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Ss exhaust elbow to cast outlet iron manifold on Yanmar 3GM30F


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Is it good practice to use hi temp dressing as well as gasket?

Dissimilar metals so.......?

Elbow new 5yrs ago and looks to be pitted about half way thru inner, and can't remember what I did.

Whatever, worked. 

Current one relegated to spare and new heavy duty model going on.

 

 

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I just do not understand why people use s/s exhaust mixing elbows. Engines mostly cast steel.exhaust box(where exhaust attaches too)why not use stell all the way through. Do new motors come with s/s or steel?? My original lasted 15/16yrs and the galv is still in place 6yrs on and will prberly last another 10 yrs. I never put back on any lagging just made a heat shield that direct away from ply box back to motor.well vented box though.

Somehow need to isolate s/s from steel, s/s are thin walled as suffer heat and expansion. Corrosion statrs where rubber exhaust fits on to muffler box.For the expense do not see value for money.

Seems that with gas engines, cast iron elbows tend to last 5-7 years. On diesel, as you experienced much longer which may be due to the size of the water injection openings to control the greater heat created by the exhaust. When I had to replace 20 yr old cast elbows (2200 hrs) on my Perkins 6.354, I went with cupronickel fabricated by Marine Manifolds in Long Island, NY. Will probably outlast me smile.gif. With 2000 hrs I would certainly consider having a replacement aboard as insurance, as in my opinion, you are about at the end of the useful lifespan of your elbow.

https://www.cruisersforum.com/forums/f54/exhaust-mixing-elbow-life-52052.html

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Yanmar has a SS  OEM elbow for my motor so I presumed that was the way to go.

Never gave it a thought to use  a different material.

Anyway, committed to this heavy duty replacement as it can't go back but I see your logic.

Twice as thick a material as original. That about 200hrs/5yrs.

Dislike motoring.

Elbow.jpg

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The corrosion action between steel and SST is very small. A seal of some kind will be needed. Either Gasket, Silicon, or Exhaust cement. It is only when you jhave long lengths of SST that vibrations cause issues. A decent thickness well supported length will be fine.

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I have all of above  including the gasket.

We pulled it off straight after an hours motoring. It was colder than the head so don't think 

high temp applies. 

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I would ask a local engineer if you can grab a little bit of Nickle Antiseize. Or if they could coat the threads for you and put them in a plastic bag. It withstands very high temperatures and is the best for SST threads. Copper not so much. The nickle version is horrendously expensive, so you don't want to be buy a pottle of it just to do 4 threads.

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I spoke to an engineer who worked on oil rigs who said the same. They had stopped using the copper grease in favour of something else. If it’s expensive I tend to forget what it is and develope a mental block real quick. Haha.

If you are using a gasket do you use a dressing as well, like red rtv?

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