trans reduction ratio, and engine hp correctly to get the maximum performance and longevity out of any marine engine. The worst thing one can do is just assume that the former owners propped the vessel correctly. Overloading at low RPMs will kill an engine faster than anything other than a complete lack of use and maintenance, and the less one uses any engine, the more maintenance it will require.
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Old 02-04-2019, 04:51 PM   #97
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I've been operating diesel engines for more than 5 decades, from single cylinder air cooled portable ones to a few with single piston displacements larger than the cabin many on here sleep in. Never once ran any of them @ 35%. Heck, on many diesel engines, 35% just barely gets the oil and water circulating correctly.
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Old 02-04-2019, 05:04 PM   #98
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That million miles average for semi engines translates to around 20,000 hours or around 100 years the way most people use their boats.
Exactly.
Which is why i'm so amused by the constant fascination with engine life on TF.

It's probably the least costly aspect of boat ownership.
I'm asked often, with all the cruising i do, 5,000 hours in 5 years, if i'm planning on rebuilding my engine?
Ha !
At a 1,000 hours a year, 20,000 hours will arrive when i'm 90 years old.

As long as a boat owner has a modicum of understanding how engines work (excessive heat or cold is bad), the engine is the least of their worries.
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Old 02-04-2019, 05:14 PM   #99
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"Diesels love to be run at their rated continuous operating speed with the correct load."

"Never once ran any of them @ 35%. Heck, on many diesel engines, 35% just barely gets the oil and water circulating correctly"

Two quotes on the same subject and both may be true, but only for some engines.

Take Yanmar's liberal definition of continuous operation at 200 rpm off of top. If you do that for long with some of their 70-80 hp per liter engines, they will be lucky to last 2,000 hours. But do that with a John Deere or a Cummins continuous duty definition (most Cummins continuous duty engines are rate at 1,800 rpm for genset use) and you will be ok for 5,000+ hours.

Same thing with the second quote. I ran my Yanmar 370 hp engine at 1,600 rpm or about 55 hp or 15% load and it is quite happy there. But most sailboat engines as well as Krogens and Nordhavns run at 50% all day long.

That is why the concept of running at a recommended pct load is pure BS.

A much much better way of looking at it is Tony Athens rule of thumb (supported by various engine builders data sheets) that 35 hp per liter is a good maximum continuous cruising load. And that rule is only good for high performance turbo charged engines. Many NA engines won't make that at full load.

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Old 02-04-2019, 05:38 PM   #100
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Exactly.
Which is why i'm so amused by the constant fascination with engine life on TF.

It's probably the least costly aspect of boat ownership.
I'm asked often, with all the cruising i do, 5,000 hours in 5 years, if i'm planning on rebuilding my engine?
Ha !
At a 1,000 hours a year, 20,000 hours will arrive when i'm 90 years old.

As long as a boat owner has a modicum of understanding how engines work (excessive heat or cold is bad), the engine is the least of their worries.
I ran a CAT 3208, which is supposed to be a throw away engine due to the lack of wet sleeves, for just over 1,000,000 miles and it was going strong when I sold the truck it was in. In cruising terms, that's around 20,000 hours. The 3306 I have in Delfin is reputed to be a 50,000 hour engine if you follow CAT's maintenance and load advice, which is > than 30% load. I'll sell her to your great grandchildren and they'll still be able to cruise her for a couple of decades.

IMHO, the 35% load recommended by an expert like Zimmerman seems about right, as long as you spend some time every day or so heating the engine up to minimize slobber and carbon buildup.

I've installed bypass filters and use synthetic oil not because I think that if I didn't my engine would fail, but for the same reason I clean the attic now and again. Pride of ownership, which to me translates to trying to take good care of my toys.
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