Lehman 120 Exhaust Elbow

slowbutsteady · May 27, 2021

Greetings! I have a new to me 1981 CHB 34 tri cabin with its original Lehman 120 with hours just shy of 4000. The boat had meticulous maintenance records until 2011 but the PO I purchased from only had professional mechanics work on his boat (a good thing) but didn't save all the receipts. So I've spent the past 6 months prioritizing my engine maintenance plan based on what I can see and what is most critical for the engine health. I had a mechanical survey done and the engine was reported to be good condition.

Since they are expendable parts that will fail with enough time and not terribly expensive I'd like to replace the oil, transmission, and coolant heat exchangers and the exhaust elbow. Id prefer to spread that over two seasons if I can.

Sharing a few photos of some bottom side exterior corrosion on my exhaust elbow and trying to figure out just how concerned I should be about this before I do a summer of cruising before my next round of engine maintenance. Any opinions on the condition of this elbow from the outside? I see some corrosion on the engine side, which may be a result of an elbow left on too long in the past, but I don't see any leaking, exhaust or wetness while operating the engine currently. I have good water flow from the exhaust and zero overheating issues. No steam or excessive smoking. I'd like to keep it that way!

alormaria · May 27, 2021

Looks new to me. If it ain't broke, don't fix it.

Comodave · May 27, 2021

Can you get the hose off it to look up inside it and see how rusty it is inside?

slowbutsteady · May 27, 2021

@comodave - I probably can but not without some considerable effort (then again, what job in boating doesn't require some cussing and bloody knuckles).

You know how hoses are - you take em' off and usually just have to replace them after working them so much. If I'm fiddling with it that much I might just replace the elbow at that point. I've heard horror stories about the interior failing and cooling seawater working its way back in to the #6 cylinder. Sounds like a good way to kill an engine quickly.

Just hoping I can get through the summer first before I start taking parts off!

kchace · May 27, 2021

The elbows don't look too bad, but the problem is that the real corrosion is going on inside. The only way to be sure is to pull the hose and look. I will say that in my experience, exhaust hoses are usually not too hard to get off.

Ken

RT Firefly · May 27, 2021

Greetings,
Mr. s. As mentioned, doesn't look bad from the outside, at all BUT....Perhaps purchase a replacement WITH the necessary gasket AND the injection fitting (small hose) and have it on board as a spare which you fully intend to change out after this season. In the chance it goes south (perish the thought) you'll have everything at hand to do a repair. You're gonna buy the stuff anyway.
Finally. Assemble the injection fitting on the elbow and give everything a coat of red paint.

Alisske · May 27, 2021

kchace said:
The elbows don't look too bad, but the problem is that the real corrosion is going on inside. The only way to be sure is to pull the hose and look. I will say that in my experience, exhaust hoses are usually not too hard to get off.

+1. Outside tells you nothing. When the shelf rusts out the water can pour into cylinder 6. I don't think thats fatal for the engine or anything, but why not check?,

I would buy a new elbow and gasket and then check it visually. If its bad, or questionable, you got the parts while you have it apart. If you don't need it this season, you'll need in the next few seasons. .(its cast iron and it is not going to go bad, lol)

I check mine every two years and replace in the third year. I actually unbolt it from the manifold and just replace the gasket when I check

FYI - When I replace the elbow, I rotate the upper bolts down to the lower bolts and then replace the top ones with new bolts. (In my engine, the lower 2 bolts always get the most corroded, tops look like new)

Marco Flamingo · May 27, 2021

I should send you a picture of my exhaust elbow and then you would feel much better. I am sure that the inside of mine looks better than the outside because it would not be possible for it to look worse.

BruceK · May 27, 2021

One of mine began to "sweat"/ leak moisture. Waiting for new ones to from USA I patched the defects with epoxy putty,finding surprising numbers of rusty spots working my way over it. Had to be coming from inside. The putty was very effective, it`s short term backup you could carry.
Yours looks ok, but if you are going to pull to inspect, I agree, replace it. ADC and Fredwalker1 are good sources.

Comodave · May 27, 2021

Mine are stainless. We had to pull one to get the exhaust aligned when I reinstalled the starboard engine. When I put the port engine back in I didn’t have to pull it though. It was very easy to get off since the exhaust hose was already off. I did spray PB Blaster on the bolts before I tried to take them off. Interestingly there was no gasket in between the elbow and the turbo. Brian sent me a metal gasket to put in. If you take the bolts off the elbow it will likely twist out of the exhaust hose. Good time to look at the hose clamps on the exhaust.

BeeJay · May 28, 2021

Change it now. It’s not going to save you any money because you’ll be doing it next season anyway, and because you’re asking you I bet that you’ve already got that uneasy feeling. I had one that was leaking a little and I decided to cast a new one in stainless steel. As it took a little time to track down the original pattern and I didn’t want to miss any time on the water I had the original welded up. It worked out fine and I replaced it with my new cast stainless elbow a couple of months down the track - job done, all sweet. Well you know the saying ..... “you don’t know what you don’t know”. I found the old unit that I removed and left laying about in the shed, I really dodged a bullet. I’ll post the pictures it might sway you, however mine would drip a spot of water every now and then so maybe worse than yours.

Cigatoo · May 28, 2021

One of these should work. Stainless will last a lot longer.
https://hdimarine.net/?s=Lehman&post_type=product

BeeJay · May 28, 2021

catalinajack · May 28, 2021

Anti-seize on the four bolts! Once a year, I loosen and retighten the bolts.

Alisske said:
kchace said:

The elbows don't look too bad, but the problem is that the real corrosion is going on inside. The only way to be sure is to pull the hose and look. I will say that in my experience, exhaust hoses are usually not too hard to get off.

+1. Outside tells you nothing. When the shelf rusts out the water can pour into cylinder 6. I don't think thats fatal for the engine or anything, but why not check?,

I would buy a new elbow and gasket and then check it visually. If its bad, or questionable, you got the parts while you have it apart. If you don't need it this season, you'll need in the next few seasons. .(its cast iron and it is not going to go bad, lol)

I check mine every two years and replace in the third year. I actually unbolt it from the manifold and just replace the gasket when I check

FYI - When I replace the elbow, I rotate the upper bolts down to the lower bolts and then replace the top ones with new bolts. (In my engine, the lower 2 bolts always get the most corroded, tops look like new)

Click to expand...

Tator · May 28, 2021

Went to replace mine a few weeks ago on one of my 120 Lehmans. Top bolts came out fine but, bottom bolts wouldn't budge even after soaking with Kroil oil (I'm not sure the oil could seep past the washer and thickness of the flange to reach threads). Obviously, anti-seize wasn't used and the access to the bolt heads was difficult. As it was more of a maintenance issue and I figured I would have to cut off the lower bolt heads, I've delayed the project until I had more down time. Be prepared for this possibility.

Tator

sean9c · May 28, 2021

These guys are right down the street from the OP, call them
https://www.nationalmarineexhaust.com/

Xlantic · May 28, 2021

At least it is not the original elbow. It is an American Diesel replacement so it may not be that old. And it does look pretty solid.

Replacing it with a new one, just to be safe if you don't know how old it is, would only cost you a couple of hundred bucks for the parts. If the bolts come out easily it is an easy repair. If one breaks, it is a PITA. Given the elbow has been replaced once you might get lucky with the bolts.

Getting raw water in your cylinder is to be avoided. Ask me why I know ...

BeeJay · May 31, 2021

Hey Xlantic - I think Halcyon strikes a hansom figure in your Avatar, nice looking wagon to my eye.

Xlantic · May 31, 2021

BeeJay said:
Hey Xlantic - I think Halcyon strikes a hansom figure in your Avatar, nice looking wagon to my eye.

Thank you, Beejay.

The hull was originally white but a few years ago, when it needed to be re-painted, we went with flag-blue. I think this visually stretches-out the boat, making it look a bit sleeker and less bulky than in the original white.

Pete Meisinger · May 31, 2021

Personally, I would buy new elbows and gaskets but I would NOT install them. Keep them for when the present ones fail. This forum is literally full of members who are asking for advice on how to get broken exhaust elbows out of the manifold, etc. It can be an easy job but it can be a real pain.

Why not get new ones and give the old ones a substantial rap with a hammer. It might tell you something. And since you will have to remove the exhaust host anyway to replace them, I agree that you should take a look inside.

But my best advice is to leave them alone.

If, and when they fail, it will not be a catastrophic failure. It won't damage your engine or boat. The cabin and engine compartment may get smelly or wet but you will be able to get to port or finish your trip.

pete

Alisske · May 31, 2021

I just wanted to repost Cigatoo’s link to the stainless elbows. https://hdimarine.net/?s=Lehman&post_type=product%5B/url

I cannot believe i did not realize they made that elbow in stainless! I have to admit I almost did an impulse purchase, lmao. Thanks for posting Cigatoo.

The 2715 is not listed as a one of the engines in the product description, but it looks like a duck, walks like a duck, quacks like a duck, so to speak, so it must fit the 2715.

Are there downside to stainless? I know that sort of a dumb question, but since i am gonna spend an 80% premium for stainless, just wanted to make sure its worth it.

Thoughts?

Cigatoo · Jun 1, 2021

Pete Meisinger said:
Personally, I would buy new elbows and gaskets but I would NOT install them. Keep them for when the present ones fail. This forum is literally full of members who are asking for advice on how to get broken exhaust elbows out of the manifold, etc. It can be an easy job but it can be a real pain.

Why not get new ones and give the old ones a substantial rap with a hammer. It might tell you something. And since you will have to remove the exhaust host anyway to replace them, I agree that you should take a look inside.

But my best advice is to leave them alone.

If, and when they fail, it will not be a catastrophic failure. It won't damage your engine or boat. The cabin and engine compartment may get smelly or wet but you will be able to get to port or finish your trip.

pete

If you are lucky it will rust through when it fails. Worst case it clogs with rust / rot and backs up salt water into the engine. I would consider that catastrophic. I bet the engine would agree.

Xlantic · Jun 1, 2021

Alisske said:
I just wanted to repost Cigatoo’s link to the stainless elbows. https://hdimarine.net/?s=Lehman&post_type=product[/url

I cannot believe i did not realize they made that elbow in stainless! I have to admit I almost did an impulse purchase, lmao. Thanks for posting Cigatoo.

The 2715 is not listed as a one of the engines in the product description, but it looks like a duck, walks like a duck, quacks like a duck, so to speak, so it must fit the 2715.

Are there downside to stainless? I know that sort of a dumb question, but since i am gonna spend an 80% premium for stainless, just wanted to make sure its worth it.

Thoughts?

Stainless can be treacherous due to crevice corrosion which happens in corrosive environments with little oxygen.

The photo below is a shaft key from a Groco Model K manual head. It has spent many years submerged in an oxygen-free, corrosive

environment and corroded significantly. The bronze shaft to which it was attached was in good shape.

I don't know if crevice corrosion can be an issue in exhaust elbows but would suspect American Diesel has an opinion on this.

SoWhat · Jun 1, 2021

Elbow looks new but as suggested, pull exhaust hose off to check.
The anti-seize suggestion applies to any bolt anywhere near the rear of the engine.
The drips from the shaft turn into a fine salt mist and instant rust.
I would add hoses and clamps to your replacement budget.

Sangraal · Jun 4, 2021

As others have said buy a replacement Stainless one. Once you have bought it I would install it. If you wish to carry an emergency spare perhaps hang onto the old one. Waiting for it to fail is in my opinion a risky strategy and one that’s has little merit and the cash has already gone out of the boat account for a new one. I changed mine along with all the coolers, fluids, belts, etc when taking over custody of our boat. Of all the things that can and will go wrong I try and eliminate the easy stuff. What ever you choose, good luck!

HypnoBob · Jun 4, 2021

For all things Lehman Ford, contact American Diesel. (804) 435-3107
Also, on their website they've got a lot of information about all these engines.

For those of you not familiar with them, Bob Smith was CEO of Lehman Ford USA. He worked with Roger Lehman to marinize the Ford tractor engine. I took his diesel engine class at TrawlerFest many years ago. Bob's deceased.

For many years, Bob wrote the Engineers Corner Q&A in the MTOA magazine (Marine Trawler Owners Association). I know he's addressed the elbows many times with pictures.

American Diesel is now in the hands of his son, Brian. They have all the parts, specs, tips and tricks, and so on about the engines. After Lehman Ford discontinued production, Bob started building the American Diesel engines with all the improvements developed over the years. He built about 100 engines a year.

Everybody had Bob's phone number, you should have American Diesel's on speed dial. LOL

83GB · Jun 4, 2021

Lehman elbow

Taking the elbows off can be a challenge. Years ago, I replaced mine and broke one of the bolts off. I tried everything with no success. $200 later a professional with an acetylene torch got it out. When I installed with new ones, I used anti seize. Last year, I replaced those ones. Again, one of the bolts would not come out but I did not break or strip the head. I ended up using an air powered impact wrench and that worked. I would recommend the impact wrench. Start with low torque and build up as needed...

IWAB · Jun 4, 2021

Exhaust risers

On my 120 Lehman’s I have Chrysler type exhaust risers. Knowing they are guaranteed to rust through, I installed new ones. Here is what one of the old ones looked like:

IWAB · Jun 4, 2021

We had to cut one of the bottom bolts on the adapter between the Lowe elbow and exhaust manifold. Don’t forget to chase the female threads on you exhaust manifold before installing the new elbow.

catalinajack · Jun 5, 2021

The key to ensuring those bolts come out easily is, indeed, an anti-seize compound but that is not enough. Once a year, sometimes sooner, I loosen the bolts and retighten. Do not expect them to not possibly to become seized again after many years in place. Takes maybe 10 minutes to do both engines. They loosen quite easily every time I do it.

83GB said:
Taking the elbows off can be a challenge. Years ago, I replaced mine and broke one of the bolts off. I tried everything with no success. $200 later a professional with an acetylene torch got it out. When I installed with new ones, I used anti seize. Last year, I replaced those ones. Again, one of the bolts would not come out but I did not break or strip the head. I ended up using an air powered impact wrench and that worked. I would recommend the impact wrench. Start with low torque and build up as needed...

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