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Old 05-08-2012, 10:34   #1
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Yanmar Black Smoke

Yanmar 3GM30F blows black smoke and is RPM limited to about 2700 RPM under load in forward. Looks like the engine ingested the foam material around the air filter. I vacuumed the air intake, but did not observe any filter material in the vac. Engine starts and idles fine. In neutral I can reve the engine to 3600 rpm with no smoke. In drive it losses power and begins smoking at around 2700 rpm.
Prop was just cleaned a couple of weeks ago. What could be the cause of the load at higher Rpms? Could the stuffing box nut be too tight? HELP Please!
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Old 05-08-2012, 11:01   #2
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Re: Yanmar black smoke

You probably has one of those elbows just past the heat exchanger and it has carboned up. It's easy to remove, spray a generous amount of Decarb cleaner into it and problem solved.

Needs to be done approx every 200 hours and Yanmar now recommend that for every hour of motoring, run at full revs for 2 minutes, which helps clear the carbon build up.
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Old 05-08-2012, 11:02   #3
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Re: Yanmar black smoke

p.s. Not knowing how technical you are, if you need photos of the elbow - I can post them for you.
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Old 05-08-2012, 11:07   #4
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Re: Yanmar black smoke

Black smoke from a diesel is an indication it isn't getting enough air. I think you need to look further into the air intake system. That foam went somewhere. I had the same symptoms when the turbo on my engine quit. Black smoke as I advanced the throttle past idle and lower top end RPM's.
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Old 05-08-2012, 11:17   #5
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Re: Yanmar black smoke

either LACK OF USE or BAD ELBOW or INJECTOR or AIR CLEANER....btdt with 2qm....i vote for lack of use first.
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Old 05-08-2012, 15:15   #6
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Re: Yanmar black smoke

Just cleaned out the mixing elbow. A little carbon/suet, but not enough to cause the issue. Engine starts, idles and rev fine in neutral. Does fine in forward till about 2700 rpm, then starts producing black smoke. Ron's in reverse at 3000 rpm just fine. Maybe I have a colony of critters on the underside of the keel that the hull cleaner didn't see when he cleaned the hull. Any other ideas?
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Old 05-08-2012, 15:59   #7
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Re: Yanmar black smoke

If the engine will only run to 2,700 rpm in forward but will run to 3,000 rpm in reverse, that sounds like a fouled prop to me.

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Old 05-08-2012, 16:44   #8
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Re: Yanmar black smoke

This could also be an over-pitched prop. If it runs normally and revs to 3600 without smoke in neutral, but sends out black smoke and won't rev fully, the smoke may be incompletely burned fuel due to the prop holding the revs down. What kind of prop do you have? If it's a folding prop, is there any prospect that they messed with the pitch when they cleaned it?
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Old 05-08-2012, 16:54   #9
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Re: Yanmar black smoke

When my fuel filter became clogged with gunk, had exactly the same issues and at about the same RPM. Engine ran fine no load but belched black smoke when I went past 2500rpm and would max out at 2700. Previously it ran fine to 3600 rpm.
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Old 06-08-2012, 09:28   #10
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I would try something real basic. Add a diesel injector cleaner in your fuel and replace the fuel filter if it has not been replaced for some time.

Black smoke can be caused by numerous things. Air/ fuel mixture, dirty injectors, valve clearances, poor quality fuel, etc. I would rule out the most basic causes before I start tearing apart the engine.

I use a fuel additive the keeps my injectors clean as well as my filter. I have used it this season for the first time and it seems to work for me.
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Old 07-08-2012, 06:36   #11
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Re: Yanmar black smoke

If fuel air mix were the issue, wouldn't the engine also smoke when reved in neutral?
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Old 07-08-2012, 06:55   #12
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Re: Yanmar black smoke

I agree with: zeehag, tartansail, & roverhi: all likely simple solutions. Capt.Fred
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Old 07-08-2012, 09:25   #13
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Re: Yanmar black smoke

Am I the only one who thinks the fact that the engine ingested a foam air filter might have anything to do with the problem?
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Old 07-08-2012, 09:31   #14
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Re: Yanmar black smoke

How long have you owned the boat, and has it ever reved up to 3400 in gear?
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Old 07-08-2012, 09:32   #15
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Re: Yanmar black smoke

Quote:
Originally Posted by HopCar View Post
Am I the only one who thinks the fact that the engine ingested a foam air filter might have anything to do with the problem?
Nope!
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