Yanmar manual mixing elbow maintenance
- Thread starter SEMPERAVANTI41
- Start date
That makes sense but I don't think my motor is that low. It rests behind the companionway stairs.
I think if it has the U type setup than it must be needed,me I would not want to take the chance of water backing up into the engine.
Nick
Nick
A good reason to NOT buy a SS knock off: I took my original 2GM20F elbow+coupler+riser to the yanmar parts center and THEY took the old unit back to their shop and THEY removed the old riser and replaced it with the new. They also said to bring it in every 3 years and the'll clean it for free.
BTW: Disconnecting the exhaust hose was tricky, but this is how I did it.
1) Remove the SS hose clamp
2) Disconnect the 4 elbow bolts to the exhaust manifold and the injection hose
3) Using a heat gun, heat up the exhaust hose around the top
4) Using WD40, spray around the hose
5) After a while, using a small flat screwdriver, carefully drive it in about 1/2 inch all around the hose
Reheat the hose. Spray more WD40, let it pool around the top and let it seep in. Drive the small screwdriver in deeper. Repeat. After a while, using the elbow+coupler+riser as leverage, try to twist the hose. After a while, it will twist and separating the hose and unit will be possible.. Then take the whole unit to the dealer! That's it... Worked for me!
BTW: Disconnecting the exhaust hose was tricky, but this is how I did it.
1) Remove the SS hose clamp
2) Disconnect the 4 elbow bolts to the exhaust manifold and the injection hose
3) Using a heat gun, heat up the exhaust hose around the top
4) Using WD40, spray around the hose
5) After a while, using a small flat screwdriver, carefully drive it in about 1/2 inch all around the hose
Reheat the hose. Spray more WD40, let it pool around the top and let it seep in. Drive the small screwdriver in deeper. Repeat. After a while, using the elbow+coupler+riser as leverage, try to twist the hose. After a while, it will twist and separating the hose and unit will be possible.. Then take the whole unit to the dealer! That's it... Worked for me!
Justin, this pic illustrates how the design of the stock Yanmar GM mixing elbow directs the flow of raw water down and away from the exhaust manifold. It also shows how the buildup of crud restricts the flow of water. The other thing it does is elevates the mixer high enough to prevent back flow of water into the exhaust manifold. If water does get into the manifold and any of the exhaust valves are open, then water gets into the cylinder.... not good.
I'm not saying that your ss would not work. It looks like there would be less restriction for water and exhaust flow and less opportunities for corrosion. Just make sure your engines exhaust pipe is routed so there is no chance of ocean water backing into the mixer when the engine of off. And avoid trying to start the engine for a long period of time with the raw water seacock open.
I'm not saying that your ss would not work. It looks like there would be less restriction for water and exhaust flow and less opportunities for corrosion. Just make sure your engines exhaust pipe is routed so there is no chance of ocean water backing into the mixer when the engine of off. And avoid trying to start the engine for a long period of time with the raw water seacock open.
Looking at the cutaway elbow, I am surprised by the restriction in the exhaust. It looks like the effective diameter of the exhaust is halved at the threaded fitting,then halved again just before the water inlet into the exhaust stream. Mathematically that would initially cut the cross sectional area by a factor of 4 and then a factor of 4 again. That seems to me like it would strangle the engine. Apparently Yanmar doesn't consider that to be a problem.
The is a great cutaway picture! It definitely shows how restrictive they get by design and by lack of regular maintenance. We don't have anyone around here with the customer service mz4wheeler has. I'm not convinced that with the exhaust thruhull right at the waterline that I need the extra 4" lift that the U-type provides is necessary. Seem like plenty of rise with the straight version to allow the water to drain properly and not find a way back into the engine thru the exhaust. I will try to find some history on the Yanmar/Hunter setup.
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Interesting article on the U-shaped elbow. How far up is enough to determine you do or do not need it vs the straight version. I don't think we have a waterlock muffler...
http://www.sailmagazine.com/diy/maintaining-your-diesel-exhaust/
I think it's more likely that a failed U-type would send water back into the head before a straight design would.
http://www.sailmagazine.com/diy/maintaining-your-diesel-exhaust/
I think it's more likely that a failed U-type would send water back into the head before a straight design would.