Gasket for Yanmar SS exhaust elbow

[Ken13559]

Hi Nick, I have now a U type elbow that has the form of a loop itself and also the exhaust hose has a tall loop near the exit at the transom.
So I think the engine will be protected with this tall loop and get a better performance with the SS elbow, at this moment the U type looks like is almost clogged with dirt and rust.

Between the mixing elbow and the transom high loop, you should have a water lock muffler. Water there can backwash to your engine. If your engine exhaust is not high enough this water will gets in. That's what happen to my friend's brand new 3 YM30 when he repowered. The engine comes with the straight SS mixing elbow. Now he will be installing the U type elbow whether he likes it or not. Every 9-12 montbs I would take my U type elbow out of decoking. Easy work.

 

[scorpio77]

Yes Ken youre right, there is the muffler installed.
With all the advice received from you and all the guys, Im starting to consider to just replace the existing U type ell with another of the same type, I dont want to get a flooded engine, anyway when I return to my boat I will measure the position of the exhaust outlet in reference to the water level, the Yanmar manual states that in order to have installed the straight ell, there must be a height of at least 6" from the water level to the exhaust outlet in the manifold and at least 10" from the center of the muffler to the exhaust outlet in the manifold,
Do you know if your friends engine is installed below this heights? Or why he got water in the engine

 

[Allan12210]

Here is the issue I see with the stainless steel part. The cast OEM part has an internal baffle that isolates the water injection from running back into the exhaust manifold and filling the rear cylinder. When could this happen? If the engine were cranked for an excessive amount of time because it wouldn't start, or if it was being cranked to bleed air from the fuel system. If the seacock wasn't closed in this case, that design looks like it will let the water run back into the engine because of no baffle and the injection point is too close to the exhaust manifold.

Regarding the thought that stainless is better...in this application the material is so thin I think it will erode sooner than a nice thick cast elbow. In
my case, my elbow did fail (albiet after many years) but not at either cast piece. It failed at the coupling that ties them together..the combo left and right hand threaded piece. It is made of stainless steel.

 

[Ken13559]

Jose, I don't the measurement of my friend's exhsust to muffler height. I guess if I draw a horizontal line fron the muffler centreline it'll be just about top of the prop flange coupling. His engine is more than 8deg angled fore-aft.

 

[scorpio77]

Found this pictures of an ell cut, theres the internal structure as you said http://www.ipyoa.com/photos/62-hayden/album?albumid=118 , thanks for the advice