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Black smoke above 2500 rpm

Old 10-17-2009, 06:41 PM
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Default Black smoke above 2500 rpm

Hi Guys,

My Dad has a 30 foot boat with a Toyota diesel/Yamaha stern drive set up. It used to go along pretty well, but now won't rev above 2500 without blowing black smoke. We thought it was due to a build up of crap on the bottom, as is in the sea 24/7.

Have given it a clean but still has same problem. Have tried it under no load (in neutral) but seems to rev okay, so this leads to the stern drive.

Any clues as to what we can look at before getting the stern drive overhauled?

Thanks
Old 10-17-2009, 06:45 PM
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A dirty air filter? Is this engine turbo?
Old 10-17-2009, 07:02 PM
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fuel filters clogged
Old 10-17-2009, 07:23 PM
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Not the stern drive. It's either fuel or air. Start cleaning/replacing filters and go from there.
Old 10-17-2009, 08:46 PM
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With any diesel the most likley source of a problem like you describe is in the fuel supply. First I would replace the fuel filters and make sure there is no bacteria growing in the fuel tank. Next if the problem continues I would check the fuel injectors, if they are old they may need rebuilding or replacing. Good luck.
Old 10-18-2009, 05:16 AM
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Agree with BlackSober - black smoke is generally an indication of fuel and or injector problems.
Old 10-18-2009, 06:15 AM
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On gasoline motors, black smoke coming out of the exhaust means that the engine is running too rich / getting to much fuel.

Maybe this is the same on Diesel?
Old 10-18-2009, 06:25 AM
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http://boatdiesel.com/index.cfm?FM=1
Old 10-18-2009, 05:32 PM
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First question is did this happen suddenly with NO symptoms before? Had the boat been sitting for an extended period? I would disagree that the first place to start is the fuel system. First place would be the air intake/filter to check that it is clean and free flowing. Next would be to check that the turbo spins freely without too much lateral play. Third would be for a plugged up aftercooler (if you have one) and forth would be added load from dirty bottom, added weight to the boat or prop damage. THEN I would start looking at the fuel system. Plugged fuel filters will restrict fuel flow and cause a low power condition not black smoke under load.
Old 10-18-2009, 08:01 PM
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Sounds like a stuck turbo. I have had to free up a couple on semi's that were sitting for a while. If you can, take the intake loose at the turbo (if it has one) and see if it will turn. If it won't, rock it back and forth and see if it will free up.
Turbo's are amazing! They can spin 150-200,000 rpm and require turbo rated oil. They are extremely efficent too.
Old 10-19-2009, 05:06 AM
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Agree with the gents that recommend starting on the air side. Start with the intake and work your way back to the manifold.
Old 10-19-2009, 02:05 PM
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Black smoke is incomplete fuel burn

Most common cause is excess load. (too much fuel injected per power stroke)
Next is insufficient air. Will not allow given fuel charge to completely burn. Most common cause
is dirty air filter or bad turbo.
Next is bad injector. The injector tip atomizes the fuel into fine particles for combustion. If the injector
tip is damaged, fuel will not atomize and will not burn. Trying to push water through an injector
will damage the tip.

If you see black smoke only at high RPM prob turbo. Other causes will give you black smoke throughout the whole RPM range.

Last edited by 54bullwinkle; 10-19-2009 at 05:39 PM.
Old 10-19-2009, 03:09 PM
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I senond bulwinkle. Start with air filter, then to turbo impeller, then to injectors. You can pop test injectors easily, the Ford 6.9 motor in my old truck had to have the injectors tested every so often, my mechanic said it was an easy procedure. I'd say prop but it ran fine with that prop for many previous hours.
Old 10-19-2009, 04:21 PM
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Did toyota even make marine engines? Yanmar made the engines for their land rover, and converted those into the 6lp. But I wasn't aware toyota ever made marine engines...

Anyway, bullwinkle is dead on methinks........
Old 10-23-2009, 01:10 AM
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Default Thank Guys

Pretty overwhelmed by the quality and quantity of your replies, thanks again. Turns out it is a seized turbo. The boat was sitting for a while, I didn't hear the turbo whine last time we were out, but the gears didn't mesh in my head so to speak.

Anyway the old man kept taking the neighbors out for a run until he got one to sort it out! Anyway he will whip it off and take it in to Whangarei (nearest town) to get it looked at.

Cheers again
Old 10-23-2009, 05:39 PM
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The turbo's that I have freed up worked fine afterwards. I would at least try it, you will know once free if bearings are failing or a piece of trash is stopping it.
Repairs or replacement will be expensive.
Old 10-23-2009, 06:12 PM
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Air filter
Old 10-24-2009, 06:20 AM
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Kevin

Thanks for following up and letting us all know how it turned out. Really helps forum members learn

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