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  Topic Review (Newest First)
12-06-2013 02:31 PM
Yanmar Mix Elbow

I started to see a lot of black/brown soot when revving by motor so it determined it could be 1 or 2 things:
  1. Injectors were becoming clogged and therefore needed to be pulled and cleaned or
  2. Exhaust elbow was clogged with soot.

At first I was not looking forward to pull the whole exhaust portion of the motor off, but it is super simple and can be done in about 15 min if easy access. Disconnect the cooling water hose from the mixing elbow and then disconnect the whole piece of the exhaust manifold (mixing and exhaust elbows) from the motor by removing the 4 bolts.

I took mine home, separated the exhaust elbow from the mixing elbow, removed as much scale as I could with flat head screw driver, then soaked the both pieces overnight in vinegar.

Thoroughly rinsed and check flow through each with a stream of water. Reassembled, put on a new exhaust gasket and then put everything back together.

Fired up motor and black/brown smoke was gone.

My elbow is original to the motor, 1992, but my motor only has 700 h.
12-06-2013 10:42 AM
Re: Clogged Yanmar mixing elbow?

now thats some smart thinking, fix your current stuff to act as working spares...kind of a sailors motto
12-06-2013 08:39 AM
Re: Clogged Yanmar mixing elbow?

Thanks for the tips everyone. I still plan on replacing the elbow because the welds look a little rusty and it is probably time anyway (2,500 hours). I'll clean up the old elbow and put it in the "spares" kit.
12-05-2013 12:35 PM
Re: Clogged Yanmar mixing elbow?

yup shops "boil them" if its cheap to do won there like here I would do that...however you can do the rest yourself using vinegar...
12-05-2013 12:29 PM
Re: Clogged Yanmar mixing elbow?

Seems cleaning would be a lot cheaper than replacing. I would pull it and if you see any carbon on it, take to a radiator shop and ask them to "boil it out." (not sure what the Portuguese term would be as they don't really boil it) They generally have baths of really strong chemicals that they can dip it into and it will clean it to bare metal. You should be good to go for several more years after that.
12-05-2013 12:25 PM
Re: Clogged Yanmar mixing elbow?

before removing put the inlet in a vinegar bucket...start engine and completely suck all the vinegar till it starts coming out...

let sit for at least 24 hours...sometimes up to 48

then flush with distilled water(cold)

if this DOESNT help you must dismantle and manually clean

this shoud be done as regular maintenance and you save a lot of money versus buying industrial engine "cleaners"

I did this on my last engine an atomic 4 and the difference in max loaded rpm was very noticeable

power loss and parasitic loads can come from many sources on an engine, fuel, air, cooling system, belt chafe...etc...
12-05-2013 12:21 PM
Re: Clogged Yanmar mixing elbow?

I had it in my old boat. Yanmar recommends changing it out every 250 hours or get it cleaned at a radiator shop. The mixing elbow in this model is very prone to carbon blockage. Also the water inlet to the mixing elbow is famous for getting clogged first.
One way to know is the exhaust smoke starts to get white at running speeds.
12-05-2013 12:19 PM
Re: Clogged Yanmar mixing elbow?

soak in vinegar and do some vingear flushes of the intake and let it sit for a while

does wonders

edit I had the 2gmf, I think the elbows are the same...not sure though
12-05-2013 12:08 PM
Re: Clogged Yanmar mixing elbow?

I have the U shaped elbow with a straight pipe for the water inlet. The inlet was completely blocked.
12-05-2013 10:38 AM
Re: Clogged Yanmar mixing elbow?

Thanks Ron. I'm rather hoping to find the elbow clogged with carbon. Then I'll know I've found the problem. I'll find out when it's off. I know the U-shaped Yanmar elbow is prone to buildup, but the one I have just seems to have such a straight run that I can't see how it gets clogged. If anyone has the same elbow, I'd love to hear about clogging.
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