I have a 1997 Hunter 27 with a Yanmar SB8. The problem is that under a load the engine puts out black smoke. I have installed new fuel injector new fuel pump new fuel filter new head new valves new cylinder liner new piston new rings adjusted he valves to 0.2mm changed the oil put in fresh fuel Is there something else I can do or talk to that will help to stop this smoke problem
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Rich
Air filter
Check if the air filter is dirty. Some Yanmar filters only need to be washed in warm soapy water, then rinsed.
Check if the air filter is dirty. Some Yanmar filters only need to be washed in warm soapy water, then rinsed.
Too much fuel!
Tim: Black smoke is usually better than blue and white. This means that you are overloaded. Now that you have done ALL of this engine work, I think you need to check your prop. Are you running the stock prop or the same one as before you started these repairs? The prop may be fouled too. Once you know that the prop is clean and properly pitched you can go back to look for engine problems. I must assume that you have checked your air intake too. No blockage and the air filter is clean. PS: Did you rebuild the engine for a specific problem?
Tim: Black smoke is usually better than blue and white. This means that you are overloaded. Now that you have done ALL of this engine work, I think you need to check your prop. Are you running the stock prop or the same one as before you started these repairs? The prop may be fouled too. Once you know that the prop is clean and properly pitched you can go back to look for engine problems. I must assume that you have checked your air intake too. No blockage and the air filter is clean. PS: Did you rebuild the engine for a specific problem?
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Paul Akers
Overload
I had this discussion with a good mechanic last week. It's possible that your engine is overloaded while operating. In other words, there is extra drag somewhere on your engine that causes it to create backpressure and overload the engine. Some causes are as follows: Barnacles or growth on the prop/shaft that causes it to overwork. Wrong prop for the engine (it could be overpropped), meaning that there is too much bite as the prop spins and would require reducing the pitch of the prop. Your mixing elbow could be coking up and causing back pressure. This is what happened to me. I experienced a severe loss of power, all at once, and began spewing loads of carbon into the water. I couldn't increase the rpm's. I had the mixing elbow changed and the smoking stopped. The old elbow was badly coked (buildup of carbon) and was severely restricting the flow of cooling water and exhaust from the engine. The symptoms that I had was that over the last year, the engine was smoking all the time and even at low rpm's. Mixing elbows are deceiving - they look fine, but you can't see the buildup. The mechanic said that Yanmar recommends that the mixing elbow be changed every 5 years (don't total the hours, just every 5 years). I hope this helps. Good Luck.
I had this discussion with a good mechanic last week. It's possible that your engine is overloaded while operating. In other words, there is extra drag somewhere on your engine that causes it to create backpressure and overload the engine. Some causes are as follows: Barnacles or growth on the prop/shaft that causes it to overwork. Wrong prop for the engine (it could be overpropped), meaning that there is too much bite as the prop spins and would require reducing the pitch of the prop. Your mixing elbow could be coking up and causing back pressure. This is what happened to me. I experienced a severe loss of power, all at once, and began spewing loads of carbon into the water. I couldn't increase the rpm's. I had the mixing elbow changed and the smoking stopped. The old elbow was badly coked (buildup of carbon) and was severely restricting the flow of cooling water and exhaust from the engine. The symptoms that I had was that over the last year, the engine was smoking all the time and even at low rpm's. Mixing elbows are deceiving - they look fine, but you can't see the buildup. The mechanic said that Yanmar recommends that the mixing elbow be changed every 5 years (don't total the hours, just every 5 years). I hope this helps. Good Luck.
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Jon Petersen
Barnacles was my problem
Mine started to smoke and couldn't make it to the max rpm's .. last week.. dove down and looked at the prop and it was loaded with Barnacles that causes it to overwork. I had just painted the bottom 2 months ago. I had heard that Black magic marker on the prop would keep the barnacles off.. Tried it.. NOT! Well the bottom was clean except for the prop.. Hope this helps..
Mine started to smoke and couldn't make it to the max rpm's .. last week.. dove down and looked at the prop and it was loaded with Barnacles that causes it to overwork. I had just painted the bottom 2 months ago. I had heard that Black magic marker on the prop would keep the barnacles off.. Tried it.. NOT! Well the bottom was clean except for the prop.. Hope this helps..
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Bill O'Donovan
Mixing elbow
I second Paul Akers, but recommend changing the elbow every three years instead of five. It's unbelievable how it clogs up with carbon--hard as rock and completely impenetrable.
I second Paul Akers, but recommend changing the elbow every three years instead of five. It's unbelievable how it clogs up with carbon--hard as rock and completely impenetrable.
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Paul Akers
I painted my prop
Last week when I had the mixing elbow problem, the first thing the yard did was to send a diver down to check the prop for entanglements or barnacles. It was perfectly clean. I usually paint my prop with bottom paint. The mechanic said that I should never do that and the reason I would get barnacles would be because I don't use the boat enough. (But I work weekdays). The mechanic is good, but I beg to differ with him. I've tried it both ways - with and without paint- in different seasons. When I didn't paint it, it was loaded with the critters. I always paint the prop/shaft now. If it affects performance, then I don't notice it. I will continue to paint it in the future. Does anyone else have a different experience? P.S. Just don't paint under the zincs. This will insulate them from doing their job. Also don't paint the cutless bearing ends - water must get into the flutes for lubrication.
Last week when I had the mixing elbow problem, the first thing the yard did was to send a diver down to check the prop for entanglements or barnacles. It was perfectly clean. I usually paint my prop with bottom paint. The mechanic said that I should never do that and the reason I would get barnacles would be because I don't use the boat enough. (But I work weekdays). The mechanic is good, but I beg to differ with him. I've tried it both ways - with and without paint- in different seasons. When I didn't paint it, it was loaded with the critters. I always paint the prop/shaft now. If it affects performance, then I don't notice it. I will continue to paint it in the future. Does anyone else have a different experience? P.S. Just don't paint under the zincs. This will insulate them from doing their job. Also don't paint the cutless bearing ends - water must get into the flutes for lubrication.
Bill O., just FYI!
Bill O'Donovan: Just for your information, this coking problem is only prevelant in salt water. I believe it has something to do with the acidic exhaust, heat and the salt water comming together. This does not occur in fresh water if you run your engine at the recommended RPM's. Many of the boaters in salt water will also find that the jacket on the elbow will have rusted thru too. I like your idea of every 3 years. If the elbow is still good when you change it out, you should be able to have it boiled out and paint it so you have a spare for the next change out. If you wait for the 5-10 years that most boaters wait, there is nothing left to clean up for then next change out. The elbow is about $90 + the gasket. This assembly is NOT very easy to take apart. Removing the manifold and elbow from the engine is no problem. Getting the manifold and the elbow apart in a totally different thing. I would recommend a torch and two very large pipe wrenchs or a large bench mounted vice in place of one of the wrenchs to get the assembly apart. Other than that it is a relatively eazy project.
Bill O'Donovan: Just for your information, this coking problem is only prevelant in salt water. I believe it has something to do with the acidic exhaust, heat and the salt water comming together. This does not occur in fresh water if you run your engine at the recommended RPM's. Many of the boaters in salt water will also find that the jacket on the elbow will have rusted thru too. I like your idea of every 3 years. If the elbow is still good when you change it out, you should be able to have it boiled out and paint it so you have a spare for the next change out. If you wait for the 5-10 years that most boaters wait, there is nothing left to clean up for then next change out. The elbow is about $90 + the gasket. This assembly is NOT very easy to take apart. Removing the manifold and elbow from the engine is no problem. Getting the manifold and the elbow apart in a totally different thing. I would recommend a torch and two very large pipe wrenchs or a large bench mounted vice in place of one of the wrenchs to get the assembly apart. Other than that it is a relatively eazy project.
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Justin
I'd lean towards the prop
If your engine is fine, then I'd lean towards the prop being wrong. Terribly common problem. Previous owner probably decided they wanted to do 7 knots with a 1cylinder engine so they put a big prop on. Problem is your engine can't spin a big prop without overloading. If your Yanmar has a 1.95:1 reduction ratio on the transmission then you should have something close to a 12" X 7" prop. If you have a 3.00:1 reduction then you should have 14" x 10" prop. I suspect you have the former. Can you get max rated rpms out of the boat for short periods underway? If not then it is another sign the prop is too big.
If your engine is fine, then I'd lean towards the prop being wrong. Terribly common problem. Previous owner probably decided they wanted to do 7 knots with a 1cylinder engine so they put a big prop on. Problem is your engine can't spin a big prop without overloading. If your Yanmar has a 1.95:1 reduction ratio on the transmission then you should have something close to a 12" X 7" prop. If you have a 3.00:1 reduction then you should have 14" x 10" prop. I suspect you have the former. Can you get max rated rpms out of the boat for short periods underway? If not then it is another sign the prop is too big.
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Paul Akers
Before you say prop...
...ensure that it smokes ONLY when in gear. If you don't get smoke in neutral while you are reving, then you may consider it as a potential prop problem. If you get smoke when in neutral, for example, while you are charging batteries, then eliminate the prop as a cause. If you can't rev to full rpm's in neutral (and quickly), then continue thinking about the mixing elbow because this is a definite symptom that it's the elbow. And judging by all the parts that you've replaced, almost all other components can be eliminated.
...ensure that it smokes ONLY when in gear. If you don't get smoke in neutral while you are reving, then you may consider it as a potential prop problem. If you get smoke when in neutral, for example, while you are charging batteries, then eliminate the prop as a cause. If you can't rev to full rpm's in neutral (and quickly), then continue thinking about the mixing elbow because this is a definite symptom that it's the elbow. And judging by all the parts that you've replaced, almost all other components can be eliminated.
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Tim Farley
Thanks Black Smoke Help!!!
Thanks to everyone for their help. It sounds like I should change the mixing elbow. My prop is clean and the air filter is clean. Smoke happens in or out of gear. I will post what happens after I change the mixing elbow.
Thanks to everyone for their help. It sounds like I should change the mixing elbow. My prop is clean and the air filter is clean. Smoke happens in or out of gear. I will post what happens after I change the mixing elbow.
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bob skipper
one more thing to check
check to make sure your batteries are fully charged if you have more than one and they are bad or cant hold a charge between the alternator load trying to charge a bad battery and the load of the prop, bingo overload.
check to make sure your batteries are fully charged if you have more than one and they are bad or cant hold a charge between the alternator load trying to charge a bad battery and the load of the prop, bingo overload.
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David Schudel
smoking yanmar saga
My engine was smoking badly right before it packed up completely. I have a 3 cylinder Yanmar on a Hunter 33.5. It seems, though as yet not proven, the seawater injector elblow where the cooling water is injected into the exhaust is so badly corroded that it is massively restricting air flow causing smoking and finally the engine just wouldn't start. If your's is water injected check out the elbow (right after the heat exchanger). Mine is on order and I hope it fixes the problem. Dave
My engine was smoking badly right before it packed up completely. I have a 3 cylinder Yanmar on a Hunter 33.5. It seems, though as yet not proven, the seawater injector elblow where the cooling water is injected into the exhaust is so badly corroded that it is massively restricting air flow causing smoking and finally the engine just wouldn't start. If your's is water injected check out the elbow (right after the heat exchanger). Mine is on order and I hope it fixes the problem. Dave
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