The useful life of a Lehman 120?

[Yachts66]

Yes, it's somewhat of a loaded question and is very dependent upon maintenance, but all things considered, what do you expect this magic number to be?

 

[Max1]

I've read on here that some of these Lehmans can run for up to 20,000 hours? Right now I'm sitting on an engine that's at 3,000 hours, and I'm hoping that 20,000 hours is right. In the meantime, I do my best to do my oil changes, valve adjustments, and inspections on schedule. I got to make my baby last. How many hours on yours?

 

[mvweebles]

Really hard to say because so few wear out - there are a ton of traps that relegate an engine to the graveyard long before they're worn out. I'd guess fewer than 2% of the old low-displacement naturals like the Ford Lehman get worn out (and even 2% might be high). Of those 2%, I'd reckon 15k hours is the magic number before some sort of overhaul is needed. Some make it to 20k, others only 10k-12k.

 

[READY]

No magic number for any engine but Lehmans tend to do well as they are very simple, rugged and often not run hard. Pete's point is spot on. Also low cost (relatively) to overhaul vs many other brands.

 

[Mambo42]

Good part is that, if you take good care of them, you don't need to worry about them at all.
When I bought my boat the engines were running pretty bad, making a lot of noise, so I did a boroscope and as it turned out each cylinder was full with carbon build up. The valves were dirty and lots more.
I had the engines cleaned, put back together again and they were running perfect, had about 6000 hours on the counter, not a scratch on the cylinder walls. Until..............an angry mechanic, who did not get the job he had hoped for (I hired a FL specialist) decided he would make sure my engines would never run again. And so I had to buy 2 new engines. If it would not have been for this idiot my old engines would have run for thousands of hours more.
My new engines now have about 700 hours, I change the oil every 200 hours, the fuel pumps every 50, change the filters, in other words do exactly what is required and according to the company that overhauled my engines I will be out of the run in period in about 200 hours. Then I can change to normal oil and they should outlast me. I will be long dead before the engines will be finished.
I spoke with Brian and according to him 6000 - 8000 hours is basically nothing. Just take good care of them and they will take care of you.

 

[Choices]

I am at 6000+. They are pampered. I expect 20k easy.

 

[READY]

Should emphasize that changing the oil in the fuel pump is very important. That is about the most expensive component to replace and you likely would have to go through a rebuild and that might take some time. If new boat/engine to you I would do the first change at 25 hours and see if there is much diesel in the oil. If not then run 50 hours before next change. If still no oil then you might consider going to 100 hour interval. But the process is actually very quick once you do it a time or two and uses less than 1 pint of oil so no reason to push it beyond 50 hours for boats that don't get a lot of hours monthly.

FYI I have 2 newly rebuilt pumps as spares and likely will proactively change out the ones on my engine in the spring. No indication this is really necessary but since I have no idea when the pumps were last replaced or serviced and engines are in the 5,000 hour range seems to be a reasonable thing to do.

 

[O C Diver]

The potential is very good, but reality isn't. It's near zero, the percentage of people who own their Lehman for 20K hours. So, most have multiple owners, with only one required to do near zero maintenance. Add to that most of the engines that could reach 20K hours, would likely be 30 to 40 years old.

There are a couple of areas that require additional attention. The injection pump comes to mind. Also maintaining and flushing the coolant passages. From what I remember, the rear most cylinder can have heat issues if the coolant system is significantly neglected.

Add to that the normal:
Change the oil and filter regularly
Keep the engine from overheating
Don't run it on the pin
Don't run it too slow
Do preventive maintenance not repair

So yes, the potential is 20K hours, but the average is probably well below 10K.

Ted

 

[Comodave]

Bob Smith told me that the watermen in the Chesapeake area bring their Lehmans in at 20K hours for a preventative rebuild. But those engines are run regularly and have good maintenance l

 

[alormaria]

Forever...

 

[Choices]

Sorry, mine is a 135 with the new pump design.

It is true, 20k hours takes a long time or must be commercial. Most maintained engines will easily put live the hull.

The Lehman is the small block Chevy of the Marine world. Relatively slow turning and mechanically designed. Easy to maintain since it is basically a tractor motor.

 

[slowgoesit]

You are getting pretty much the same info you got when you asked the same question on Cruisersforum!

 

[Andy G]

Sorry, mine is a 135 with the new pump design.

It is true, 20k hours takes a long time or must be commercial. Most maintained engines will easily put live the hull.

The Lehman is the small block Chevy of the Marine world. Relatively slow turning and mechanically designed. Easy to maintain since it is basically a tractor motor.

I could well be wrong however, I was under the impression the Ford engine was a circa 1959 British truck engine that was mostly used as a static generator,as it was not particularly suited to truck work.

As I said I could be quite wrong about that though.

 

[Mambo42]

I could well be wrong however, I was under the impression the Ford engine was a circa 1959 British truck engine that was mostly used as a static generator,as it was not particularly suited to truck work.

As I said I could be quite wrong about that though.

My FL mechanic in Greece is a former truck mechanic and back in the days (80's) in he received his initial training on these engines. He told me that, especially in the UK, these engines were widely used in trucks. The drivers were never careful with them, was basically starting them up and instantly applying max power. So no careful warming them up and only then applying power.
According to him they last forever.

 

[DavidM]

One thing that contributes to its long life is its low hp relative to its displacement: 120 hp from 6.2 liters or about 20 hp per liter.

Diesel guru Tony Athens says that marine engines that are operated (not rated) at 30 hp per liter or less can have a long life. The Lehman 120 is probably operated at more like 60 hp, so that results in 1/3 of Tony’s recommendation.

So it “can” live a long life if operated and maintained conservatively.

David

 

[slowgoesit]

Wow, David
I guess our engine will last forever! at 13.93 liters, and 172 hp, the ratio on our Gardner 8LXB is 12.35 liters/HP!
But I agree, FL 120's and 135's are great engines. IF you can find an exhaust manifold when yours fails . . . .

 

[DavidM]

Yes, Gardners run slow and are virtually indestructible, if… they are operated and maintained by the book.

Most marine engines die an early death as a result of poor operation and/or maintenance.

David

 

[SteveK]

The useful life is until they are stop working.
Many estimates of 20,000 hours before a rebuild as long as parts are available still useful.
When I sold the GB36 with 50 year old twin Lehman 120 the mechanic brought to check them over started and stopped them way too many times without letting them run. I was nearby and about to ask why when he stopped. Later the buyer said mechanic was not used to a cold engine that old starting without turning over several times.

 

[psneeld]

The start and stop theory of being bad for engine is great for the average boat owner...but my years around pro mechanics prove that it isn't that big of a deal as troubleshooting may require starting and stopping dozens and maybe dozens more times in less than one day.

If that worried about it...just change the oil and go on with it when done troubleshooting.

As many have posted...either an engine wears out or is killed. Killed is the usual recreational cause and I have heard many times that overheating is the culprit.

Based on my experience... most boat owners will kill an engine long before commercial operators wear theirs out. I knew that long before assistance towing proved it to me.

 

[Grand Illusion]

A few of the earlier responses have touched on a point that, for me, is almost the primary concern above most others - parts availability.

If an engine is understressed and of fundamentally good design, "how long will it last" on a practical level for the average boat owner really means, "how long will I be able to readily buy parts when I need them."

Those of us with Lehmans are very lucky to have a great resource in American Diesel, coupled with the number of these engines still in service making the spare parts business hopefully a relatively profitable endeavor for them.

A friend of mine asked a surveyor once, why do the Ford Lehmans still have such robust support for parts and service when so many others of the era may be equally simple, tough, and reliable - but are dead end engines due to a complete lack of available parts supply.

His response was essentially that the Fords didn't change much in design over a 25 year production span, whereas many others had several major revisions and would require a much larger parts catalog to support them all.

Whether that's true or not, for me the most important thing to watch when it comes to the longevity of these old engines is parts supply. As some touched on earlier, if you needed an exhaust manifold or injection pump tomorrow, what would you do? We're spoiled by the number of still available parts, but some are starting to get a bit thin on the ground already.

 

[HeartWarrior]

The potential is very good, but reality isn't. It's near zero, the percentage of people who own their Lehman for 20K hours. So, most have multiple owners, with only one required to do near zero maintenance. Add to that most of the engines that could reach 20K hours, would likely be 30 to 40 years old.

There are a couple of areas that require additional attention. The injection pump comes to mind. Also maintaining and flushing the coolant passages. From what I remember, the rear most cylinder can have heat issues if the coolant system is significantly neglected.

Add to that the normal:
Change the oil and filter regularly
Keep the engine from overheating
Don't run it on the pin
Don't run it too slow
Do preventive maintenance not repair

So yes, the potential is 20K hours, but the average is probably well below 10K.

Ted

Really well said Ted.

 

[HeartWarrior]

Really well said Ted.

 

[Don G]

The worst problem with these engines is that the temperature sender and alarm sender are located at the highest point on the engine. These work perfect only when the coolant is absolutely full. The most important thing to do is add a second temperature alarm sender in the side of the block where the drain plug should be, behind the alternator. The problem this corrects is when underway if you get a coolant leak or the heat exchanger fails with the coolant going out the exhaust you will not get an alarm quick enough and #6 cylinder seizes. Neither the temperature gauge or the alarm respond properly or quickly when they are not covered with coolant.
Most marine engines are built this way. The boat I have now has caterpiller engines and I replaced the block drain plug with a second alarm sender and simply connected it to the original alarm sender.

 

[oak_box]

On the injector pump oil change...

"Easy" is a function of where the engine is mounted. On my port engine, with the pump in the center isle between the engines - not a big deal. The starboard engine, with the pump between the engine and the starboard wall is a different story.

And don't even get me started on what a nightmare the starboard engine water pump is to work on!!

Other than that, my engines have 4600 hours, and I hope to get a LOT more life out of them, and am somewhat planning on them outliving me!

 

[JAllen]

Yes, it's somewhat of a loaded question and is very dependent upon maintenance, but all things considered, what do you expect this magic number to be?

Our Lehmans have ~7600 hours on them. Brian has told me we are about 1/3 of the way through the useful life. We do baby them and make sure all the mx is done on a regular basis. I can change the oil in the fuel injectors in under 10 minutes now. I tend to do that at about 40 hours.

 

[Toadhall]

I can change the oil in my injector in under ten minutes too.
Its the 2 hours it takes to get by old body to the injector and back out then the 3 days on Ibuprofen that's hard

 

[Cape Henlopen]

Yes, it's somewhat of a loaded question and is very dependent upon maintenance, but all things considered, what do you expect this magic number to be?

I have owned 5 and rebuilt two from the crank up. At 1800 or less rpm an easy 10000 hours.

 

[Captain DJ]

here is a good help DIY at adjusting valves on the FL120.

How many of you adjust your own valves?
Do you do it every 400 hrs.?

Mine is due with this year's maintenance and I am wondering if I should do it or pay someone that has more experience. I have replaced water pumps and coolant lines for transmissions as well as the normal oil and filter changes every season. I shoot for 100-150 hrs on oil & filter, and do the fuel pump oil about twice as often.

Anyone in the Olympia area you recommend to reliably do this? I might want to watch and learn before tackling solo. But I am on a budget so IF my buddies here tell me it is no biggie, I may go ahead and add this to my routine.

Thanks

 

[Nepidae]

Please when responding clarify your engine.
There was several mention of oil in the fuel pump. Some 120s need to do that my 135s don't.

I think that Most questions can be answered by the FL expert, Brian, at American Diesel.

There is no one who knows the FL like Brian.

Avoid confusion, call The Man.

 

[klee wyck]

One thing that contributes to its long life is its low hp relative to its displacement: 120 hp from 6.2 liters or about 20 hp per liter.

Diesel guru Tony Athens says that marine engines that are operated (not rated) at 30 hp per liter or less can have a long life. The Lehman 120 is probably operated at more like 60 hp, so that results in 1/3 of Tony’s recommendation.

So it “can” live a long life if operated and maintained conservatively.

David

I have counted on this idea. The Mercedes OM403 in LIBRA is 12 liters. On her pins she can pull only 26 hp per liter. As she is normally run, she pulls 8 hp per liter.
My land life lends alot of evidence to the statement that these simple industrial engines can last a very long time when run steady and at moderate loads. It is very common for us to get 20k and not uncommon for us to get 30K before engines need major work.
One mistake and that can change very quickly though. Under full load, the loss of oil pressure for 15 seconds can total a big engine that is working hard. 10 psi/1000 rpm and you are golden in most engines it seems.