Yanmar exhaust elbow

[Jared]

I know this has happened to other folks from reading the archives, but figured I would check to make sure I am reading the engine right. I started her this weekend and got no water out of the exhaust. I had rebuilt the waterpump earlier in the year, so I started upstream and disconnected the water hose where it fed into the exhaust elbow. When I fired up the engine, I got good waterflow (like a garden hose almost) out of the hose, but none was coming out of the exhaust. I then tried blowing into the connection of the water to exhaust elbow (figured it should be free), but could not get air into the elbow. I then hooked up my dinghy air pump thinking I could dislodge something with pressure - still could not get air to go through. I did not, however, disconnect the exaust hose first beacause I figured I didn't need to.Does this sound like a classic clogged exhaust elbow? I should be able to blow air through the water nipple if it was not clogged, right? I have no idea the last time it was changed - we have only owned the boat for 1 year. It had been belching a little black smoke on startup and starting sluggishly since we got her too.

 

[s sauer]

Exhaust Elbow Build Up

The Exhaust elbow on a 2GM20F is a casting with two parallel chambers, the larger of which is probably 2/3 to 3/4 of the available inside diameter which receives the exhaust flow from the exhaust manifold. The other smaller chamber receives the water flow from a bronze nipple about 1/2 to 5/8" diameter.Once the chambers start to get carboned up they will be difficult to clean, as the material is more like a hardened coke deposit.I used heavy duty comercial wire brushes on a variable speed drill and a cold chisel and hammer. Believe me, it's easier to buy and install a new one, but the connecting piece to the engine exhaust flange is a relatively thin stainless steel fitting with borh right and left hand threads, I paid a muffler shop to 'break' the two apart and I was able to clean them out because mine were not yet completely blocked.

 

[Bill O'Donovan]

Ditto

Sauer is absolutely right. Get a new one. Don't try to dismantle at the elbow.Instead undo 4 bolts at manifold.Be sure to get a new seal for the manifold.Run the engine hard to delay future buildup.

 

[John Nntz]

Engine Wear

For what it's worth, according to a Tech Rep at Cascade Engine Center, the Northwest Yanmar distributor, constricted mixing elbows account for the greatest wear on Yanmar engines, more so than any other single item.As a comment, if you manage to get the mixing elbow and coupler apart - and it'll probably be really difficult - when you reassemble them don't tighten them up any more than you have to. Try to err on the loose side as much as possible to make it easier to take apart the next time.When you reassemble it don't use regular antiseze compound on the threads, the kind that has a metalic component, it will just help to gall everyting up even harder for next time.

 

[Joseph Rheubeck]

Which Elbow?

Jared,Which exhaust outlet do you have? There two styles the "Elbow" looks like a piece of pipe bent 90 degrees with the water connectr on it and the other one, the "Riser" has a large "U" shaped casting with what looks like a pipe nipple attaching it to the flange bolted to the engine.If you have the "Elbow" style pull it off and attack with small wire wheels, screwdrivers etc.If you have the "Riser" call the parts department.

 

[Jared]

Elbow

Oh yeah, I forgot to say that it was the Yanmar 3GM30F, so that would be the U-shaped elbow. I am going to have a mechanic take a look at it and give me an opinion. I want the thing fixed, so I will just pay them to replace it since I hear that it involved blowtorches and things of that such to get these things off.