Yanmar Elbows - Do these need replacing?

[garmstro55]

I have twin Yanmar 4LHA-STP engines on a Mainship I bought in 2018. Previous owner said the elbows were recently replaced but didn't have the exact dates.

Earlier this year a Yanmar mechanic was doing a valve adjustment and mention the elbows might need replacing by observing a small amount of external surface rust.

Yesterday I attempted to take one of the elbows off to inspect. Unfortunately is was stuck in the exhaust hose and I ran out of time to remove it. However, I did get a couple of photos looking inside the elbow.

I would appreciate any opinions as to the condition of the elbow as best as can be determined from the pictures. It looks ok to me but I am no expert.

Also to be noted, the elbow exhaust temperatures were measured last summer with an infra-red thermometer to be around 125 degress F. I was told by someone else that 190 to 200 was an indicator of a bad elbow, so is 125 an indicator of a good one?

Thanks.

 

[sickatea]

On my Yanmar 6lya-stp, I replaced mine at the 15 year mark and they were in great shape. I think yours look fine. If you decide to replace, get the HDI version. They were great to deal with and they look really nice installed.
Btw, the 4lya is a great little motor!!!

-Rich

 

[DavidM]

Those look like cast SS and the surface rust is from the steel casting tooling. Looks fine to me.

David

 

[DrissZougari]

I have helped a friend replacing his exhaust elbow and the mixing elbow on his Yanmar. Sir, yours is in great condition!

 

[garmstro55]

Thanks for the feedback. I appreciate it.

 

[firehoser75]

On the face of the 2 photos, I agree they "appear" fine. However, exhaust elbows are a "wear" item and require periodic replacement with a time frame that is dependent on a number of factors. On my boat, my "stock" Cummins SS elbow (at 16 years old) looked, from the exterior to be in good condition (almost brand new looking). However, I had installed an exhaust hose overheat alarm when I bought the boat and on the first trip of my summer season, the alarm sounded. I check with an IR temp gun and only the hose was hot (just over 200 degrees F in a couple of spots), while all other engine temps were very good. Looking inside the elbow, like your photos, did not show any obvious issues. However, after sending the elbow to the radiator shop for acid cleaning, removing the carbon buildup, it was apparent that the elbow was corroded through on the inside (a few pinholes), and this was affecting the "shower" spray causing the high hose temps.
Now the scary part. On my boat, and a lot of other boats as they came out of their factories, it had a poorly designed exhaust system that could be described as "doomed to fail". This meant that had my interior leaking gone on for a while undetected (and it could easily have done so if not for the exhaust hose temp alarm), salt water could have entered my turbo or even the exhaust system of my engine creating major damage!!!
There is a good article on Seaboard Marine (sbmar.com) under Tony's tips regarding this type of situation, and this issue is more common than you might think with many different boat builders. Is yours a "doomed to fail"?? Worth a look and some investigation for sure.

I replaced my "starting to fail" stock exhaust elbow with a custom made one to basically eliminate the "doomed to fail" aspect.
Photo attached of my stock white exhaust and my new "wrapped" exhaust as an example.

Since you are looking at this now, it is worth checking into it further??

 

[Delta Riverat]

I wouldn't worry about them. Bolt 'em back up and run! Look new with carbon and nothing else.

 

[Dougcole]

I replaced the elbows and mixers on my ‘05 4lha-stps about 5 years ago. I went with a cast stainless aftermarket elbow, I can’t really tell from your photos, but yours appear to ve stainless, which would be a good thing.

My old elbows were original to the engines, yanmar oem. They were still mixing/cooling fine, but were leaking some exhaust around the seam between the elbow and the mixer, it was pretty obvious.

Id check the temp of the hose just downstream of the mixer and look very closely for exhaust leaks. If both of those tests are ok, Id run with them for another year or so and check them again. They look good to me.

 

[firehoser75]

Exhaust elbows can look "fine", and may even be "fine", but if they are of the type shown in the first photo in post #6 and if they are installed in that manner, you essentially have a "doomed to fail" setup. In essence it is only a matter of time, when, not if. With that setup under the "right" (wrong) circumstances, even having the boat lift operator lift the boat in a bow down angle (by mistake) could result in water entering the engine. When the interior (unseen) portion of the elbow corrodes through (even small holes) near the water injection point, water could enter the turbo (if equipped) or the exhaust manifold of the engine potentially resulting in severe engine damage.
Many on the forum probably already know about this, and/or have changed their setup to avoid this issue. However, my intent is to empower those who have not thought about this with the awareness and interest to investigate further to (potentially) save themselves from the headache and large expense involved should it happen to them. This "doomed to fail" design and setup should be considered (and changed as necessary) even if the elbow "looks and/or is" good.
Much more "technical" info is available for free on Seaboard Marine's (Tony Athens) website sbmar.com under Tony's tips and in the free forums.

 

[boatnbump]

Exhaust elbows can look "fine", and may even be "fine", but if they are of the type shown in the first photo in post #6 and if they are installed in that manner, you essentially have a "doomed to fail" setup. In essence it is only a matter of time, when, not if. With that setup under the "right" (wrong) circumstances, even having the boat lift operator lift the boat in a bow down angle (by mistake) could result in water entering the engine. When the interior (unseen) portion of the elbow corrodes through (even small holes) near the water injection point, water could enter the turbo (if equipped) or the exhaust manifold of the engine potentially resulting in severe engine damage.
Many on the forum probably already know about this, and/or have changed their setup to avoid this issue. However, my intent is to empower those who have not thought about this with the awareness and interest to investigate further to (potentially) save themselves from the headache and large expense involved should it happen to them. This "doomed to fail" design and setup should be considered (and changed as necessary) even if the elbow "looks and/or is" good.
Much more "technical" info is available for free on Seaboard Marine's (Tony Athens) website sbmar.com under Tony's tips and in the free forums.

Great Explanation. I had a set of 4LH STE in a Luhrs. I had nothing but trouble with the turbos and the elbows until I redesigned the exhaust system. One of the exhaust hoses was actually draining back to the turbo. If you go and research the exhaust questions on Boat Diesel a large majority are Mainship's and Luhrs. I am not picking on them I have had 2 Mainship's and a Luhrs .They seemed to have many problems.