I Have A Hunter 340 97' We were just on our way to st Augustine to get our boat fixed from the hurricanes when i noticed black smoke and sud coming out of the exhaust. The engine seemed to be running ok in idle but with a load it started to smoke. We made it back to the dock.I checked the fuel filters they were ok.Had a Diver clean the prop and check the bottom that was ok. all thats left is the fuel pump or the injectors?? We have a yanmar 27hp engine. Any Ideas??? Captain Wolf
Yanmar Diesel
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ELBOW!
Wolf: Check out the mixing elbow. Be sure that you have a new gasket just in case that is not the problem. It is not very difficult to do, but it is a little time consuming. You will need a large bench vice and a pipe wrench with a breaker bar, or a couple of large pipe wrenches. A torch is also a good addition to getting the manifold and the elbow apart. The threads on the coupling between the manifold and the elbow are opposite threads (one is right and the other is left). If you check out Photo Forum, there is a post there for the procedure.
Wolf: Check out the mixing elbow. Be sure that you have a new gasket just in case that is not the problem. It is not very difficult to do, but it is a little time consuming. You will need a large bench vice and a pipe wrench with a breaker bar, or a couple of large pipe wrenches. A torch is also a good addition to getting the manifold and the elbow apart. The threads on the coupling between the manifold and the elbow are opposite threads (one is right and the other is left). If you check out Photo Forum, there is a post there for the procedure.
I do not know for sure about the 27hp
but my 35hp yanmar elbow is easy to remove. Just loosen the 4 bolts a little, give her a twist back and forth to loosen the gasket, remove the bolts and take off the elbow. You do not even have to take off the hose. If you want to remove the hose, do that first then the 4 bolts. Steve, if the elbow is not cracked or otherwise ruined, why put yourself through all the pipe wrench drama for nothing? FYI - my Home Depot model is still going strong!
but my 35hp yanmar elbow is easy to remove. Just loosen the 4 bolts a little, give her a twist back and forth to loosen the gasket, remove the bolts and take off the elbow. You do not even have to take off the hose. If you want to remove the hose, do that first then the 4 bolts. Steve, if the elbow is not cracked or otherwise ruined, why put yourself through all the pipe wrench drama for nothing? FYI - my Home Depot model is still going strong!
The prop was the likely problem
Did you run a sea trial after the prop cleaning? My Yanmar mechanic insists that a fouled prop is the main cause of black smoke with no other symptoms. I had a similar problem with my 2000 340 when we bought it last month. The prop was badly fouled and the engine belched smoked smoke and put soot in the prop wash. The mechanic tested the injectors and ran a comperssion test for my peace of mind. Everything tested good and once the prop was cleaned she ran smooth and clean. If you have the time, it is never a bad idea to check your mixing elbow but try the engine with a clean prop first.
Did you run a sea trial after the prop cleaning? My Yanmar mechanic insists that a fouled prop is the main cause of black smoke with no other symptoms. I had a similar problem with my 2000 340 when we bought it last month. The prop was badly fouled and the engine belched smoked smoke and put soot in the prop wash. The mechanic tested the injectors and ran a comperssion test for my peace of mind. Everything tested good and once the prop was cleaned she ran smooth and clean. If you have the time, it is never a bad idea to check your mixing elbow but try the engine with a clean prop first.
In my two decades of sailing
the smoking engine has always been a clogged elbow with one possible exception when I had a giant clump of seaweed in tow. Come to think of it, I do not think that the engine smoked then too much. Just slowed the boat down. It is easier to check the elbow than the prop where I live so I would still advise doing that first. The mechanics I hired once cost me over $500 to check the injectors and pump and never did figure out the elbow problem. My theory is that mechanics think about things in the way they were taught (ie truck engines) and their educated thinking is not always the best way to go on a boat.
the smoking engine has always been a clogged elbow with one possible exception when I had a giant clump of seaweed in tow. Come to think of it, I do not think that the engine smoked then too much. Just slowed the boat down. It is easier to check the elbow than the prop where I live so I would still advise doing that first. The mechanics I hired once cost me over $500 to check the injectors and pump and never did figure out the elbow problem. My theory is that mechanics think about things in the way they were taught (ie truck engines) and their educated thinking is not always the best way to go on a boat.
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