Our 3ym30 has 300 hours on the clock. Today whilst motoring all was well until I increased the RPM to 3000 when lots of black smoke came out of the exhaust and I could hear a different noise from the engine. Reduce the RPM the motor runs fine. No overheating and no oil consumption. Any ideas?
Yanmar 3ym30 smoke at high revs
- Thread starter Brahmany
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Have you had it to 3000 rpm before?
If so and this is a change, first check the air intake for restriction, dirty or oil soaked filter, etc.
Does your engine compartment have enough openings to let combustion air in?
Try running with the air filter removed and then with a hatch open just to diagnose the problem.
If so and this is a change, first check the air intake for restriction, dirty or oil soaked filter, etc.
Does your engine compartment have enough openings to let combustion air in?
Try running with the air filter removed and then with a hatch open just to diagnose the problem.
Thanks for the reply guys. Unfortunately all the above things I have checked. The smoke is instantaneous when it comes too. It could be fine at 2800 and pouring out the smoke at 2850 !! There is a nasty engine noise at the same time which may be caused by all the unburnt fuel. Yes, I have run the engine at max revs. I often give it a squirt of full to throttle to stop glazing also. I will get it checked out ASAP but thought someone might have come across the problem with the yanmar before. Thanks.
I used to have a Yanmar as well. It was just a YSM10, 1 cylinder engine but I think that it is a characteristic of Yanmar's to blow black smoke at full throttle. The above post was right about the engine being overloaded. I recall that even the Yanmar owner's manual mentioned that if the engine blows black soot that it is overloaded & you must throttle back until it stops. Once the engine has reached its peak and/or max hull speed that its capable of, you will not go any faster. It does not matter how much fuel you give the diesel, once it hits its power curve and/or too much resistance it will just waste fuel & blow smoke. This is the engine's way of telling you to back off, or else. Your choice of prop & its condition can have a huge effect on engine performance. Do you have the standard 2 blade prop? or a replacement?
The issue is when the engine is not in gear as well. Push the throttle slowly and it will get to 3000 rpm, snap the throttle on it will get to 2500 before it splutters and blows smoke. cheers
Well, as has been hit on, this pretty much means either too much fuel or not enough air. The possible causes are numerous. But, the fact that this comes at a certain RPM regardless of load, and that it accompanied by a distinct sound, it could be the sign of something serious.
A poorly-balanced cam shaft, or anything else internal to the engine that was results in an imbalance, could produce this exact effect. To understand this think about a washing machine. You can load it up unbalanced and wait for the spin cycle. It will spin just fine up to a point, but at a certain RPM, the oscillations occur at just the right frequency to really shake to machine. The machine won't want to spin any faster because of the huge strain on the motor resulting from the wild oscillations.
If a motor is out of balance, the same thing happens. And, this sort of strain could well cause the incomplete combustion and thus the smoke you are seeing.
This certainly wouldn't be my first suspicion, but having ensured the air intake was unobstructed, and seeing that the symptoms came on at the same RPM regardless of load, I would certainly start thinking about the engine internals, and I would be very delicate with the engine until you've eliminated a balance problem.
A poorly-balanced cam shaft, or anything else internal to the engine that was results in an imbalance, could produce this exact effect. To understand this think about a washing machine. You can load it up unbalanced and wait for the spin cycle. It will spin just fine up to a point, but at a certain RPM, the oscillations occur at just the right frequency to really shake to machine. The machine won't want to spin any faster because of the huge strain on the motor resulting from the wild oscillations.
If a motor is out of balance, the same thing happens. And, this sort of strain could well cause the incomplete combustion and thus the smoke you are seeing.
This certainly wouldn't be my first suspicion, but having ensured the air intake was unobstructed, and seeing that the symptoms came on at the same RPM regardless of load, I would certainly start thinking about the engine internals, and I would be very delicate with the engine until you've eliminated a balance problem.
All sorted, thanks for the ideas. Problem was carbon in the mixing elbow. Cleaned it out and it goes to almost 4000 and no smoke. Supprised that 50 RPM was the difference from full on smoke and engine rattle and purring nicely. Live and learn. Cheers
Blowing Smoke
I also have a C320 but with a Perkins engine. I had a problem with symptoms a bit different but smoke, much smoke, was a feature in common. As mentioned by others, flow restriction can lead to richness but they did not cite flow restriction on the exhaust side as a possibility. My water mixing elbow was clogged. To start with, it has a tightly constricting orifice cast into it.
Richard
I also have a C320 but with a Perkins engine. I had a problem with symptoms a bit different but smoke, much smoke, was a feature in common. As mentioned by others, flow restriction can lead to richness but they did not cite flow restriction on the exhaust side as a possibility. My water mixing elbow was clogged. To start with, it has a tightly constricting orifice cast into it.
Richard
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