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Old 01-03-2015, 02:58 PM   #1
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Exhaust elbow on Lehman 120 - concern

I have a 1986 GB 42 with 2 Lehman 120s. see photo of the one that has exhaust elbow looking burnt and different than other engine. Yet both engines run 175-185 degF and cooling systems appear to be fine. Should I be concerned about how this exhaust elbow "looks"? See photo. Thxs.
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Old 01-03-2015, 03:32 PM   #2
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You should remove it and inspect it for corrosion etc. as you can't tell from the outside until it has failed. When it fails, it will toast the rubber hose and perhaps the muffler so you will have to replace those too. You will probably fill the engine room with soot if the hose breaches. If the water supply is still running, you could flood the boat.
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Old 01-03-2015, 03:50 PM   #3
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Even though both engines run at normal temps, the one with the burnt exhaust elbow might be getting plugged with scale inside. This can cause a blocked flow path and localized overheating which may cause the discoloration you are seeing.

Another cause may just be low raw water flow due to a bad impeller or worn raw water pump, so check that first. If you can get a bucket under the exhaust outlet, measure how long it takes to fill on the port and starboard side at idle and compare. Any significant difference is either the pump or plugage in the raw water path, either the heat exchanger or the exhaust mixer elbow.

If you can buy, beg or borrow an IR gun, go out on the boat and get it up to your normal cruising rpm. Then shoot all sides, top and bottom of the exhaust elbow, port and starboard and compare the two. The exhaust water injection elbow can get hot on top which gets less of the flow, but shouldn't be more than 200 degrees. Check it right where the exhaust hose clamps. If it is too high it can also melt the hose.

If the temps are high, clean the inside or replace the elbow. Usually with a scaled up elbow the engine won't make rated rpm in gear and smokes a lot.

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Old 01-04-2015, 08:13 AM   #4
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I think you will find the elbow is toasted and its time to replace it. If you have twin engines guess what? Time for 2
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Old 01-04-2015, 09:08 AM   #5
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I think you will find the elbow is toasted and its time to replace it. If you have twin engines guess what? Time for 2
Correct. Wet exhaust elbows are a routine preventative maintenance item. Waiting for them to externally leak especially on an older engine can result in an issue or two you don't want.
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Old 01-04-2015, 12:18 PM   #6
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Indeed something is clogged and preventing proper water flow. full disassembly of the elbow is needed and probably replacement. The rubber hose needs careful inspection as well. Be sure to find the root cause as it could easily be the water pump, water inlet, strainer etc.
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Old 01-04-2015, 12:41 PM   #7
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Not all of that casting has a water jacket, so there will normally be some hot spots. Still a good idea to open it up and assess the condition.
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Old 01-06-2015, 12:06 PM   #8
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When we bought our Defever 44 last February, the surveyor noted the scorching of the underside of one of the exhaust elbows. I elected to change both elbows, kinda like when a front wheel bearing on a vehicle fails, the other is not far behind it. I acquired replacements myself as the change looked to be very straightforward except for the fact that the upper bolts ended up being "welded" into the head through heat and time. There was not enough clearance to get an impact socket onto the head of the bolt. Bottom line was I had to have a yard extract the bolts. The mechanic had to carefully drill them out. Those elbows were probably very old. If I were you I would replace both immediately but be prepared for difficulty extracting the upper bolts. BTW, the lower pairs came out easily. I double-checked with the mechanic that he used anti-seize on the bolts. I intend to remove the bolts every six months to apply new anti-seize, a fifteen-minute job at best. From my reading and research a bad exhaust elbow will sometimes lead to the overheating of the #6 piston, the one closet to the elbow. You do not want this to happen because bad things can happen very quickly. Can anyone else expound on this point?
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Old 01-06-2015, 12:20 PM   #9
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[QUOTE=catalinajack;296584]. BTW, the lower pairs came out easily./QUOTE]

LOL, on mine it was one of the lower bolts that I couldn't get out.

Since the lower part of the hot exhaust port on the manifold was partly eroded, I removed the manifold and had that surface milled (about 1/8 inch)
BTW my son got the remaining bolt out in about 10 seconds with a torch and vise grips.
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Old 01-06-2015, 05:43 PM   #10
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My insurer requires removing and inspecting the elbows every 5 years. I hope mine are still good 5 years from new.
Take care,there are 3 and 3.5'' Lehman elbows. Mine came from Fredwarner1,who sells on Ebay a range of Lehman cooling system parts. I had my mechanic view his site before ordering heat exchangers, oil coolers, and elbows, all worked out well. Of course AD has them too.
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Old 01-06-2015, 06:24 PM   #11
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Who's your insurer Bruce?
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Old 01-06-2015, 06:33 PM   #12
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Who's your insurer Bruce?
Club Marine (Allianz). It`s from memory, not checked the Policy wording recently. They were quite excited about me doing it when I bought too, I assume they`ve had claim experiences over failed ones.
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Old 01-06-2015, 08:11 PM   #13
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Hmm, I must check the fine print on my Club Marine policy.

I have a mate who works for Pantaenius and we were chatting the other day about Club Marine. He asked me how much the boat was insured for and promptly told me that there was no way they would pay the full insured value on my policy in the event of total loss.

In effect I was paying a $40K premium that would never be paid out on.I checked with Club Marine and they confirmed what he said. I promptly reduced my cover to what I thought would be an agreed market rate and reduced my insurance premium by about 30%.

FWIW, he said Pantaenius insure at an agreed value, not market rate and pay on that figure in the event of loss.
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Old 01-28-2015, 07:37 PM   #14
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Being one who has experienced a failed elbow I would highly recommend inspection or replacement if you have several years on the boat ,just to be on the safer side. I had what was mentioned as far as soot and water galore. I was going WOT when it happened , I do that now and then to see how the engines are running. Well not long into my WOT I soon discovered a major bog down to my port engine, I still remember the RPM's , it was at 400 down from 2500.


I began to throttle back and looked out the back and I had so much smoke I thought I lost a turbo. Once I got stopped and in neutral I went to open my engine room access panel, thank goodness it was in the aft and outside of the salon. When I opened the panel soot just poured out, I thought at first it was a fire. I had to wait for it to clear quite a bit before I could enter. Once I got down by the motors I saw where the wet exhaust had broke and fell to the engine room. The soot from the starboard motor had dumped the exhaust right into the intake of the port engine and that is what made the motor bog down, the filters were fouled big time. That is when I noticed the water, that freaked me out even more. Since I was just making a fuel run at the time I turned the boat around and heading back to our marina.

I replaced both wet exhaust elbows with custom made SS . I think I spent around 2 weeks in the engine room with rags and spray 9.
I know of one other boater this happened to and he filed a claim. Thinking back it might been the better route.

Our boat is a 1993 model, I think was around 2009 when one failed. That is also when learned more about wet exhaust elbows. I have a picture somewhere to show an area I cleaned on our Kholer Generator, one clean spot showed what an amazing mess I had on my hands.
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Old 10-27-2015, 07:13 AM   #15
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Hi. I'm having quite an issue with my 120 hp lehman. It first showed up as hydrolocking. I thought I had a battery issue but soon discovered not so. My antifreeze was replace with seawater. I ordered a head set from American diesel and removed the exhaust elbow and intake manifold. It seems the rear low cylinders were flooding. Ordered a new elbow and cleaned and reinstalled the manifold. Also checked and cleaned the heat exchanger. Not problem there. I ran the boat the other day briefly without filling the block with water. After setting a couple days I came back to fill the block first with fresh water flush and then antifreeze. Only to find the cylinders had sea water and hydro locked again. I took the new exhaust elbow off and the bottom of the flange on the head may be suspect as I didn't have it planed. I had taken the manifold into the shop but they couldn't check it for leaks. Now I'm thinking maybe my muffler is shot and allowing seawater in? This is a new problem for me.
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Old 10-27-2015, 07:26 AM   #16
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I took the new exhaust elbow off and the bottom of the flange on the head may be suspect as I didn't have it planed. I had taken the manifold into the shop but they couldn't check it for leaks
Do you mean the bottom of the exhaust manifold where it meets the elbow?
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Old 10-27-2015, 08:20 AM   #17
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Yes the bottom of the manifold. I used the new gasket and permatex on both sides I have it part again and will put a new gasket in and buff that flange better but I just thought maybe the muffler was restricting the water and it is backing up into the manifold and hydro locking. No reason for the salt water to get there. From the raw water pump to the x changer to the elbow. Simple rite?
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Old 10-27-2015, 09:27 AM   #18
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Not an expert by any means, but if seawater is getting into the antifreeze and the cylinders I would suspect a blown head gasket or cracked head. My $ .02.
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Old 10-27-2015, 09:41 AM   #19
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Shouldn't be sea water in the head or block. It had to get in through the elbow or heat exchanger and it's good. Coolant in the cylinders I could see a cracked head. I don't have a steam or overheat issue. Stumped
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Old 10-27-2015, 12:54 PM   #20
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Post photos of exhaust system.

Generally, SW gets into engine coolant by a leaking heat exchanger. That is usually non fatal.

SW in cylinders usually gets into engine through the exhaust, either a rotted mixer or engine too low relative to boats outside water line. That takes some careful measuring and analysis to determine.

But right now you NEED to get that water out of cylinders and out of the oil or it will wreck the engine. Suck oil out of bottom of pan to get rid of water and get engine running with sea water turned off and impeller removed. Need to warm it up and dry out the cylinders. Change oil and repeat. Engine makes very little heat idling, just don't run it past normal temperature. Do this with coolant in the engine.

Is exhaust manifold sw or fw cooled? I think some old ones were sw, but not sure.
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