While returning home from a day of sailing we were under power and the engine starter to sound strange. It would not rev above 1500 rpm. I had a local Yanmar tech look at it and the more he tried to bleed the system the worse it got. Another tech has worked on it and the engine will start on any 2 of the three cylinders (the third is de-compressed). Black smoke comes out the air intake and the motor revs only to 800 rpm. When we engage the third cylinder the engine stops. We have tested the fuel and filters, they are fine. There is no air lock. We are getting both water and raw fuel out the stern. Any suggestions?
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Bryan C.
Breathing problem?
Sounds like you may have a coked up exhaust system. Carbon can build up (the mixing elbow is particularly a susceptible place) and restrict the amount of air flow. No air flow, she no go so good. Check the archives.
Sounds like you may have a coked up exhaust system. Carbon can build up (the mixing elbow is particularly a susceptible place) and restrict the amount of air flow. No air flow, she no go so good. Check the archives.
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John K Kudera
Try The Exhaust elbow
I had a similar problem this spring, that is what I found, same symptoms as yours, I replaced the elbow, no more problem. Please post the cause when you find it, Thanks, and good luck!
I had a similar problem this spring, that is what I found, same symptoms as yours, I replaced the elbow, no more problem. Please post the cause when you find it, Thanks, and good luck!
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Bryan C.
Right
Right, I meant the exhaust elbow. A U shaped thing near the engine exhaust port. There is a picture post by Steve Dion on changing these things in the archives.
Right, I meant the exhaust elbow. A U shaped thing near the engine exhaust port. There is a picture post by Steve Dion on changing these things in the archives.
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Sean Mullaly
You were right
You guy's were right. The mixing elbow was cloged with rust and soot. I waited too long to post my first message and I went through 3 desiel machanics. The third guy after testing the compression shook his head and then said "We'll have to take the engine out of the boat and take to the shop". "I don't thick so!!!!!". I called the first guy back and asked if that sounded reasonable. He said we should test the injectors and fuel pump first. He had never seen a fresh water cooled Yanmar clog at the mixing elbow. I called him with your collective advise and he said that is what he was going to check next. And you guys were right. The engine sounds better than ever. Thanks again.
You guy's were right. The mixing elbow was cloged with rust and soot. I waited too long to post my first message and I went through 3 desiel machanics. The third guy after testing the compression shook his head and then said "We'll have to take the engine out of the boat and take to the shop". "I don't thick so!!!!!". I called the first guy back and asked if that sounded reasonable. He said we should test the injectors and fuel pump first. He had never seen a fresh water cooled Yanmar clog at the mixing elbow. I called him with your collective advise and he said that is what he was going to check next. And you guys were right. The engine sounds better than ever. Thanks again.
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Bryan C.
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David
Mixing Elbow
Sean, Did you have to replace the mixing elbow or were you able to clean it out and reuse it?
Sean, Did you have to replace the mixing elbow or were you able to clean it out and reuse it?
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Bryan C.
Don't think they are expensive.
I haven't priced it, but others (if I am recalling correctly) quoted prices for new elbows in the $50-75 range. For that price, best to get a new one; not only do the fill with soot, the seawater corrodes them over a period of time.
I haven't priced it, but others (if I am recalling correctly) quoted prices for new elbows in the $50-75 range. For that price, best to get a new one; not only do the fill with soot, the seawater corrodes them over a period of time.
Not too expensive...
I paid about $85-90 for mine last year plus the gasket. Did not get the coupler or the exhaust manifold for that price. Remember if you do this yourself, the elbow and the manifold can be almost impossible to get apart. We needed a torch and a large pipe wrench to break them apart. Be sure to use "never-sieze" on the treads when re-assembling. And Brian is correct, if you have been using it in salt water (especially) they can become very corroded. I'd order a new one and see if you can clean up the old one and save it as a spare. If you take the old one to a radiator shop or a garage and have them soak it in the cleaning solutions they may be able to clean it up.
I paid about $85-90 for mine last year plus the gasket. Did not get the coupler or the exhaust manifold for that price. Remember if you do this yourself, the elbow and the manifold can be almost impossible to get apart. We needed a torch and a large pipe wrench to break them apart. Be sure to use "never-sieze" on the treads when re-assembling. And Brian is correct, if you have been using it in salt water (especially) they can become very corroded. I'd order a new one and see if you can clean up the old one and save it as a spare. If you take the old one to a radiator shop or a garage and have them soak it in the cleaning solutions they may be able to clean it up.
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