skipperdude
Guru
Thanks RT. Gave me a good chuckle.
SD
SD
Good Engine, Bad Engine
- Thread starter divebums
- Start date
The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
Codger2
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I tend to lean in this direction. Although, as stated before, I love Cummins. If I were a long distance cruiser, however, and spending months at a time aboard, Lugger would be in my ER.
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ancora
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My advice is to check for parts availibilty for any engine you are looking at. Some manufacturers do not support their older products, Volvo in particular.
Nomad Willy
Guru
How many engines are w/o a marinization. Engines where they make their own everything. Many are in-between w their own line of engines and then to compete better in the marketplace in a certian HP range or spot they buy base engines from Toyota, Mitsubishi, Kabota, John Deere and many others. I think Yanmar and Volvo qualify in this way. Does Cummins Make all their own stuff? Probably not.
I was very drawn to a 47hp engine (Mitsu) (rated w a fan) tractor/industrial engine that was rated at 2500rpm. At first glance it seemed the best engine ever but it was too much power and it had a quite to very low mounted starter. The excessive power and the starter location moved me to choose a smaller engine rated at 3000rpm and a high mounted starter.
Of course issues like that starter aren't black and white. They come in degrees. How many "marine" engines have elements or lots of elements like the starter motor example I give above? NONE of our modern engines, that is the basic engine as designed .. is a marine engine. They are ALL designed and built for some other purpose and then converted to "marine" engines. I'm sure there is something lost in the "conversion" process. For example most all marine engines of the 50s had their flywheel mounted on the front of the engine. The engine could then be mounted as low as possible in the hull for best shaft angle and best CG.
What other things are lost in the conversion of truck to boat engine that is not obvious to most people (like us). There may be 30 or 40 things, mostly small that effect the performance of the engines in a boat. The location of the seawater pump on one of the old Perkins engines may be an example of this. The oil filter on my engine was not in a user friendly place (it would have been if the engine was on a tractor) and all these little things added up could make a fairly good marine engine that had a much better than fair basic block. Perhaps there was more to it like cooling or safety?
Obviously the ideal engine would be one that had an extremely long lasting and high performing BB (basic block) with it's details leaning toward the marine version in desirability. Then the ideal engine marinizer would cut a minimum of corners and minimize building to a price to build the best engine for a boat possible and still be price competitive. Utopia? Perhaps .... but they did it in the 50s.
So what say you gear heads? What are the features of a marine engine make it the best. What marine engines are the best and what makes them that way.
I was very drawn to a 47hp engine (Mitsu) (rated w a fan) tractor/industrial engine that was rated at 2500rpm. At first glance it seemed the best engine ever but it was too much power and it had a quite to very low mounted starter. The excessive power and the starter location moved me to choose a smaller engine rated at 3000rpm and a high mounted starter.
Of course issues like that starter aren't black and white. They come in degrees. How many "marine" engines have elements or lots of elements like the starter motor example I give above? NONE of our modern engines, that is the basic engine as designed .. is a marine engine. They are ALL designed and built for some other purpose and then converted to "marine" engines. I'm sure there is something lost in the "conversion" process. For example most all marine engines of the 50s had their flywheel mounted on the front of the engine. The engine could then be mounted as low as possible in the hull for best shaft angle and best CG.
What other things are lost in the conversion of truck to boat engine that is not obvious to most people (like us). There may be 30 or 40 things, mostly small that effect the performance of the engines in a boat. The location of the seawater pump on one of the old Perkins engines may be an example of this. The oil filter on my engine was not in a user friendly place (it would have been if the engine was on a tractor) and all these little things added up could make a fairly good marine engine that had a much better than fair basic block. Perhaps there was more to it like cooling or safety?
Obviously the ideal engine would be one that had an extremely long lasting and high performing BB (basic block) with it's details leaning toward the marine version in desirability. Then the ideal engine marinizer would cut a minimum of corners and minimize building to a price to build the best engine for a boat possible and still be price competitive. Utopia? Perhaps .... but they did it in the 50s.
So what say you gear heads? What are the features of a marine engine make it the best. What marine engines are the best and what makes them that way.
Max Simmons
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If I was looking at a boat in the 80's - 90's vintage, I'd make sure that it has Perkins or FL, just for parts availabiility and they seem easy to work on. The cooling system can be the most expensive part to replace. I didn't know at the time, but the Manicooler heat exchanger on my Perkins runs several thousand (like 6?) to replace. My engine surveyor didn't mention this to me at the time, and so far they have not given me any issues.
The transmissions should be reviewed with the same criteria.
The transmissions should be reviewed with the same criteria.
jleonard
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I have had boats with Perkins T6.354, Ford-Lehman 120, and Cummins 6BTA. I have also worked and helped owners work on many of each of those. I have also worked on several Cummins 6BT engines in trucks.
For me the best by far of that group is the Cummins 6B series. They are very simple to maintain, most things are accessible (except the RW pumps on some models), parts (oem and aftermarket) are available everywhere including NAPA, and there is a lot of model to model interchangability. Any diesel truck mechanic can work on them if required. The base engines are built in huge volumes and the marine "add ons" are pretty robust in most cases.
For me the best by far of that group is the Cummins 6B series. They are very simple to maintain, most things are accessible (except the RW pumps on some models), parts (oem and aftermarket) are available everywhere including NAPA, and there is a lot of model to model interchangability. Any diesel truck mechanic can work on them if required. The base engines are built in huge volumes and the marine "add ons" are pretty robust in most cases.
Phil Fill
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We don't have a lot of experience with marine diesel engines and we are wondering what experiences people have had with various engines. I'm sure marine engines, just like any other product we buy, have some that are held in high regard and some that are not. We're wondering what peoples experiences are regarding different makes and models of marine engines when it comes to reliability, maintainability, availability, affordability, etc. It would be great information to know as we shop around and see various boats with various engines. We look forward to your experiences and opinions.[/QUOTE]
Whatever engine you get, make sure parts and service in your area are readily available, especially in the cold northern climate where the boating season are short. If you can not get parts and service in your area it may not matter how reliable the engine is. I don’t recommend engines as they all need maintenance/service. How the engine was maintained and its present condition is important. Once you find THE BOAT let us know!
Whatever engine you get, make sure parts and service in your area are readily available, especially in the cold northern climate where the boating season are short. If you can not get parts and service in your area it may not matter how reliable the engine is. I don’t recommend engines as they all need maintenance/service. How the engine was maintained and its present condition is important. Once you find THE BOAT let us know!
Chuck Gould
Senior Member
If you are looking at previously owned boats, the brand name of the engine will often be less important than how well it has been maintained. On a much older boat, do ask around about parts availability. Some engines that were in common use a while back, (the Cummins "triple nickel" comes to mind as an example) might have been fabulous engines in their day, and maybe still are if well maintained, but eventually something will break and parts availability can be an issue.
I'm a huge fan of Perkins. Just personal preference and experience. There are many other good choices as well.
If hoping for a long lifespan from your engine(s), one of the old "isms" that seems to be consistently valid is the 2:1 ratio. See if you can find an engine that displaces two or more cubic inches for each HP developed. (Example would be a 354 cu in inline six producing 165 HP). Especially some of the newer engines rely on running much higher RPM to achieve rated HP. Most of those legendary 15, 20, 25,000 engines are slower turning.
I'm a huge fan of Perkins. Just personal preference and experience. There are many other good choices as well.
If hoping for a long lifespan from your engine(s), one of the old "isms" that seems to be consistently valid is the 2:1 ratio. See if you can find an engine that displaces two or more cubic inches for each HP developed. (Example would be a 354 cu in inline six producing 165 HP). Especially some of the newer engines rely on running much higher RPM to achieve rated HP. Most of those legendary 15, 20, 25,000 engines are slower turning.
JD
Guru
Greetings,
Mr. SD. Cat man huh? Good thing your not this.....then again....
If SD looked like that he/she would get my vote for Hall of Farmer.
RT Firefly
Enigma
Greetings,
Hall of Farmer? You KNOW farmers that look like that?
Hall of Farmer? You KNOW farmers that look like that?
bfloyd4445
Guru
nice to have reserve power but i believe engines are designed to be most efficient at rated hp and load. When operated way way below the design rpm there is a loss in efficiency and more combustion byproducts form to dirty the oil, engine, and air. So i guess its kinda a trade off. Maybe not because modern computer controlled engine systems can tweak the air fuel ratio to maximize efficiency.
So should we all go out and re power with new computerized efficient engines?.....
anyone know the answer?
bfloyd4445
Guru
Not sure the 2:1 thing is valid with todays modern engines based upon what i see in the auto industry in which its closer to 1:1 and they seem to live long trouble free lives. All turbo's and last hundreds of thousands of miles. Of course we wont know for years if this will hold true for the marine versions
RT Firefly
Enigma
Greetings,
Auto engines only WORK about 20% of the time. They're coasting or idling the rest. Marine engines are closer to 80%-90%. No coasting. I knew a fellow with two 6-71 TT's in a sport fish. Expected time before a re-build was about 5000 hrs. NA DD's last substantially longer than that. Anecdotal yes, but just sayin'
Auto engines only WORK about 20% of the time. They're coasting or idling the rest. Marine engines are closer to 80%-90%. No coasting. I knew a fellow with two 6-71 TT's in a sport fish. Expected time before a re-build was about 5000 hrs. NA DD's last substantially longer than that. Anecdotal yes, but just sayin'
OFB
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Good engine / Bad engine .
Well after thousands of hours using engines.
There are days that end with GOOD ENGINE , GOOD ENGINE!
Then there are days that just never seem to end BAD ENGINE BAD !
Most engines seem to need a thump from a very big hammer at some point in there life.
Some folk carry a big stick around. Yet for me that "pollish socket set" a very big hammer and some epoxy along with some life saving beer seems to get me home most of the time.
YMMV.
Well after thousands of hours using engines.
There are days that end with GOOD ENGINE , GOOD ENGINE!
Then there are days that just never seem to end BAD ENGINE BAD !
Most engines seem to need a thump from a very big hammer at some point in there life.
Some folk carry a big stick around. Yet for me that "pollish socket set" a very big hammer and some epoxy along with some life saving beer seems to get me home most of the time.
YMMV.
Chuck Gould
Senior Member
Can you think of any disadvantage in choosing a higher displacement to HP ratio, when available?
psneeld
Guru
psneeld
Guru
Are you willing to bash Chevrolet for no longer supporting the Corvair?
Sure....if there were as many Corvairs on the road as there are older Volvo's marine diesels still in use percentage wise....
That's why Furuno gets such high marks for supporting their marine electrionics for so long..usually WAY past the competition. And that's why the smaller vessel (read less big bucks) commercial crowd speaks so highly of them.
Chuck Gould
Senior Member
Sure...lighter, smaller, more efficient...need I go on????
I was referring to engine longevity, the advantage originally claimed for the old 2:1 standard. Even *if* some smoking hot little diesel revved up to 3500 or more is "lighter, smaller, more efficient"- is it likely to outlast, or last as long, as a larger heat sink running at 1800 to 2000?
From the longevity aspect, I fail to see any advantage to a high revving small engine over a slower revving larger engine rated at the same HP, and I see no disadvantage in choosing the larger engine.
It would be my opinion that engine weight in a true trawler application, running near hull speed, isn't as crucial as with a ski boat or a day cruiser.
For the OP---- One more thing to know about the Ford Lehman 120. Their raw water setup is part of the Lehman marinization package. It includes a Lehman-designed pump drive aka drive coupler that gets its power from the accessory case on the front of the engine. The drive powers an off-the-shelf Jabsco flexible impeller pump.
The Lehman drive coupler was designed by Bob Smith and he's the one who told me what I'm about to tell you (which was also seconded by our diesel shop).
The drive coupler is not a good design. It seemed to be a good design at the time but it proved to be very difficult to manufacture and is the only Lehman component to have ever had a factory recall (according to Bob).
But over time the drive proved to have a fatal flaw (which was not the cause of the recall) which is the drive tang on the pump end of the driveshaft. The fatal flaw is that eventually the tang, which is like a real fat screwdriver blade, fatigues, cracks, and breaks.
When it breaks--- and according to Bob all of them eventually will--- the raw water pump immediately stops and the flow of raw cooling water immediately ceases. At cruise power it takes only moments for the engine to overheat, and the number one killer of the FL120 is overheating (for several reasons).
The problem is that the Lehman drive coupler is no longer available new and hasn't been for a long, long time. While the tang can be repaired by welding, Bob told me that these repairs are very short-lived.
So there are only two solutions. One is get another drive coupler off an FL120 that is being parted out. Problem here, of course, is that the tang on the parted-out coupler may itself be close to failing.
So the real solution is to toss the whole thing, Lehman drive coupler and the Jabsco water pump, and replace them both with a brand new, one-piece Johnson pump that is a bolt-on replacement.
This is what we did on both our FL120s when the removal of one of the Jabsco pumps for overhaul revealed a failing tang on the drive coupler. So we had the couplers and pumps on both engine replaced with 1" Johnsons. The coupler on the other engine proved to be okay so we have kept it and the Jabsco attached to it as an emergency back up raw water pump system should we ever need it (not likely).
This is a very specific detail, I know, but should you end up looking at a boat with one or two FL120s, keep in mind this potential problem, which becomes more likely the more hours there are on the engine(s). If the engine(s) in a boat you're looking at has/have the Johnson conversion, that is a Wonderful Thing.
The Lehman drive coupler was designed by Bob Smith and he's the one who told me what I'm about to tell you (which was also seconded by our diesel shop).
The drive coupler is not a good design. It seemed to be a good design at the time but it proved to be very difficult to manufacture and is the only Lehman component to have ever had a factory recall (according to Bob).
But over time the drive proved to have a fatal flaw (which was not the cause of the recall) which is the drive tang on the pump end of the driveshaft. The fatal flaw is that eventually the tang, which is like a real fat screwdriver blade, fatigues, cracks, and breaks.
When it breaks--- and according to Bob all of them eventually will--- the raw water pump immediately stops and the flow of raw cooling water immediately ceases. At cruise power it takes only moments for the engine to overheat, and the number one killer of the FL120 is overheating (for several reasons).
The problem is that the Lehman drive coupler is no longer available new and hasn't been for a long, long time. While the tang can be repaired by welding, Bob told me that these repairs are very short-lived.
So there are only two solutions. One is get another drive coupler off an FL120 that is being parted out. Problem here, of course, is that the tang on the parted-out coupler may itself be close to failing.
So the real solution is to toss the whole thing, Lehman drive coupler and the Jabsco water pump, and replace them both with a brand new, one-piece Johnson pump that is a bolt-on replacement.
This is what we did on both our FL120s when the removal of one of the Jabsco pumps for overhaul revealed a failing tang on the drive coupler. So we had the couplers and pumps on both engine replaced with 1" Johnsons. The coupler on the other engine proved to be okay so we have kept it and the Jabsco attached to it as an emergency back up raw water pump system should we ever need it (not likely).
This is a very specific detail, I know, but should you end up looking at a boat with one or two FL120s, keep in mind this potential problem, which becomes more likely the more hours there are on the engine(s). If the engine(s) in a boat you're looking at has/have the Johnson conversion, that is a Wonderful Thing.
Nomad Willy
Guru
Chuck,
Nobody should care about how long an engine lasts or what rpm it is intended to run at. At least 99% of us will never wear out the engine w the shortest engine life expectancy. Lots of engines get killed but not worn out. So what does it matter how long some guru says it's supposed to last or what rpm it's run at. Makes no never mind.
Nobody should care about how long an engine lasts or what rpm it is intended to run at. At least 99% of us will never wear out the engine w the shortest engine life expectancy. Lots of engines get killed but not worn out. So what does it matter how long some guru says it's supposed to last or what rpm it's run at. Makes no never mind.
I have a 1991 Perkins TW6.354.4 it has 115bhp at 1500 rpm with max revs at 2850rpm.
Perkins 6.354 have been widely used in the marine and agriculture industries. They have turbo versions T6.354 and all sorts. Google and you'll get the info you require.
Cheers
Hendo.
bfloyd4445
Guru
thats funny but true. reminded me of one time i paid a guy almost $1000 to fix an engine and it still was the same as when he started. He said another $500 would fix it. I didnt have $500 but i had a six pack and bought a book, some wrenches were applied and with the help of the cardboard six pack which i used to make a gasket the engine was fixed and ran for years like that trouble free. Cost for the repair, one six pack and elbow grease. I wuz 21 at the time. Beer can be a live saver
psneeld
Guru
Chuck Gould
Senior Member
Certainly nobody is required to care. If the smaller high-rev diesels eventually develop a reputation as "2000 hour engines" or "2500 hour engines", and you put 150-200 hours per year on your engine for a decade before selling it it might have an impact on your resale value. Once again *if* the smaller high-rev diesels eventually develop a reputation....
We know what reputation the traditional, slower turning engines have developed and a 2000 hour diesel engine is no big deal, (pending oil analysis, etc). But try to sell a gas boat with 2,000 engine hours. A gas engine is going to be considered worn out at 2,000 hours by a lot more people than currently considering a diesel worn out with the same usage.
Until there is a widespread consensus about durability of the smaller engines, resale is a possible (not saying certain) concern.
Somewhere there are some pretty solid numbers about the relationship between the amount of fuel that has been pumped through a cylinder and its life expectancy without a rebuild. I'll try to find that. It's supposedly even more accurate that engine hours alone.
psneeld
Guru
Not sure where that bad info came from or how old it is....most modern marine engines nowadays are going much longer....inboard, outboard, gasd, diesel...etc...etc...
We routinely put over 5000 hours on gas inboards in the assistance towing fleet and beat the livin' crap out of them compared to rec boaters.
The trouble with just using hours is that itn is of little relavenvce to how old all the expensive parts that are bolted on to it or how it's been used/abused.
psneeld
Guru
I know Cat engines started using gallons through as a benchmark at least 10 years ago for estimating rebuilds...never could find it again in their internet literature though. I got it straigh from them when i was emailing questions about my 3208s
bfloyd4445
Guru
glad you said that. I had remembered numbers on gas police boats with engine replacement from 15 years ago and they were seldom replaced before 5000 hours and they are beat to h.
Chuck Gould
Senior Member
Well, you would be in a position to know, as you make your living towing in vessels with mechanical failures. I guess that the concept of gasoline inboards going 5000 hours, even when "beat to crap" is brand new to me. I wouldn't expect to be able to beat my diesel to crap and get that kind of service. That's a great thing to learn, so thanks.
Here's one possible source of the "bad information": From surveyor David Pascoe's web site:
"Performance Diesels Harken back to what I said about squeezing the maximum amount of power out of an engine block, along with what I said about cooling systems. I'm still stunned that I hear guys talking about diesel engines running 3, 4, even 6 thousand hours. I can count the number of engines I've seen with 3000 hours on them that have never been rebuilt on the fingers of one hand. And virtually every one of them were in slow speed, long range cruisers with superb maintenance. I raised a lot of flack from my previous article in which I stated that the AVERAGE diesel runs about 1000 -1100 hours before overhaul. I stick by that number, but you have to understand that the AVERAGE includes high performance diesels, as well as those folks who do not maintain their engines at all; the ones who run them until they stop.
High performance diesels cause a tremendous drop the average since the go fast diesels often go bang at 600 hours or less. If anyone would like to challenge that, take a tour of the Fort Lauderdale diesel shops and check out the hour meters on some of these boats. You'll find many of them are less than two years old.
Diesel engines are capable of having a long life when the power to displacement ratio is low. But when they start jacking up the power, beyond what the manufacturer originally intended, that benefit disappears. There is a very simple formula you can apply to estimate service life: simply multiply the cubic inch displacement of the engine times one. The result is the maximum amount of horse power you can have and still expect a reasonable service life. A 6V92 engine is 552 CID; at powers greater than 550, these engines don't last. At 450, they'll go 10 - 15 years easily.
We recently surveyed a yacht with a pair of 8V71N (naturally aspirated) Detroit Diesels rated at 325 hp that hadn't been overhauled since new 1981. Now, an 8V71 has a 568 cubic inch displacement; the fact that these engines have a 0.56:1 power/displacement ratio explains why they could run so long.
Conversely, divide the CID by the horse power, and the greater the result UNDER the factor of one (1), the longer engine life you can expect. If you have an engine with an 0.70 CID/HP ratio, then you can expect 3000 hours engine life. Otherwise, you are a victim of the myth."
