Mixing elbow exam

[Starrfish]

So my goal today is to replace the rubber exhaust hose that comes off my yanmar 1gm mixing elbow. It has a worn hole in it so the water leak is considerable. The repair manual says that while you have the old hose off it is recommended that the mixing elbow be removed and examined.
So I can take off the elbow and I do have a gasket to replace the old but I am not looking forward to doing it just to examine. I need some incentive from you guys .
Also, if and when I take the mixing elbow off, what am I looking for and what do I do without a new one to replace it?
Btw where do I get a mixing elbow for a yanmar 1gm?

 

[Sailm8]

I took mine off a few years ago. Turned out to not be a big deal. When you look into the elbow you will see caked up carbon that you can try to beat out with a chisel. Someone posted pictures of a cut away elbow so you can see the nooks and crannies and crap that gets collected. Try Mac Boring for a replacement part.

 

[Starrfish]

Thanks! I found one this morning for sale on eBay and am going to purchase it. Will try to remove any crude I find by bringing a chisel along.

 

[gray125]

How about about using a handheld inspection camera to look up into the elbow once the hose was off?

 

[markwbird]

mixing elbo exam

The reason for examining the mixing elbow when you get the chance is that they corrode from the inside out. A mixing elbow that looks perfectly fine from the outside may be near failure. You are checking for corrosion and to see if the metal is dangerously thin anywhere. The mixing elbow is one of those parts for which you should keep a spare on board if you are cruising

 

[Scott T-Bird]

I found it to be a very simple removal on my 1GM. There are only 3 easy-to-get-to bolts and it didn't take any prying at all. In fact, I removed it several times. Mine didn't have a gasket that I can remember, or maybe I just left the old one in place ... I never had anything leak from the connection face, although I suspect that some will say that exhaust gas will leak there, leading to problems.

You will probably find that the black surfaces on the inside will not change appreciably no matter how you try to clean it. I scrubbed with wire brushes, soaked in hot water, soaked in solvent and could not detect any difference before or after. The only thing I discovered was that my fingers would get smudgy black from the cleaning effort while the interior surfaces of the mixing elbow didn't change in any way. I found no sign of any metal corrosion whatsoever in an engine that is 30 years old by now.

Personally, I never found the mixing elbow to be the source of any problem, but what do I know? If you want a clean, shiny-metal mixing elbow you may as well buy a new one (from Mack Boring), I think. That is what I plan to do this winter when I finally get around to rebuilding my 1GM which is currently in the basement.

 

[Ralph Johnstone]

Not Saying This Will Give You Incentive ......

I need some incentive from you guys .

................. but it may give you some sleepless nights.

This is the result of running the engine correctly ........... 85% loaded when running. Don't want to know what would happen if it were not run hard. The elbow had about 400 running hours.

I suspect it may have something to do with the hot engine compartment (150 F) and lower density air. Engine comaprtment is like a Nike shoe box. I recently installed a cooling fan (now 90 F) so I'll be keeping an eye on carbon buildup.

 

[Scott T-Bird]

1GM

Wow, what a difference! I suppose running in salt water is an issue. I also wonder if the U-shaped elbow makes a difference. The 1GM has a 80 degree bend, not 180 degree like you show.

My new 2YM15 has the U-shaped elbow similar to your cut-away.

Hear is what I typically found after removing the elbow

 

[shemandr]

August 2014 issue of Sail has a short article with pics on this subject.

 

[Ralph Johnstone]

Don't Ever .........................

Wow, what a difference! I suppose running in salt water is an issue.

....................... put salt water in those things, as you can see the results.

I guess it's a trade off. Corroded and plugged mixing elbows are the price you pay for a beautiful coast line.

 

[Johnb]

Definitely worth checking the mixing elbow. When mine went a big chunk just popped off. That set off the fire and CO2 detectors and exhaust fumes and sea water were just pouring into the cabin area, effectively requiring the engine to be out of service forthwith.

Be prepared for the possibility of other issues. I had to have the exhaust manifold to mixing elbow flange surface re machined.

 

[Dave602]

In my opinion if you plan on keeping the boat and the elbow is original equipment I would replace it vs cleaning. If it is clogged you are just putting off the inevitable. I replaced mine and never looked back. It looked shiny and new on the outside and i couldn't get my little finger around the bend on the inside. Good to go for many years now.

 

[Starrfish]

What is this?

This part looks to be a personal manufactured one. It is between my mixing elbow and stern exhaust port. Anybody know what it is ?

 

[Ted]

This part looks to be a personal manufactured one. It is between my mixing elbow and stern exhaust port. Anybody know what it is ?

It's a waterlift muffler.

 

[Scott T-Bird]

Waterlift and anti-siphon

It looks like you are possibly going to re-vamp your exhaust system. Check out the Vetus waterlift mufflers. I had two components that went with the old 1GM installation, and I basically duplicated them for my new engine, except I increased the diameter.

Photos show the old water-lift & new installation with water-lift and anti-siphon which is mounted at the stern just above the discharge.

 

[Granfalloon]

Re: Waterlift and anti-siphon

Running the engine at 85% is good. Another is to run the engine at max RPM for a few minutes after the engine is warmed up. I do this on returning rom a daysail. I look at the exhaust for good flow and smoke.
You can chip out the carbon build up and you could also let it soak in some muriatic acid (in open air - toxic fumes), rinse and chisel again.

I think the best way to go however, is to replace it and use the rehab one as a spare.

 

[NYSail]

In my opinion, replacing is a small price to pay. If it fails internally you might not know until the engine quits working due to water flowing the wrong way. Also check out centrex for water lifts...... Great fiberglass units and all sorts of fittings as well. Good luck!

 

[Nereussailor]

Your exhaust elbow is essentially the same as the one on my 2GM. It is a 80 degree pipe with an other pipe inside of it. The flange has 3 bolts that hold it to the head. Once removed, you should be able to look in the end of it with a flashlight and see if there are any deposits in between the tubes. If there are, you can get between the tubes with a piece of wire. Mine was really clean for being 31 years old but I run it almost full throttle for at least 20 minutes before docking. Try pressing the tubes of the elbow together with your fingers., if there is any real movement, replace it. I just removed mine and cleaned it while it was out. As you can see from the pictures, it's a little pitted on the outside from salt water, but it's solid. The other place you want to check is the area where the inside tube meets the outside tube at the base of the flange. This is where you might find corrosion. The top left bolt in the head, as you're facing the elbow, was broken, so I had to drill, re-tap the head and put an EZ-lok in. Not a fun job, but it was leaking exhaust and the carbon was on everything.

 

[Starrfish]

Thanks. Very helpful all. I removed and there was no build up and so replaced with new gasket and cancelled order of new one to replace. Never a problem but had never been checked.