Yanmar Maintenance issue: Mixing Elbow

[Capn Dan]

I recently noticed a crack in my Yanmar 3GM30F Mixing elbow. I removed the elbow and found that the downstream side of the mixing elbow was about 60-70 percent blocked. I used a chisel and knocked as much as I could free.

After I got back home with the elbow, I decided to cut it in half to see how bad the blockage was.

The attached pics tell the story.

This elbow is used on many Yanmars. Mine is a 3GM30F with only 1100 hours on it!

What you see is that the left half of the water inlet is 100 % blocked. The right side has a passage of only about ¼ inch.

What you are not seeing is the 60-70% blockage of the exhaust passage that I knocked out and what fell out during the cutting process.

I am not sure how you could clean one of these out, maybe take it to a radiator shop. It seems that this should be on your maintenance list for checking evey few years and a likely cause engine problems.

[Rakuflames]

Originally Posted by Capn Dan

I recently noticed a crack in my Yanmar 3GM30F Mixing elbow. I removed the elbow and found that the downstream side of the mixing elbow was about 60-70 percent blocked. I used a chisel and knocked as much as I could free.

After I got back home with the elbow, I decided to cut it in half to see how bad the blockage was.

The attached pics tell the story.

This elbow is used on many Yanmars. Mine is a 3GM30F with only 1100 hours on it!

What you see is that the left half of the water inlet is 100 % blocked. The right side has a passage of only about ¼ inch.

What you are not seeing is the 60-70% blockage of the exhaust passage that I knocked out and what fell out during the cutting process.

I am not sure how you could clean one of these out, maybe take it to a radiator shop. It seems that this should be on your maintenance list for checking evey few years and a likely cause engine problems.

When I had my new Yanmar put in I was told to expect to have to replace the mixing elbow about every five years. It is a part that gets "used up" and periodically has to be replaced. Cracks are common; pinholes are common; and clogging is common.

They're like windshield wipers on your car. They just don't last forever.

[djmarchand]

Exhaust elbows are a routine maintenance item on the 1/2/3GM Yanmar. 1000 hours is about normal for replacement.

David

[Liam Wald]

I have a Yanmar 3GM30F that was made in 2002. It does not have this type of elbow. What it has is an elbow that looks to be made of stainless steel and comes of the heat exchanger at 45%.
I am guessing that this is the next generation of elbow.
Does anyone have any experience or info about this?

[Capn Dan]

Liam,
My 3GM30F is about that age. I am guessing that your mixing elbow is an aftermarket however, I think that there were 2 versions of the 3GM30F..

Dan.

[Nor'Sea 27]

No aftermarket stuff involved probably.

Yanmar makes both versions of "elbows." The out and down (45 type) and the arch type. The idea is to get the elbow as high above the water line as possible. The 45 degree one works just fine where the motor is already relatively high - think power boats particularly planing boats. Sail and deep displacement type hulls need the elbow higher and that is the model shown in Capn Dan's excellent photos.

Charles

[Liam Wald]

Capn Dan,
Must be two different versions. The engine was new when I got it.
The way this thing is designed I can't see how it could ever clog.
I am familiar with the cast style like in the pictures above. They make a 180 degree turn.
The one I have is almost straight at 45 degrees like a chute and is either SS or monel.
How odd????
Hopefully someone will be able to fill me in about it.

[Liam Wald]

Originally Posted by Chas Erwin

No aftermarket stuff involved probably.

Yanmar makes both versions of "elbows." The out and down (45 type) and the arch type. The idea is to get the elbow as high above the water line as possible. The 45 degree one works just fine where the motor is already relatively high - think power boats particularly planing boats. Sail and deep displacement type hulls need the elbow higher and that is the model shown in Capn Dan's excellent photos.

Charles

Makes sense. My engine is mounted right at waterline. Does the 45degree version have the same clogging issues? Or is that a problem inherent to the tight turn version?

[Nor'Sea 27]

The (cast) arch model is far more pone to occlusions forming in the water passage- some seawater is always sitting in the water passage chamber. The cost is not very agreeable in my view either.

The 45 is easy to build - just about anyone could make one anywhere in the world - and the cost is quite agreeable even if factory.

Charles

[Capn Dan]

Charles,

It seems to me that the added height of the "U" cast elbow is not significant. Is there any reason not to switch to a 45 elbow? Any idea as to why Yanmar would make such a convoluted passage for the water?

Dan

[Nor'Sea 27]

Capn Dan

Take a look at EXHAUST INSTALLATION for a possibly helpful explanation.

Chas

[sailorchic34]

I think I'm going to try to use a bit of 1/4 plumbing snake wire in a drill and see how much crud comes out of mine..

BTW I has one of those small drum plumbing snakes. I cut the drain cleaner end off and use it for cleaning out through hulls, drains and as a wire / rope puller when adding new rope to the boom.

Thanks to the OP for the inside look

[captfolly]

great photos...!...our 3gm had not had any visible problems after 1800 hrs but decided to replace it during last summer's haulout. We used the stainless steel elbow from exhaustelbow.com... beautifully made, fit perfectly, some pics of our installation at: https://picasaweb.google.com/1027718...67170075479618 Only have about 70 hrs on it so far, but still looks like new...

fair winds,
George

[zeehag]

cleaning them in muriatic acid works well if it only a clogged section---the owner of the boat i cruised gom had done that -- got him over a year of use after cleaning...

[CaptainDana]

The reason for the convoluted waterpath is twofold. 1. 'Aims' the water down the exhaust on the muffler side so that hydrolock due to excessive cranking is delayed or obviated. 2. Spreads out the surface area where the metal comes in contact with the water allowing the water to cool the elbow. These pictures graphically demonstrate that the point where the exhaust-heated metal meets the relatively cool water stream is where carbon will build up.

GREAT POST!!