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Old 05-11-2018, 04:14   #1
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Yanmar 3GM30F mixing elbow and exhaust manifold question

I’m about to replace my mixing elbow with a new SS one and I have a few doubts. I’d appreciate some advice.

Should I also remove the exhaust manifold for cleaning? I’m assuming if there is carbon buildup in the elbow, there must be some in the manifold as well. Any ideas on how to best clean the manifold? Anything I should know before I remove it? Do I have to fit a new gasket if I remove it?

Thanks!
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Old 05-11-2018, 04:40   #2
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

With the elbo off, you'll be able to inspect the manifold, and make an informed decision.

See also ➥ Yanmar 2GM20F mixing elbow replacement
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Old 05-11-2018, 04:42   #3
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

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Originally Posted by GordMay View Post
With the elbo off, you'll be able to inspect the manifold, and make an informed decision.

See also ➥ Yanmar 2GM20F mixing elbow replacement
Thanks Gordon! I'll try that, but I don't think I'll be able to really see very much inside the manifold from just the opening for the elbow.
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Old 05-11-2018, 06:43   #4
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

I cleaned the exhaust manifold on my 3 gm raw water cooled last year when I changed to
SS elbow. I could see some carbon build up when I removed the elbow and was getting
a slight build up on transom near exhaust.
Cleaned manifold with a muriatic acid soak and brush but have to neutralize with baking soda after.
Must replace the 2 gaskets (1 between head and EM and 1 between EM and water jacket cover, if that's what its called?) had to remove secondary fuel filter and fuel lines.
And have to torque bolts back as speced.
I also flush the motor with Rydlyme every few years, have to remove thermostat and replace impeller after. Full info on line, Mainesail on sailnet or here on CF.
Helps keep motor happy.
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Old 05-11-2018, 07:08   #5
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

i've seen the SS mixing elbows on Ebay. they look very nice
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Old 05-11-2018, 09:00   #6
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

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Originally Posted by Copacabana View Post
Thanks Gordon! I'll try that, but I don't think I'll be able to really see very much inside the manifold from just the opening for the elbow.

No, but you haven't stated any other factors that would justify the bother. High engine hours, long idle times and a few others come to mind, but I don't think it's a bad idea to clean it out if you can get it off without breaking the mounting studs and replacing the gasket, if suspect. When I replace some element of a sub-system that is in the middle of said system, such as the mixing elbow is in relation to the exhaust ports of the diesel to where the smoke and water exit the hull, I like to think of it as an opportunity to evaluate the entirety of that sub-system, meaning hose condition, hose clamp condition, state of the water lift muffler, etc. I would recommend Permatex or other anti-seize, anti-corrosion measures on the mounting studs for the flange or the manifold to faciliate future repair or examination.
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Old 05-11-2018, 09:02   #7
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

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Originally Posted by hugosalt View Post
I cleaned the exhaust manifold on my 3 gm raw water cooled last year when I changed to
SS elbow. I could see some carbon build up when I removed the elbow and was getting
a slight build up on transom near exhaust.
Cleaned manifold with a muriatic acid soak and brush but have to neutralize with baking soda after.
Must replace the 2 gaskets (1 between head and EM and 1 between EM and water jacket cover, if that's what its called?) had to remove secondary fuel filter and fuel lines.
And have to torque bolts back as speced.
I also flush the motor with Rydlyme every few years, have to remove thermostat and replace impeller after. Full info on line, Mainesail on sailnet or here on CF.
Helps keep motor happy.

Indeed. Pretty much this. Muriatic acid is bastard juice, but does the trick if you are careful. I've used it, carefully, on toilets. Wear full protective gear and gloves, however.
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Old 05-11-2018, 09:09   #8
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

yes. You will need a new gasket
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Old 05-11-2018, 09:41   #9
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

On our 3GM30F equipped Hunter Legend it was easiest to remove elbow and manifold as one piece and reinstall with a new elbow. The murietic acid cleaned up the used elbow and now it's a spare. The manifold cleaned up nicely and was reused. A 150 hrs later it's still ok but the paint on the manifold peeled. New gaskets were cheap insurance.
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Old 05-11-2018, 09:46   #10
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

I just rebuilt my 3 GM 30F after a lot of hours. New pistons, new injectors, rebuilt the injector pump, had the head redone.



I also took apart the tubing bundle in the exhaust manifold and cleaned it. I have had to replace the exhaust elbow at least 3 or 4 times in the life of the engine.



the tubes inside the manifold were very clean and probably didn't need to be taken apart it was so clean.



Your mileage may vary,


Good luck!


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Old 05-11-2018, 17:00   #11
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

When I removed the mixing elbow on my Perkins 3 cylinder I found considerable coke on the exhaust manifold outlet, probably due to the mixing elbow corroding through allowing raw water to get right at the exhaust manifold interface. I had a radiator repair place remove the coke and they said there was another leak in the manifold itself between the antifreeze coolant chamber and the exhaust path. No possibility to repair it, cast aluminum is nasty to weld, and the leak was inside the manifold. Oh yes, I had been adding more coolant than in the past.
The message here is to check the manifold integrity when you have the mixing elbow off. It is not hard to remove the manifold once the elbow is detached. It also gives you a chance to inspect and clean the water/ water heat exchanger. I taped over all the coolant ports on the manifold and then filled the manifold with water up to the filler cap and looked for leaks into the exhaust path.
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Old 05-11-2018, 20:07   #12
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

To change the mixing elbow had to pull the exhaust pipe at the heat exchanger. The elbow was so thoroughly stuck on the exhaust pipe couldn't get leverage to turn it in place. Had to call a diesel mechanic with a large vise in his truck to hold the exhaust pipe while hauling on the elbow with a large pipe wrench and cheater bar.
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Old 06-11-2018, 01:09   #13
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

Thanks for the advice everyone. I've decided to pull the manifold and have it cleaned at a local shop along with the heat exchanger. I might as well check everything over since I've got the tools out...

I just hope the bolts on the maifold don't give me a hard time.
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Old 06-11-2018, 13:02   #14
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

i was going to say .. yanmar says don't try to twist the elbow off while manifold is still bolted to the motor. let us know how it goes with the corroded bolt removal.


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Old 06-11-2018, 13:07   #15
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Re: Yanmar 3GM30F mixing elbow and exhaust manifold question

Gonesail, I have the other type of elbow on my engine- the one with the gentle curve. I was thinking of removing the manifold with the elbow attached and dealing with it on the bench. I'm hoping the manifold bolts won't give me a hard time... I'll let you know how it goes.
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