Lehman 120 Exhaust Elbow Replacement - Is It Time?

[catalinajack]

My elbows are five years old with about 1,000 hours use. Should they be replaced as preventive maintenance? I have no signs of leakage.

 

[kchace]

That’s starting to get up there. They can fail internally with no external signs. I would at least remove and examine them inside.

Ken

 

[Larry M]

I’d just replace them. We lost an engine on our last boat because we didn’t change the elbow. The water injection port into the elbow corroded through. When we’d shut off the engine, water would run into the last cylinder via one of the valves. The valve stem corroded and broke off. We were able to rebuild the engine but it would have been cheaper to replace the $200 elbow. This is the head of the valve after it bounced around in the cylinder before we were able to shut it down.

 

[Busterbrown]

I was told replace every six years? I’m curious to see what Ski has to say He has probably replaced hundreds

 

[rgano]

I was told replace every six years? I’m curious to see what Ski has to say He has probably replaced hundreds

In 29 years, I replaced mine three times on my twin 120s; once when I replaced the corroded mufflers above the engines early on, and twice when I saw signs of leakage onto the top of the heat exchangers. Given the valve issue mentioned above, I do however, think every 5 years is a good plan. I found that the lower right hand bolt head required a ground-down wrench for removal, and you really should put some anti-seize on all four bolts. I broke one once and required the assistance of a mechanic with an oxy torch to remove it, one of two or three times outside assistance ever walked aboard my boat.

 

[jungpeter]

Hi Catalinajack,

My personal rule of thumb is to remove, clean, bead blast, and inspect my risers every five years, on both my main engine(s) and gensets. Regardless of engine hours, and regardless of material. Inevitably, after these inspections, I've discovered I had to replace 'em at ten year intervals. Sometimes I can save the old ones as spares, but end up junking them sometime thereafter, as they're simply taking up space.

Again, in my personal opinion, a five-year replacement interval for risers is a bit steep for recreational use. I've gotten better service life than that, over several decades of experience. Risers, heat blankets, and the labor to remove and inspect are tough enough nuts to cache. Adding the cost of NEW risers to that total is a bit spendy.

AND, I've gotten a few "holy $%^&, look at THAT" moments upon inspection (particularly on a new-to-me boat) that prompted an immediate deep dive into my back pocket for yet another (few) thousand. Money very well spent, as I've never lost an engine (knock on wood) to date due to riser issues.

Regards,

Pete

ps-risers seldom give you an external indication of failure. It's almost always inside, where you can't see the failure, unless you remove the silly thing.

 

[Comodave]

If you are worried about them go ahead and replace them. They have had a good long life. Who knows how long they will go. If you wait 1 hour too long what are the consequences? Rebuild the engine... After 1000 hours you have gotten good value from them.

 

[warfdog]

I would replace them. Otherwise you will likely face the same situation as I have... On a naturally aspirated Lehman it's not a big task and replacements are only $200 per engine.

 

[SteveK]

I’d just replace them. We lost an engine on our last boat because we didn’t change the elbow. The water injection port into the elbow corroded through. When we’d shut off the engine, water would run into the last cylinder via one of the valves. The valve stem corroded and broke off. We were able to rebuild the engine but it would have been cheaper to replace the $200 elbow. This is the head of the valve after it bounced around in the cylinder before we were able to shut it down.

As said inspection can't hurt.
In your case how did the water flow into 6th? To rephrase, I know exhaust manifold, open valve. What I am wondering since the outlet is higher than manifold once the engine stops there should be no flow. When engine is running the exhaust should keep water heading out.
My guess, trying to get confirmation is it entered during cranking, before starting. That was explained before here, if it does not start right away, shut the intake thru hull.

 

[kchace]

Steve I believe the problem occurs when the mixer elbow corrodes through near the top. On shutdown, residual water dribbles through the hole and into the manifold and through a possibly open exhaust valve. Would only take a few drops left sitting there for any length of time to cause cylinder problems.

Ken

 

[catalinajack]

I just removed one elbow. It still has some life in it. Tomorrow I am driving down to American Diesel to pick up two new elbows. Based on my experience it looks like, on this boat, exhaust elbows should last more than five years and 1,000 miles. I am a great fan of replacing parts before their time. I don't care about squeezing that last bit of use from anything boat or vehicle.

 

[SteveK]

I just removed one elbow. It still has some life in it. Tomorrow I am driving down to American Diesel to pick up two new elbows. Based on my experience it looks like, on this boat, exhaust elbows should last more than five years and 1,000 miles. I am a great fan of replacing parts before their time. I don't care about squeezing that last bit of use from anything boat or vehicle.

Is a picture possible of the inside? New compared to old.

 

[catalinajack]

I will post before and after pics in a couple of days. Am getting the new elbows tomorrow.

Is a picture possible of the inside? New compared to old.

 

[catalinajack]

No pictures. I was unable to sufficiently light the inside of the elbows to get a decent photo. I think most would agree, however, that the elbows still had a lot of life left in them. Having already removed one, I elected to replace both rather than just one or reinstalling the one I had removed. I already had new elbows in hand. Getting the 3.5 inch hose off the the elbows proved not as difficult as I had anticipated. Also, because over time, every six months or so, I had loosed the mounting bolts and re-tightened, with anti-seize, getting those bolts out was no problem at all.

 

[Jango]

My last trawler had a Perkins with stainless elbow. I’m lack knowledge on the Lehmans but they and Perkins would be a prerequisite on my next trawler. Do they not make them in stainless and if so would the extra cost be worth the benefit?

 

[Larry M]

My last trawler had a Perkins with stainless elbow. I’m lack knowledge on the Lehmans but they and Perkins would be a prerequisite on my next trawler. Do they not make them in stainless and if so would the extra cost be worth the benefit?

You can buy a SS elbow for the FL SP135 but I haven’t seen one for the FL120.

 

[SteveK]

No pictures. I was unable to sufficiently light the inside of the elbows to get a decent photo. I think most would agree, however, that the elbows still had a lot of life left in them. Having already removed one, I elected to replace both rather than just one or reinstalling the one I had removed. I already had new elbows in hand. Getting the 3.5 inch hose off the the elbows proved not as difficult as I had anticipated. Also, because over time, every six months or so, I had loosed the mounting bolts and re-tightened, with anti-seize, getting those bolts out was no problem at all.

Thanks for trying.

 

[syjos]

I'm on my third elbow in 20 years. Around 5 to 7 years between replacement.

My elbows always start leaking on the exterior. I use the 3" elbow.

The elbows on FL 120 are so inexpensive that replacement is not as painfull as other engines. Previous boat with a Perkins 63544 required a stainless steel elbow that cost $1300 to have made in 1990.

 

[cdsailor]

I’m curious if anyone has an idea of Lehman 120 elbow lifespan in freshwater. I suspect that makes a fairly significant difference. Anyone know?

 

[Alisske]

I read somewhere to replace every 2 years.

That being said, I replace every 3 years. (I went 2 years in the first one, looked at it when I replaced it and thought it had life in it.). I went 4 years in the second and the “shelf” in the elbow was thin, but I could have squeezed another year out of it.

I’ll take pics when I replace. I think every 3-4 years is a good measure. If I’m taking the trouble to take it off, might as well replace it. I purchase mine on eBay (new) for about 125$ shipped. (Maybe bomac marine).

In any case, that’s in the northeast in saltwater.

I think the most corrosive aspect to the shelf is being superheated and cold water pouring on it. (But I’m not a metallurgist, lol)

I’ll post some pics. Was gonna do it this weekend. (Painted it Lehman red last weekend)

 

[catalinajack]

According to Brian Smith (American Diesel), the useful life is 1,700 hours.

I read somewhere to replace every 2 years.

That being said, I replace every 3 years. (I went 2 years in the first one, looked at it when I replaced it and thought it had life in it.). I went 4 years in the second and the “shelf” in the elbow was thin, but I could have squeezed another year out of it.

I’ll take pics when I replace. I think every 3-4 years is a good measure. If I’m taking the trouble to take it off, might as well replace it. I purchase mine on eBay (new) for about 125$ shipped. (Maybe bomac marine).

In any case, that’s in the northeast in saltwater.

I think the most corrosive aspect to the shelf is being superheated and cold water pouring on it. (But I’m not a metallurgist, lol)

I’ll post some pics. Was gonna do it this weekend. (Painted it Lehman red last weekend)

 

[Alisske]

According to Brian Smith (American Diesel), the useful life is 1,700 hours.

Interesting number “1700”. I suppose if it’s hours versus years, maybe the heat/saltwater Combe is driving the corrosion pace.

I mean, when I bought my boat it was 20 years old with 1600 hours. The elbow was shot though.

Go figure.

 

[syjos]

According to Brian Smith (American Diesel), the useful life is 1,700 hours.

I think 1700 useful life is debatable. A boat in the water all year gets salt build up in the elbow rusting it out faster. Replacement at 1700 hours is pushing it unless an owner racks up unusually high hours yearly.

I've been averaging between 800 and 1100 hours between elbow replacement. As I stated earlier, the two times I had to replace the elbow, the elbow was starting to weep rusty water from the exterior of the elbow.

An elbow on a boat hauled every winter should last much longer as long as the engine is flushed with fresh water at layup.

 

[ScottC]

I'm 10 years (1400 hours) on my exhaust elbow and, until this thread, I had no clue these things should be replaced so frequently. I mean, how much can go wrong with a stupid elbow??!! Anyway, the boat yard storing my boat (while I can't access it during these Corona times) said it I should keep an eye on it. I told them to take it off and inspect it. Now, after what I've read here, I expect they will be replacing it! Thank you for this valuable discussion!

 

[syjos]

I'm 10 years (1400 hours) on my exhaust elbow and, until this thread, I had no clue these things should be replaced so frequently. I mean, how much can go wrong with a stupid elbow??!! Anyway, the boat yard storing my boat (while I can't access it during these Corona times) said it I should keep an eye on it. I told them to take it off and inspect it. Now, after what I've read here, I expect they will be replacing it! Thank you for this valuable discussion!

We are talking about Ford Lehman cast iron elbows that are replaced more frequently. Your engine will have a different type of elbow that will have it's own service period.

 

[ScottC]

Mine is a VW Marine diesel. Now marketed under CMD, I believe. I don't think mine is cast iron, but nevertheless, this discussion has been an eye-opener and a learning experience for me. Even if I'm on a different replacement schedule, I'm now at least aware that there should be a replacement schedule!!

 

[Alisske]

Mine is a VW Marine diesel. Now marketed under CMD, I believe. I don't think mine is cast iron, but nevertheless, this discussion has been an eye-opener and a learning experience for me. Even if I'm on a different replacement schedule, I'm now at least aware that there should be a replacement schedule!!

The issue with the Lehman elbow is because there was is a shelf in there that the cooling water pours into and it’s directed down the exhaust pipe versus going down into the manifold/cylinder. When the shelf rots out, it dumps sea water right into the exhaust manifold and into the cylinder when you stop the engine.

When I bought my boat, the shelf was rotted out. I had to replace the exhaust manifold because it got rotted near #6 cylinder due to water pouring on it. (That was a 1600$ replacement).

I redid the engine head Gasket prophylactically since I redid the top of the engine, and the #6 cylinder looked good.

Really only a Lehman 120 thing. Your probably good to go.

A

 

[catalinajack]

I was just relaying what Brian Smith had to say. In fact, I replaced mine at 1,000 hours and they did have some Life left in them, parhaps as much as 500 hours. Who knows? I don't regret changing them out even if it was a bit early. Seems, though, they will last at least 1,000 hours.

I think 1700 useful life is debatable. A boat in the water all year gets salt build up in the elbow rusting it out faster. Replacement at 1700 hours is pushing it unless an owner racks up unusually high hours yearly.

I've been averaging between 800 and 1100 hours between elbow replacement. As I stated earlier, the two times I had to replace the elbow, the elbow was starting to weep rusty water from the exterior of the elbow.

An elbow on a boat hauled every winter should last much longer as long as the engine is flushed with fresh water at layup.

 

[rolomart3]

My elbows are five years old with about 1,000 hours use. Should they be replaced as preventive maintenance? I have no signs of leakage.

Absolutely and positively yes. If I remember correctly, the part cost less than $100. It rusts in place regardless of usage.

I replaced mine in about 2 hours plus wait time instead of 15 minutes because the bolts were rusted--another reason for periodic replacement.
It all began while cruising, the exhaust elbow developed a serious leak and out of nowhere my bilge pumps turned on. Slowly ( 1000 rpms) limped back to port with the weekend ruined.

Conclusion: after 5 years the options are 1) inspect and replace, or 2) replace.

Note: Be very gentle with the bolts. You may need to use softening and antirust products and or apply heat with a torch (fire extinguishers within hand reach).

There may be differing opinions. This is mine based on experience.

 

[warfdog]

Here is an example of the internal condition of the exhaust elbows on my boat, which I recently described the engine seizing due to water leaking on the the #6 piston of my Lehman 120.

First pic is old and new elbows - no apparent flaws, or difference, in the old elbow from external appearances except for the new coat of paint on the new elbow. The second and third pics are the inside of the old and new elbows, and the last picture is the 2 lbs. of rust and scale that I knocked out of the old elbow.

The build up of scale and rust on the floor of the elbow combined with the 70% wasting of the raw water shelf in the elbow led to water flowing backwards into the exhaust port and #6 cylinder at shutdown, damaging the head and piston.

You can NOT tell externally when an elbow has failed, nor are there any signs of age externally. In salt water it is a very good idea to just replace elbows every 3-5 years considering what an inexpensive maintenance item it is...