Starting Engines

SomeTexan said:

If it weren't for bad heat exchangers, what problems are there?

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Overloading(overpropped)!!! Probably the biggest killer. Again, they are more susceptible because they are so heavily loaded. Heat is the killer of longevity of ANY engine. The more highly loaded they are, the more heat is generated.

Baker said:

Todo bien mi amigo!!!! No worries. And I apologize for getting all pissy!!!... I just keep getting frustrated with these things and talking to mechanics that talk about broken tips from injectors like it is a normal every day thing. Like "weak" cylinders are a normal every day thing....etc...

I bought this boat REALLY hoping I was wrong....and I still hope I am.

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The only weak injector tips I have encountered are the newer common rail engines, 6btb. I've had issues getting a whole set of new injectors to work. But that's not a cummins part. The 6.7's have weak cylinder walls, trying to keep as much as they could and make them bigger for the road diesel rule changes. That's a nightmare. But the old 5.9 is a tough longblock. Maybe an aftermarket company would do a better job setting them up for marine use. If coolers are failing that often, there is a problem. Personally I'm a slow boat guy, I would run a keelcooler and keep the saltwater out of my boat. As much as possible anyways. I really don't think a fuel cooler would do much, and would bypass them for trial, but aftercoolers can be upgraded.

Baker said:

I bought this boat REALLY hoping I was wrong....and I still hope I am.

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John: That's quite a "telling statement." You bought the boat "hoping you were wrong." In other words, you knew of these Cummins problems before you bought the boat! Why on earth did you buy it then? Low hours? Price? Was it local? Lots of room?
Why? There were things that drew you to the boat that were not Cummins related, yet you bought the boat & now your are pissed at Cummins!
Think about it...

Baker said:

Overloading(overpropped)!!! Probably the biggest killer. Again, they are more susceptible because they are so heavily loaded. Heat is the killer of longevity of ANY engine. The more highly loaded they are, the more heat is generated.

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Crap factory turbo's. The exhaust housings are too large. It's been the cummins #1 problem since day one. If they had a 12cm exhaust housing, they would spool and run better down low. They work ok at max rpm, but now so good below that. But yea, over propping anything is bad.

SomeTexan said:

If it weren't for bad heat exchangers, what problems are there?

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Problems with any modern marine diesel:

1. Inattentive owners
2. Bad boat building practices especially regarding exhaust side
3. Wrong props
4. Not following required maintenance procedures
5. Operating your vessel at more than 0.5 HP drawn per cubic inch displacement if propped wrong.
6. Inattentive stingy and cheap owners

Did I say inattentive owners? Did I mention props? Few pickups, irrigation motors or gensets suffer the indignities a marine engine is subjected to due to inattentive owners.

It is a real crap shoot on the used boat market, well beyond the color of paint on the engine due to inattentive owners who think a marine engine is like their pickup, SomeTexan excepted of course.

sunchaser said:

Problems with any modern marine diesel:

1. Inattentive owners
2. Bad boat building practices especially regarding exhaust side
3. Wrong props
4. Not following required maintenance procedures
5. Operating your vessel at more than 0.5 HP drawn per cubic inch displacement if propped wrong.
6. Inattentive stingy and cheap owners

Did I say inattentive owners? Did I mention props? Few pickups, irrigation motors or gensets suffer the indignities a marine engine is subjected to due to inattentive owners.

It is a real crap shoot on the used boat market, well beyond the color of paint on the engine due to inattentive owners who think a marine engine is like their pickup, SomeTexan excepted of course.

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That may be a stretch...especially those items in small business commercial service.....

Which boils back down to what is becoming more popular around here...take basic care of a diesel and it will last...screw TOO bad with it or run it for awhile with no coolant and all bets are off....

sunchaser said:

Problems with any modern marine diesel:

1. Inattentive owners
2. Bad boat building practices especially regarding exhaust side
3. Wrong props
4. Not following required maintenance procedures
5. Operating your vessel at more than 0.5 HP drawn per cubic inch displacement if propped wrong.
6. Inattentive stingy and cheap owners

Did I say inattentive owners? Did I mention props? Few pickups, irrigation motors or gensets suffer the indignities a marine engine is subjected to due to inattentive owners.

It is a real crap shoot on the used boat market, well beyond the color of paint on the engine due to inattentive owners who think a marine engine is like their pickup, SomeTexan excepted of course.

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So, a whole bunch of problems that have nothing to do with cummins? Even in trucks, stupid people can kill them. I properly maintain my trucks, and I understand there is more to maintain in a boat. If installed correctly and maintained by a competent owner/mechanic, what problems occur? Owner neglect doesn't count.

sunchaser said:

Few pickups, irrigation motors or gensets suffer the indignities a marine engine is subjected to due to inattentive owners.

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This is by far the most idiotic statement I have read on this site. Bar none.

I know farmers who run these things for 2 months straight, then park them in a field for 10 months. They charge the battery, change the oil, and slap them right back into service. 90% of truck owners never tow enough of a load to break them in properly. Ive met people that dont think you have to change fuel filters until the engine wont run. Equipment being operated by minimum wage employees, think that doesn't get abused? I don't know what kind of fairy tale world you live in, but reality it is not.

SomeTexan said:

This is by far the most idiotic statement I have read on this site. Bar none. I don't know what kind of fairy tale world you live in, but reality it is not.

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A stroll through a large working boat yard may change your mind, And then again --------------

sunchaser said:

A stroll through a large working boat yard may change your mind, And then again --------------

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My family are farmers, and their friends are farmers. Some ranching too. How many boats are run for a couple of months, nonstop, then shut down until next year? No winterizing, nothing. Most of the time, if the oil was more than just topped off, it was because I changed it. Filters, just blow them out and put em back in. Heavy equipment, if it ain't broken, then it's out making money, who cares if it needs an oil change, it's leaking, whatever. And it's being run by someone making minimum wage who wants it to break. He gets paid to stand around same as if he is working, so screw it. Something like a boat, that is owned by someone who's life may depend on it, should really take more pride in it. I don't doubt you if you are talking about commercial fishing vessels that are corporately owned. Corporation= we want money coming in, but not going out. But I thought we were talking about pleasure boats. When you spend big money for something you are proud to call your own, don't you take care of it? I guess there are stupid people everywhere.

The point was, it's not major engine failure that kills these cummins, it's an accessory on the engine that fails. That's a bad job making it marine ready, not the engine. The models without aftercoolers and fuel coolers don't seem to have problems. Right?

SomeTexan said:

This is by far the most idiotic statement I have read on this site. Bar none.

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Please have more respect for other community members. You can make your case without being insulting.

Thanks,
Mod Team

Tom

Don't fret on my account, I love Texans. Especially those who seem passionate. Now we can wait and see what kind of boat issues SomeTexan brings forth.

By the way SomeTexan, my non boating diesel has been fun and illustrative too. I have come to find that most on this Forum bring a lot of good knowledge to the boating issues table.

Being provocative is fine, as Tom B says, remember the lines. This isn't twitter. Many of us know each other and have estblished some good friendships.

SeaHorse II said:

John: That's quite a "telling statement." You bought the boat "hoping you were wrong." In other words, you knew of these Cummins problems before you bought the boat! Why on earth did you buy it then? Low hours? Price? Was it local? Lots of room? Why? There were things that drew you to the boat that were not Cummins related, yet you bought the boat & now your are pissed at Cummins! Think about it...

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I'm not pissed at Cummins. Just frustrated. And yes I bought the boat for all of the non cummins related reasons stated above. And I do get a little irritated when people tell me they are the greatest engines on earth when it seems they fail more often than other makes.

Allow me to sum it up in my opinion. Cummins marine diesels appear to be less tolerant of owner neglect than other models. How's that. Pleasure boat diesels are the most neglected of all Diesel engines. So yes, if you bought a boat from brand new and you have maintained it well they should give you good service. I don't have the means to buy a brand new diesel motor yacht so I am stuck with dealing with the neglect of others. And the good ole saying of feed it clean fuel and clean oil and it will run forever does NOT apply to these engines. You need to do a helluva lot more than that.

And some Texan, there is a company in California that has re engineered most of the peripherals on this engine.

I apologize to everyone for getting so far off on this tangent...especially when there are passions and emotions involved. We like to think we made the right decisions when we spend a lot of money on something. You just have to be very hands on with these things.

I don't see the point of bashing an engine because of problematic heat exchangers. The lower output models without them don't have those problems. The idea of a fuel cooler seems insane, unless the engine room gets hot enough to get the fuel to vaporize. Other than that, just being pressurized in the pump builds quite a bit of heat. If the aftercooler is a known problem, that's the problem, not the engine. Once one of these has failed and exposed an engine to seawater, consider it a loss until its been torn into. I'm talking pulling the head minimum. That would be on any diesel engine. But I am, and have always been a mechanic. I won't run something until I have pinpointed and fixed the problem.

In Baker's case, I believe he said he was having problems with the engine that did not have the fuel cooler failure. Ring sealing issue. It was a low hour used boat. Did the original owner just idle it around and glaze the cylinders? Just like any diesel, they don't like abuse like that. Personally, I would at least pull injectors and scope the cylinders. Stuff like fuel wash, glazed cylinders, broken rings, and the big one, contamination, are all easy to spot. Did the previous owner idle out of harbor on one engine, start the second one and slap full throttle? That can break a ring. It's used, you don't know what torture it's been through. Blaming an engine for a previous owners abuse and/or neglect is unfair. Need help with it, pm me. I'm more than willing to take a look at info you have, and offer opinions. If you were closer, I would offer to head over and take a look. I can and have built these engines from bare blocks. I will help in any way needed. Heck, I can build them, blueprint and balance them into the smoothest running pair of cummins you have ever heard. Help I offer freely, but tolerance to insulting an engine you don't know it's background, no.

SomeTexan said:

The idea of a fuel cooler seems insane, unless the engine room gets hot enough to get the fuel to vaporize. Other than that, just being pressurized in the pump builds quite a bit of heat.

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The injection pump adds a tiny amount of heat to the fuel only because the pump housing is warm because it is mounted on the engine. If pressurizing fuel added heat it would be impossible to have a high pressure common rail system. If a good old fashioned mechanical injection pump heated fuel by squeezing it to 3,000 psi, just imagine what the temperature would be at 30,000.

The normal limit for fuel entering the injector pump is around 140. That limit exists to avoid cavitation and ensure lubrication of the plungers.

The fuel cooler is on the return side, not the supply. It is intended to cool hot return fuel so the tank is not heated which causes increased microbial growth and hastens the production of asphaltenes and other oxidation products. If you have big tanks or the return doesn't go to a very small day tank that is also the fuel supply tank then a fuel cooler is hardly required.

It is also worth noting that in the commercial world, it is not acceptable to have fuel at or above its flash point in a fuel tank or any place other than on the engine itself. The flash point of marine diesel is 60C or 140F ... does that number sound familiar?

Fuel coolers are hardly "insane." They have a place in many installations but perhaps recreational trawlers operating at low power while returning fuel to relatively large tanks are not one of them.

With regard to tearing an engine down because it got wet, electronics and accessories aside, it is normal practice to keep the engine submerged (even in seawater) until it can be immediately washed in freshwater, and the oil and fuel system flushed. Quite often that is all it takes to restore the engine to normal operation. It is not instant death by any means.

RickB,

1, you would be surprised how much heat is added by the injection pump. Compressing anything creates heat. When you are talking over 1000psi, doubling temp isn't uncommon. But, it's under pressure, it won't vaporize.

2, makes sense, but that is entering the pump, as you said. Heading to the injector it's considerably hotter.

3, I did not know the cooler was return side. I guess it would make sense in a commercial application where aside from just a pair of engines running, you have a generator or 2 and a hydrolic pump all running, heating an engine room. More heated return fuel too. It still sounds overkill in the small boat we are talking about.

4, I wholeheartedly disagree. That is the trashy way to do it. If an engine is worth saving, it's worth doing it RIGHT. Wash it out with freshwater and all you have done is fill oil passages with something that isn't oil. The only proper way to fix that ghetto cleaning job is to tear down, inspect and replace as required, and properly lube the engine. As an engine builder, I refuse to do crap work. When I work on something, I make sure it's done right, or not at all. Flushing with water does not remove all contaminates, not by a long shot. It is more likely to introduce contaminates than remove them. A little salt by the rings and your bore won't last, it's abrasive and corrosive, a bad combo. Any engine treated like that is a ticking time bomb. Not until every part has been tanked/vatted and/or otherwise properly cleaned is it ready to run. While you are in there, why not rings and bearings? Not much extra money for peace of mind. It will cost a lot more when the engines are back in the boat than if they are already apart.

If marine tech's really consider that the proper way to handle a seawater contaminated engine, I would recomend paying diesel equipment tech's, or guys like Hamilton performance to take a look. I know the guys at Hamilton, they would become violent with anyone suggesting flushing an engine with water in that situation. Why? Because that is just short of raping the customer.

UUUGGGGGHHHHHH!!!!!! ST...did you not click on my link???????? I am not bashing engines based solely on what I have in my bilge!!!! I am not bashing engines based on "heat exchangers" failing!!! I AM BASHING THE ENGINE BASED ON REALITY!!! NOT THEORY!!!! Theoretically, these are great engines. The reality is, they do not do that well in a marine application. On that link I posted, there are 918 hits....all with twin Cummins engines. Within the first 7 clicks, I found 2 boats that had rebuilt engines in them while their stablemate had less than 2000 hours. That is a very random, albeit unscientific, sample. I SHOP BOATS!!! I find this to be quite common. THAT IS WHAT I AM BASING MY OPINION ON!!!!!!! REALITY....CAPICHE????!!!!

I will sum up my opinion one more time. The Cummins 6BT is a great engine. The Cummins 6BT SEEMS to be less tolerant of owner neglect(compared to other engines). Pleasure boat people neglect their engines. Therefore, Cummins engines don't do well in a pleasure boat application! If Tony Athens were here, he would say it is Cummins fault because "the book they wrote on how to maintain these engines it totally wrong." So a finger could be pointed at Cummins for improper maintenance instructions.

Now, more reality. Boats sink. Boats are salvaged. Part of that salvage is their engines. Rick's method of bringing them back to life is very COMMON and very REAL!!! And check this **** out.....VERY EFFECTIVE!!!! Engines done this way go on to live MANY MANY 1000s of hours.....REALITY!!!! It's where I live!

SomeTexan said:

1, ... When you are talking over 1000psi, doubling temp isn't uncommon.

2, ... Heading to the injector it's considerably hotter.

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That's a good pair ... care to document those claims?

Let me get this straight ... if I supply the pump with 100F fuel it will double the temperature when it reaches 1000psi? Is that what you are saying? What temperature does the fuel reach when it reaches the typical pressure at which a typical mechanical injection pump operates? Do you know what pressure that is? It should be pretty easy for you to document that temperature rise as well. How about getting back to us with that would you, please?

3, I did not know the cooler was return side. I guess it would make sense in a commercial application where aside from just a pair of engines running, you have a generator or 2 and a hydrolic pump all running, heating an engine room. More heated return fuel too. It still sounds overkill in the small boat we are talking about.

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You'll have to explain to me why that engine room is hotter than the little recrational boats that don't have substantial supply and exhaust fans and one heck of a lot less volume. have you ever been in a working engine room?

4, ...I know the guys at Hamilton, they would become violent with anyone suggesting flushing an engine with water in that situation. Why? Because that is just short of raping the customer.

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Sounds like a bunch of strange people who don't have much experience in real life marine operations.

And a quick clarification. I am likely quite alone on my disdain for these engines. There is a lot of "smoke" blown around about them. My ass just isn't that keen on inhaling it.

And one more thing...it is just FYI. According to Mr. Athens, the 6BT pumps 4 times more fuel than it uses. My tanks are relatively small(100 gals). At cruise each engine is burning about 8-10gph. If the temp doubles at each go round, I would explode in just a few hours.

Baker said:

If the temp doubles at each go round, I would explode in just a few hours.

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That must have been what happened to these guys ... they ran their engines for too long on a hot day!

Greetings,
Yup, hot fuel 'll do it to ya...

RickB said:

That's a good pair ... care to document those claims?

Let me get this straight ... if I supply the pump with 100F fuel it will double the temperature when it reaches 1000psi? Is that what you are saying? What temperature does the fuel reach when it reaches the typical pressure at which a typical mechanical injection pump operates? Do you know what pressure that is? It should be pretty easy for you to document that temperature rise as well. How about getting back to us with that would you, please?



You'll have to explain to me why that engine room is hotter than the little recrational boats that don't have substantial supply and exhaust fans and one heck of a lot less volume. have you ever been in a working engine room?



Sounds like a bunch of strange people who don't have much experience in real life marine operations.

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Yes, that is correct. Building pressure builds heat. This is a proven fact. Hydrolics built heat when used, turbo's built heat building boost. Put a heat gun on the injector lines, they will be considerably hotter than the pre-lift pump fuel line. It's the whole principal behind the compression ignition or diesel engine.

Pop pressure is different in different engines. I've seen from 600psi to over 30,000 psi. Depends on the system used.

Well, the retired shrimp boat I had looked at had 2 drive engines, 2 large gensets, 2 large hydro pumps all running, plus a back up genset and hydro. Big engine room, but stuffed full of running heat factories. Now, you are correct when you mention "little" engine rooms. I did not think of something small, smaller than walk in with standing head room doesn't interest me, so I wrote that off. Still shouldn't be bad if there is proper airflow. If not, it's a bad designed boat.


They are recognized as the best cummins engine rebuilders in the country. They worked with cummins to fix flaws with the common rail's before they were on the market. But, unlike the average sub par tech, they won't turn out an engine that isn't right. You should see the clean rooms where they build engines. Perfectionism at its best. Not some dirty shop, filling new engines with crud. People may "wash out" an engine, but that is the wrong way to do it. That is the mark of a sub standard mechanic. Think of it as, just because your friends are jumping off a cliff, should you do it too? The wrong way may work sometimes, but that still doesn't make it right. Of course, if all pleasure boat owners are as willing as you to do things the wrong way just to save a buck, I will believe boats are horribly owner abused. I would have thought that a major investment like a boat would draw people who considered it an investment and maintain it properly. I'm glad I am looking for an old hull and intend to rebuild everything myself. Properly.

Baker said:

And a quick clarification. I am likely quite alone on my disdain for these engines. There is a lot of "smoke" blown around about them. My ass just isn't that keen on inhaling it.

And one more thing...it is just FYI. According to Mr. Athens, the 6BT pumps 4 times more fuel than it uses. My tanks are relatively small(100 gals). At cruise each engine is burning about 8-10gph. If the temp doubles at each go round, I would explode in just a few hours.

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You would be surprised how much temp goes away when pressure drops. Fuel lines take heat out. A relatively small amount of heated fuel goes back. Most of the return fuel never sees full pressure and heat. It is excess to make sure the pump is properly supplied and doesn't cavitate.

Geez, I wonder why waterjet cutting machines don't produce great clouds of steam, or melt the crap out of fabrics, paper, or foam? Some of those buggers squeeze water up to around 100,000psi. Must be some kind of voodoo thing, do you think?

Hydraulic systems get hot because flowing oil through an orifice will increase the heat. It is a liquid with long molecules that release a lof of energy when they get disturbed, it's not a gas that expands by absorbing heat from outside or converting the work of compression into pressure and heat. If you have a 100 hp worth of hydraulic flow but only extract 50hp worth of work out of it, that other 50hp is going to be dissipated as heat.

Check out the temperature difference across a hydraulic reducing valve sometime ... the pressure drops drastically but it doesn't cool the fluid - quite the opposite, it gets hotter than a trawler forum argument with a pretender. Dropping pressure in a hydraulic system without doing work will produce heat. The pump only adds a tiny amount of heat from internal friction. The fluid does not compress enough to produce heat adiabatically.

Compressing a gas is a whole 'nuther process altogether and that is how a diesel engine works and why air gets hot when compressed by a turbocharger. Like many others with a little bit of the vocabulary, you need to attach the correct concept to the words if you want to make sense or try to explain how or why stuff works.

You've got quite a handly little IR thermometer if it can read an injector tube by itself. Tell you what I'll do, sometime in the next week or so I'll take an IR movie of fuel moving through a diesel injection pump so we can see how much it heats up.

SomeTexan said:

Most of the return fuel never sees full pressure and heat. It is excess to make sure the pump is properly supplied and doesn't cavitate.

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Would you be so kind as to supply a fuel system diagram for a Cummins engine that shows where the return fuel originates?

Most importantly by bringing the engine(s) to operating temp burns off any condensation inside the engine.

Some of you guys are talking past each other.

Compressing diesel does increase its temperature significantly But temperature is not straight away heat. Heat has another dimension per pound or per gallon or per something. So if you have high temperature and low volume or mass then you don't have so much heat. Conversly with reletively low temperature and a large volume you can have a lot of heat to deal with. Another point is that the hotter something is the faster it will give up its heat to something else. Enough of the thermodynamics. It is important to note that the return fuel on a diesel engine is hot from both compression and where its been and it has provided some lubrication to system.

O.B. Thomas, P.E.

obthomas said:

Some of you guys are talking past each other.

Compressing diesel does increase its temperature significantly But temperature is not straight away heat. Heat has another dimension per pound or per gallon or per something. So if you have high temperature and low volume or mass then you don't have so much heat. Conversly with reletively low temperature and a large volume you can have a lot of heat to deal with. Another point is that the hotter something is the faster it will give up its heat to something else. Enough of the thermodynamics. It is important to note that the return fuel on a diesel engine is hot from both compression and where its been and it has provided some lubrication to system.

O.B. Thomas, P.E.

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Now you really are talking past the subject. We are not talking about the number of BTU's transferred to the fuel in the injector pump plunger, the Texan stated that the temperature - the sensible temperature - of diesel fuel was doubled when pressurized to 1,000 psi and the temperature of the fuel lines was measured at twice that of the incoming fuel, that temperature rise being the result of compressing the liquid and producing a temperature high enough to raise the temperature of the fuel lines.

Not quite enough thermo in my opinion. The return fuel is hot because it is used to extract heat from friction within the injection pump and from the injectors within which it circulates. If you can show the math or by empirical evidence that liquid fuel is heated "significantly" by compression in the injection pump I will eat that crow but I am not going to worry too much about how much bird sauce I need to stock up on.

I believe that if you research it a bit further, increasing the pressure of diesel fuel at a couple of psig to 30,000psig at 40C will raise the temperature to about 45C ... with a specific heat of about half that of water I seriously doubt that the miniscule flow of fuel is going to rise the temperature of the lines to 80C by adiabatic compression. Increasing the pressure rapidly to 1,000 psig doesn't even register on any scale.

Like I offered, give me a bit of time to set up and I will provide an IR movie to show what gets hot at what rate when a diesel engine is fired up from ambient. The injector lines are not even on the real world map.

RickB said:

Like I offered, give me a bit of time to set up and I will provide an IR movie to show what gets hot at what rate when a diesel engine is fired up from ambient. The injector lines are not even on the real world map.

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Now THAT I would like to see!!!

Gentlemen,

While I find your intercourse somewhat entertaining (I keep waiting for the knock-out punch), I am finding it difficult identifying the relevance to my initial inquiry.

As I’m reading the posts I'm trying to determine what is fact, and what is opinion, (except Rick B, he tells you when it’s his opinion) or just plain fiction. It’s seems everyone speaks from a position of knowledge and yet there are some very opposing statements.
For my part, I have to sift through all the banter and try to extract something useful, but man, you guys don’t make it easy.

I don’t own Cummins engines. I saw a couple of brand new ones on pallets in a boat yard and they sure looked pretty slick. Apparently some guy was pulling his Hino’s out and putting those in.

It’s ok with me if you guys want to continue this UFC thing; I just thought I’d mention that you’re going down a different waterway.

I would love to see the movie too. Do we have to wear those funny glasses to watch it? KJ