Gas vs. Diesel

[smitty477]

"I will go out on a bit of a limb here and say that Rick has had more hands-on, diagnose-it, fix-it experience with more types of marine diesels than anyone else on this forum. His current business is selling and installing a marine generator exhaust system of his own design to mega-yacht owners and operators all over the world.

Asking him to list all the engines he has run or is very familiar with would take him a day of typing to answer and he most certainly would prefer to make more productive, or at least more interesting, use of his time."


So maybe pick one common type of engine that used by us "normal" folks recreationally and try and help folks on this forum learn how we can load up those engines and still not loose any reasonable engine life.
If not then why bother to post at all?

 

[CPseudonym]

Well, a lot of people on this forum don't know who Rick is or what his experience level is, which as longtimers know is far greater than most if not all of the participants in this forum. While "Yawn" may mean something to people who already know Rick, it may not to people who don't such as Smitty477.

Sounds like he knows precisely who he is to me...

 

[smitty477]

"Sounds like he knows precisely who he is to me... "


Hello Craig - Looks like you have 6,495 posts so maybe you can tell me what that means perhaps?

 

[siestakey]

Well, a lot of people on this forum don't know who Rick is or what his experience level is, which as longtimers know is far greater than most if not all of the participants in this forum. While "Yawn" may mean something to people who already know Rick, it may not to people who don't such as Smitty477.

As you were not the one who typed the two paragraphs, nor did you have to read them, I'm not quite sure what you're heartburn is all about. Although perhaps your ISP contract charges by the word your device receives, in which case I guess I'd get upset over posts I wasn't interested in, too.

Marin

As with in life we are all so different and so diverse If B and Wife want to let me or others know who they are that is fine.

I do not just come on here for the great information I get from the members but also relaxing to me

At the same time others want nothing but knowledge no friendship etc

So I take you and others for what I find them to be on the forum

Several on the forum I have become friends with and one actually went out of his way to meet my wife and I for a drink in Spain a couple months ago

Another sent supplies to help out a mission project I went on in the Czech Republic

As we all know in this forum I am no word smith but I do enjoy most of your posts and most Bs post

I like to just let people be what they want to be here and enjoy

Alan

 

[ssobol]

IMO - I think that the gas vs. diesel engine distribution in boats mirrors the distribution in land based motor vehicles for exactly the same reasons.

Larger, stronger, longer range prefer diesel.

Smaller, quicker, shorter range prefer gas.

I also think that the safety concerns of gas vs. diesel are known and manageable (we do it in our cars every day) and don't really affect the equation very much at all.

 

[RT Firefly]

 

[cool beans]

Yes there are certainly issues with keeping all that high tension circuitry doing its job in a damp, corrosive, salt water marine environment.

A little PM goes a long way though. Dielectric grease on the plug boots, sealed marine dizzy cap, anti corrosion spray on the ignition coil terminals. . .should be trouble free. Beginning of every season, these things need to be checked and touched up. Clean and gap your plugs, touch up the dielectric grease, light emery cloth on the rotor and cap terminals to get the carbon scoring off, check your ignition coil connections and touch up. If you fogged the motor before putting it up for winter, and either drained the tank or filled it up and treated it, you shouldn't have any running issues.

Of course, all the people i have helped over the years with their car and boat engines. . .never seem to do any of the above

When you guys talk about 10,000 hour+ life expectancy. . .are you referring to the entire motor as a power plant or just the short block? My diesel engine experience is all automotive. People on FTE would have 500k+ miles on the short block, but they'd have been thru 2-3 sets of injectors, 1-2 injector pumps, rebuilt the heads (and ready for another), new exhaust manifolds, 2 rebuilds on the turbo (or replaced). . .

Depending how long the peripherals last could make the difference between gas and diesel to me. Hypothetically, if over ten years of ownership of a pair of already 35 year old perkins, you still have to at least replace the exhaust manifolds, turbos, intercoolers, a head job, injectors, and fuel pump(s). . .probably to the tune of $20,000? If 150 hrs a year use, that's only 1500 hrs. . .maybe 3 sets of risers and manifolds for the crusaders? $2,000? I'll even give you a pair of long block 454's replaced in that time. . .$7,000. This is off the top of my head, but am I missing something?

LoL, just how much more gas does a 454 @ 7 knots burn vs a diesel

 

[ksanders]

I will go out on a bit of a limb here and say that Rick has had more hands-on, diagnose-it, fix-it experience with more types of marine diesels than anyone else on this forum. His current business is selling and installing a marine generator exhaust system of his own design to mega-yacht owners and operators all over the world.

Asking him to list all the engines he has run or is very familiar with would take him a day of typing to answer and he most certainly would prefer to make more productive, or at least more interesting, use of his time.

Actually the question is very valid.

Rick deals in mega yachts. He is very knowledgable regarding them. That said when posting as a subject matter expert, you need to be open to questions regarding the basis for that expertise, and not on mega yachts. Nobody here owns a mega yacht, we own recreational boats 95% are 50' or less.

He quoted a 1600 horsepower engine. nobody here owns one of those, or anything close. the engineering standards and the life expectancy probably cannot be compared with my 5.9L cummins at 330 hp.

 

[Marin]

Nobody here owns a mega yacht, we own recreational boats 95% are 50' or less.

He quoted a 1600 horsepower engine. nobody here owns one of those, or anything close.

Rick's owned boats just like ours. He has given me in the past valuable information and understanding about how the fuel injection pumps and governors on our FL120s work, information about our Onan MDJE Jurassic Edition generator, and so forth.

I'll leave it to him to spell out his range of engine experience if he wants to. I simply wanted to point out to someone who I assume had never heard of him that, unlike a lot of people on this and similar amateur user internet forums, Rick knows a hell of a lot more than the average forum user would assume if they didn't know him already.

(Sorry psneeld, there's two paragraphs again. Hope they didn't break the bank......)

 

[RickB]

Actually the question is very valid.

Rick deals in mega yachts.

Rick makes a living from megayachts. Those boats use generator engines the same makes and models as many if not most toy boat propulsion engines.

Over a career of working on boats from 5 hp single cylinder diesels to 60,000hp 12 cylinder 2 stroke diesels, 32,000 hp steam turbines down to 10hp recip steam engines and a host of gassers from make & break to electronic ignition, diesel electric to direct reversing engines of modern build to those nearly a century old and everything in between I have to say that your conception and misrepresentation of my background is as nonsensical as some of the material posted in this thread.

How about just concentrating on the content of the posts and get past your prejudices about the source and all readers might learn a bit.

 

[ksanders]

Rick makes a living from megayachts. Those boats use generator engines the same makes and models as many if not most toy boat propulsion engines.

Over a career of working on boats from 5 hp single cylinder diesels to 60,000hp 12 cylinder 2 stroke diesels, 32,000 hp steam turbines down to 10hp recip steam engines and a host of gassers from make & break to electronic ignition, diesel electric to direct reversing engines of modern build to those nearly a century old and everything in between I have to say that your conception and misrepresentation of my background is as nonsensical as some of the material posted in this thread.

How about just concentrating on the content of the posts and get past your prejudices about the source and all readers might learn a bit.

Thanks You Rick, I did not have a problem and do not. Smitty477's question was valid, and thanks very much for answering.

 

[ksanders]

What I am seeing in the field is that high horsepower to displacement diesels are having a much shorter useful lifespan than their owners, and the "diesel legend of longevity" would indicate.

This differs from the same engine block being used in a generator application. In a generator application for example we generally see between 20 and 25,000 hours of operation prior to rebuild or replacement. In a pleasure craft application we are seeing many of the high horsepower to weight engines needing rebuild at 2,000 hours or thereabouts.

The root cause of many or modt of these short lifespans is not known or understood by the owners. We could debate those reasons forever. What is difficult to debate is that high horsepower to displacement engines are experiencing shorter than anticipated lifespans.

What I have noted is that high horsepower to displacement engines that are run at high power ratings, for example engines whos owners run up on plane much of the time are much more frequently experiencing shortened engine life.

This data is not drawn from anything scientific. It is drawn from owner interaction both in person and on forums. I hve had communications with literally thousands of pleasure boat owners over a period of over a decade and have noted this trend in high horsepower to displacement engines.

I have also myself replaced four Cummins 6Bta5.9 330 HP engines in boats I have owned or was buying.

 

[BruceK]

Kevin, surely much of the longevity of the standing generator engine comes from never getting cold. Taxis are an example of high mileage engines when compared with privately owned and used identical model cars.
The sub question would be comparing high HP output diesel engines with low output engines, engines with and without turbochargers, etc. I wonder how long VW/Skoda/Audi engines with turbo and supercharger are likely to last. All things other being equal, squeezing more power out of less ccs/ci seems likely to result in faster wear.

 

[BandB]

What I am seeing in the field is that high horsepower to displacement diesels are having a much shorter useful lifespan than their owners, and the "diesel legend of longevity" would indicate.

This differs from the same engine block being used in a generator application. In a generator application for example we generally see between 20 and 25,000 hours of operation prior to rebuild or replacement. In a pleasure craft application we are seeing many of the high horsepower to weight engines needing rebuild at 2,000 hours or thereabouts.

The root cause of many or modt of these short lifespans is not known or understood by the owners. We could debate those reasons forever. What is difficult to debate is that high horsepower to displacement engines are experiencing shorter than anticipated lifespans.

What I have noted is that high horsepower to displacement engines that are run at high power ratings, for example engines whos owners run up on plane much of the time are much more frequently experiencing shortened engine life.

This data is not drawn from anything scientific. It is drawn from owner interaction both in person and on forums. I hve had communications with literally thousands of pleasure boat owners over a period of over a decade and have noted this trend in high horsepower to displacement engines.

I have also myself replaced four Cummins 6Bta5.9 330 HP engines in boats I have owned or was buying.

What size and what brands of engines are you basing this on? Where are you seeing it? Are these recently manufactured engines?

 

[ksanders]

What size and what brands of engines are you basing this on? Where are you seeing it? Are these recently manufactured engines?

Cummins B series mostly

Some Yanmar

Some Volvo.

Pretty much distributed to how popular these engines are, so it's not brand specific.

I'm not even saying it's the engines fault. I have no clue. At high engine loading one little thing goes wrong with for example the cooling system and the engine is toast in a matter of seconds.

I have seen that myself with my own eyes.

 

[BryanF]

I am not surprised by failures in engines at higher speeds and loads. I keep looking at the small Cummins at 330 horse power and wonder why its' big brother at 14 liters is only 360 horse power. Seems to me that the less stressed unit will last longer. Kind of like top fuel dragster engines. They might make 4000 horse power but they don't do it for long.
The 14 liter cummins that was sitting beside me last week has fished for 22 years with two sets of injectors and a fuel pump in that time. I just don't see the small version lasting that long.

 

[BandB]

Cummins B series mostly

Some Yanmar

Some Volvo.

Pretty much distributed to how popular these engines are, so it's not brand specific.

I'm not even saying it's the engines fault. I have no clue. At high engine loading one little thing goes wrong with for example the cooling system and the engine is toast in a matter of seconds.

I have seen that myself with my own eyes.

Well, our Yanmar's don't fit then. We have a 4JH4 which is 100 hp, 121 cu. in. and a 4BY3 which is 150 hp, 122 cu. in. Not in displacement boats though.

I often wonder if some of the issues result from poor choices by builders in matching engine and boat and use.

 

[RickB]

I often wonder if some of the issues result from poor choices by builders in matching engine and boat and use.

It might have more to do with owner expectations. When you buy an engine you are buying power - horsepower hours to be exact.

Think of the engine as if it is a fuel tank. If you want to extract a large amount of power in a relatively short period you will empty that tank earlier.

All the talk about reliability is just a circle jerk. As should be obvious by now unless the issue is a design or material problem (which is typically corrected by the manufacturer in very short order) reliability is practically always a product of owner/user knowledge and technique.

 

[FF]

"This differs from the same engine block being used in a generator application. In a generator application for example we generally see between 20 and 25,000 hours of operation prior to rebuild or replacement. In a pleasure craft application we are seeing many of the high horsepower to weight engines needing rebuild at 2,000 hours or thereabouts."

In either lifetime my guess would be about the same amount of fuel was consumed by the speed boat app and the noisemaker app.

A large noisemaker will frequently not even shut down for an oil change , a valve is thrown and a few hundred gal of pre heated oil now lube the unit.

 

[RickB]

In either lifetime my guess would be about the same amount of fuel was consumed by the speed boat app and the noisemaker app.

FF makes a very good point regarding generators.

Again, owner expectations and lack of understanding of ratings has a lot to do with many of the myths that thrive on internet boating sites.

Take a look at Deere's definition of ratings. Take note of the difference between recreational marine propulsion and marine generator prime mover. The bold typface and color for emphasis is mine.

"M5: The M5 rating is for marine recreational propulsion
applications that operate 300 hours or less per year and
have load factors* below 35 percent. This rating is for
applications that use full power for no more than 30
minutes out of each eight hours and cruising† speed the
remainder of the eight hours, and do not operate for the
remaining 16 hours of the day.
Possible applications: Recreational boats in the U.S.,
tactical military vessels, and rescue boats outside the U.S.

Marine generator: The marine generator engine rating
is the power available under normal varying electrical
load factors* for an unlimited number of hours per year
in commercial applications. This rating incorporates a 10
percent overload capability, and conforms to ISO 8528
prime power. Average load over a 24-hour period shall not
exceed 67 percent of the prime rating, of which no more
than two hours are between 100 percent and 110 percent
of the prime rating.
The marine generator rating is restricted to generator
applications only. The criteria used to establish marine
generator application ratings are the same used to establish
industrial prime power generator application ratings."

Those who believe generator engines are somehow rated and operated at lower load factors are very much living in diesel fantasyland. Take the JD 4045 (it is a very common generator drive engine on medium sized yachts) for example ... it is rated to deliver up to 166hp@1800 rpm in marine generator use. That engine displaces 275 cubic inches which, if we subscribed to the half hp to cubic inch myth would be limited to less than 140hp and you can forget about any overload.

The 4045AFM85_D_M4_AP version of the 4045 is rated for 225hp@2600rpm ... do your own calculations on that one.

When we work with a new generator installation we run them on a load bank for 100 hours at varying loads including 10 percent overload while monitoring all parameters. My own system monitors and records power and exhaust parameters and I can attest that those generators live a much harder life than all but a very few propulsion engines that use the same moving parts.

 

[Art]

IMHO - All the do this or do that stuff is pretty much a bunch of hooey!


If a "well designed" engine is used for nearly any purpose and is not often pushed past 3/4 total output (generally keeping it at 2/3 output is best), with excellent maintenance always applied, there is good chance the owner will get maximum service life from that engine.


Responsibly used and looked after engines last longer - it's just that simple.


If anyone wants to play high-output games with their engine(s)... then be ready to pay the consequences$$$!

 

[Ski in NC]

While the Deere genset engine is rated for 160hp, in an actual yacht duty cycle the are often running long periods of time below 50%. They are sized for worst case situations like running multiple chillers and starting large chiller compressors, but in actual duty they are running mostly well below full load.

 

[RickB]

While the Deere genset engine is rated for 160hp, in an actual yacht duty cycle the are often running long periods of time below 50% ... in actual duty they are running mostly well below full load.

Oh My Gawd! Do you mean they are running at less than 1/2hp per cubic inch displacement?! The local myth is that power level is what makes a diesel "happy" and assures long life.

In reality those low power factors are what kills generator engines. It is what provides me with a very good business. The SeaClean system (pardon the commercial aspect of the reference) incorporates a load bank function that helps to maintain a higher power factor to reduce or eliminate "underloading."

Most of the content in the past few posts just confirms what I wrote earlier:

"It might have more to do with owner expectations. When you buy an engine you are buying power - horsepower hours to be exact.

Think of the engine as if it is a fuel tank. If you want to extract a large amount of power in a relatively short period you will empty that tank earlier."

Don't blame the engine for not supplying more than what the manufacturer stated very clearly it will supply. The biggest failure lies in your own expectations and misconceptions, not the machinery.

As long as you operate the engine within its rating parameters (and comply with the published maintenance schedule) you will get what you paid for.

Read all the posts about engines, you will soon see that most of the failures and problems have nothing to do with engine design or ratings but arise from operator ignorance, poor maintenance, and owner created problems rooted in homemade auxiliary systems or just plain old fashioned ignoring the machinery until it breaks.

 

[RickB]

They are sized for worst case situations like running multiple chillers and starting large chiller compressors...

That is very "old school." I can't remember last time I was on a yacht that did not use VFD control of chillers or at least a soft start system for large inductive loads. The days of sizing for massive starting loads through an "across the line" starter are for the most part, long gone.

Load control, load sharing, and shedding has become very sophisticated on modern yachts. And before anyone starts off on the "megayachts don't apply to our boats" soapbox again, we are talking about the engines used to drive the generators, the same engines that your own boat uses to turn the screw so save your fingertips and find another windmill to tilt at.

 

[Ski in NC]

Ha! Yep, everything I deal with turns out to be old skool!!! Sounds like the new tech has the loading thing sorted out, both on the low and high side. The larger yachts I've worked on still had 20 or 30yr old machinery.
And there, under loading was a big deal.

 

[RickB]

Sounds like the new tech has the loading thing sorted out, both on the low and high side.

I hope not ... Power management is getting pretty darn good but if they ever sort out the loading thing I might lose a lot of business!

One of the issues we run into is the boats that used to use halogen lights for nearly everything (and consumed power to chase the dark away and even more power to get rid of the heat the things produced) have replaced them with LED fixtures and the overall electrical load has dropped so now the gens may be oversized.

The opposite of that is some boats keep adding loads so the gens are undersized now and need hi tech load management to keep things working. But the problem with that is with 2 or 3 gens of the same size, when the second or third comes online automatically the load on each might drop too low ... it is a real juggling game.

I am philosophically opposed to loadbanks but have come to the conclusion that they do have a place on some boats so have developed an exhaust cooled loadbank that eliminates all the pumps and plumbing that make the existing designs so problematic.

 

[bayview]

The quoted ratings from Deere above mention a load factor of 35%. Nobody responded to that and few owners probably understand what that means but it is very far from what the salesmen tell you that diesels need to be run hard.

The commercial rated engines may have a load factor near 100% but they are running at low power per liter.

IMO run any decent diesel at 30HP per liter and they will last forever. Up that to 60 and watch parts fly off.

 

[Twilight time]

Hey Salty , Just around the corner from you im Portsmouth have a SENATOR 35 with a Perkind 6-354 its almost bullet proof figure to get around 3 gph at 2100rpm make 6.8/7 knots

 

[RT Firefly]

 

[Ski in NC]

I am philosophically opposed to loadbanks but have come to the conclusion that they do have a place on some boats so have developed an exhaust cooled loadbank that eliminates all the pumps and plumbing that make the existing designs so problematic.

I too don't like wasting fuel just to keep load up, but that is better than the alternative.

In my experience, gennie engines can tolerate running light load... but not continuously. The question then becomes how light a load is ok, and for how long.

I have seen several examples where the gen runs light load all night, maybe only 15% load, then loads up over 50% for at least an hour in the morning with cooking and water heaters. Then high load during the day with AC fighting solar. This example, gen well over 10k hours and no symptoms. So 10hrs of light load seems ok.

Then another one in sportfish, oversized, runs light load while fishing, then back on shore power, never really loaded, and liners glaze and it is using oil before 2k hrs.

Then another in similar sportfish, gen loaded to 80% for several hours at new install to break in. Then goes into a light load duty cycle and never has a problem for several k hrs. So break in seems very important.

Another propulsion engine did several thousand miles at 1000rpm and started using oil. Diagnosis: too light a load and glazed liners. Prior to overhaul, recommended run it hard on a few trips and track oil use. That one quit using oil almost completely!! Even when going back to slow cruise, oil use normal. Although he does once a day at least load it up for an hour. Overhaul canceled.

Many sportfish drag baits all day long at dead low idle. But power up for getting out and back in. Most have no problems with glazing/oil use/blowby.

Loopers in the canals stuck idling for many days, yet seem ok once out.

Many more examples seem similar to the above.

It seems that low load is only evil if near continous. Getting load up once a day seems ok.

A good hard break in seems important.

But I have trouble lumping all this together and coming up with a good "minimum" load pattern to recommend for both gens and mains.

And I imagine each engine is different in how sensitive they are to low load ops.

Complicated.