Exhaust Mixing Elbow Life

[Captain Bill]

I had both of my elbows fail at about 900 hours, Yanmar told me the standard life was 500 hours. They failed at the weld on the flange from corrosion. I tried having them welded but it only lasted about 25 hours. At about $300 a piece I was not happy about replacing them. Then I found out that on occasion some Yanmar dealers have "Take offs" available. Yanmar offers several optional exhaust elbows and when a customer wants an optional one, the dealer removes the stock elbow. The elbows have never been used but because they had been previously installed the dealer is not allowed to sell them as new. I bought 4 of them for $300 and now have a set of spares for the next time they fail.

[David M]

I think it's nuts that engine manufactures are selling a part that is expensive, a PITA to change out and has such a short lifespan. That sure makes things more profitable for them and their dealers.

[sailorboy1]

So far on the thread I've found that my 2000 hours mixing elbow sounds unsual high. Guess all the blogs I've read about the mixing elbow problems are true.

[redhead78]

I paid a little extra for a high rise stainless elbow with my new engine, I felt it would last longest, of the other materials offered. I guess I will find out.....Red

[TopHat]

If the mixing elbow is of a simple design, its totally possible for an amateur to fabricate a replacement, Ive just been through the process
tophatyachts.org • View topic - Inboard Diesel Exhaust

On reflection, I should of made it from Stainless steel, but the mild steel & Duragal parts were readily available.
Id guess the mixing elbow that failed (choked up with rust, inside, from the sea water) was at least 15yrs old, but used very rarely.
cheers

[barnakiel]

Approx 10 years on our Volvo (cast iron item). If it corrodes at the lower end it can be fixed with epoxy until a new one is available (we did). But if it corrodes at the upper end it can just break off unexpectedly. Therefore dismount yours and check it.

barnie

[Captain Bill]

Originally Posted by TopHat

If the mixing elbow is of a simple design, its totally possible for an amateur to fabricate a replacement, Ive just been through the process
tophatyachts.org • View topic - Inboard Diesel Exhaust

On reflection, I should of made it from Stainless steel, but the mild steel & Duragal parts were readily available.
Id guess the mixing elbow that failed (choked up with rust, inside, from the sea water) was at least 15yrs old, but used very rarely.
cheers

I wouldn't worry too much about it not being made of stainless. The machine shop guy who welded mine told me there's no such thing as stainless welding rod, so while the body may be stainless the welds were not. He also noted tha stainless elbows were thin walled and that meant thin welds, so stainless elbows didn't last very long. They tended to corrode through at the welds. I'm not much of a metallurgist, but that makes some sense to me. Note that mine failed at a bit over 900 hours, but they had 525 hours on them when I bought the boat. What I don't know is if the PO had already replaced them once.

[nickc]

Originally Posted by redhead78

I paid a little extra for a high rise stainless elbow with my new engine, I felt it would last longest, of the other materials offered. I guess I will find out.....Red

High Redhead 78,
Is this for a Yamar and if so do you have any way I can identify it; ie link, part number or picture. Tks Nick

[Laidback]

Originally Posted by Captain Bill

I wouldn't worry too much about it not being made of stainless. The machine shop guy who welded mine told me there's no such thing as stainless welding rod, so while the body may be stainless the welds were not.

The Machine Shop guy may need to widen his horizons. I have stainless electrodes 316 and 304 for arc welding. Here is a little basic info on the subject :- Procedures: Stainless Steel Welding

[sailorboy1]

Originally Posted by Captain Bill

.... The machine shop guy who welded mine told me there's no such thing as stainless welding rod, so while the body may be stainless the welds were not. .............

I hope you have a spare before heading out as your elbows are going to fail!

[barnakiel]

Yep. If your elbow is that old and already corroded then it is wise to have a spare.

But then, is it not wise to replace the thing BEFORE the big trip?

barnie

[doug86]

Originally Posted by Don Lucas

Should a mixing elbow be considered an important spare part to stock on the boat for a long trip?

I would answer yes, definitely to that question. As you can tell from the previous posts, the life of an exhaust elbow is hard to predict. (I replaced a working elbow last year on my FL120 as it had 2400hrs on it. Once the old one was off, I found a spot at the bottom that was so corroded that my fingernail pushed a small hole through)

You say "a long trip". If the mixing elbow does fail, it is very hard to jury rig a decent repair, and oh so easy to just bolt on the new one. It is the kind of repair that you could do even offshore, or in a remote anchorage. Otherwise, you are waiting for a part from god knows where.

A mixing elbow should be considered an important spare to carry on a long trip.

[Captain Bill]

Originally Posted by Don Lucas

I hope you have a spare before heading out as your elbows are going to fail!

As Noted on a earlier post on this thread, they lasted only about 25 hours after welding at which time I replaced them with new ones and I keep a spare set on board.

Laid Back,
That's interesting information, I will keep that in mind next time I need something welded.

[donradcliffe]

If you bring a spare, the original will never fail--Zen and the Diesel Mechanic.

My 4108 aluminum elbow corroded through at about 2000 hrs--epoxy got it going until a new one was shipped in, which lasted over 2000 hrs.

Stainless is not the material of choice--the temperature fluctuations/gradients and salt environment make for intergranular stress corrosion cracking. Ask any nuclear power plant designer.

[svcambria]

Originally Posted by doug86

I would answer yes, definitely to that question. As you can tell from the previous posts, the life of an exhaust elbow is hard to predict. (I replaced a working elbow last year on my FL120 as it had 2400hrs on it. Once the old one was off, I found a spot at the bottom that was so corroded that my fingernail pushed a small hole through)

You say "a long trip". If the mixing elbow does fail, it is very hard to jury rig a decent repair, and oh so easy to just bolt on the new one. It is the kind of repair that you could do even offshore, or in a remote anchorage. Otherwise, you are waiting for a part from god knows where.

A mixing elbow should be considered an important spare to carry on a long trip.

My whole enthusiastic agreement with Doug. Mine just failed in Guaymas, Mexico, unexpectedly; a bent-elbow type for a Yanmar 4JH3, rusted out at the bottom but fairly free of carbon. Looked great from what one could see when it was in place. Ten years and 1150 hours on it. With a spare I was able to change it out on the spot (unpleasant but possible); without a spare I would be waiting for a new one to be shipped to Arizona where someone else would be bringing it south - sometime in the indefinite future.

Michael