Yamaha 4 Stroke Soot

[ktcarter00]

I have a 2005 200 HP Yamaha 4 Stroke with a little over 60 hours on it. As long as I've had it, it has produced a black soot out of the exhaust port that drains down the back of the motor. The dealer has done every test imaginable with no results. Yamaha says its normal, yet i can't find another one anywhere that does it. The motor is in spec and the thermostats test fine. Any suggestions? I have pictures if that would help.

 

[WillyBWright]

Re: Yamaha 4 Stroke Soot

How do you run it? Long periods of running below planing speed would do it. If the motor is running hard enough to plane the boat, the burn is more efficient and the exhaust is being drawn out the prop rather than out the relief holes.

 

[ktcarter00]

Re: Yamaha 4 Stroke Soot

Normally cruise at 4200 RPM. It will build up after 30 minutes or so.

 

[Triton II]

Re: Yamaha 4 Stroke Soot

Hmmm, just a thought - may be worth changing the oil and draining the old fuel and putting in some fresh fuel. Does the motor use oil at all?

 

[ktcarter00]

Re: Yamaha 4 Stroke Soot

No. It doesn't use oil. Oil has been recently changed. Even attempted to lower the level of the oil in the crankcase but no difference.

 

[Triton II]

Re: Yamaha 4 Stroke Soot

It sounds like it's running very rich if it isn't burning any oil. Is the fuel consumption within specs and how do the plugs look? Sounds like you need rodbolt for this one!

 

[rodbolt]

Re: Yamaha 4 Stroke Soot

a certain amount of soot is normal. its called carbon and it forms when gasoline burns. but if its an abnormal amount, i cant see it from here, then your going to have to find a dealer with some techs that understand 4 stroke systems and have the laptop to monitor stuff like temp,pulse width,timing,air pressure and all the rest of the sensor inputs.<br /> you will also need a fuel pressure gauge to check the injectors for leakage.<br /> some hulls tend to pull the exhaust gasses back worse than others. but most any of the 4 strokes that run offshore and back have soot on the back.<br /> but if its abnormal its running rich. make sure all the sensors are plugged in and working correctly. occasionally if a sensor is not functioning it will go a bit rich.

 

[ktcarter00]

Re: Yamaha 4 Stroke Soot

Thanks. This motor is releasing, in my opinion, an abnormal amount of carbon. We have a total of 7 Yamaha motors (3 four stroke, and 4 OX 66) in our family, and not a one of them does this. Also, our marina probably has in excess of 100 of the 225 and 200 HP 4 strokes and I haven't noticed a one of them doing what his motor is is. I learned today, a Yamaha tech is coming to see it first hand. I'll post his observations.

 

[alumacomp]

Re: Yamaha 4 Stroke Soot

I had excessive carbon build up on the prop hub of my 2002 Yamaha F115. Turned out to be running rich because of a faulty thermo assembly(sensor).

 

[ktcarter00]

Re: Yamaha 4 Stroke Soot

Thermostats were removed and tested for proper opening and closing temps and were within spec. Pressure control valve was also inspected and found to be functioning properly.

 

[rodbolt]

Re: Yamaha 4 Stroke Soot

I care not about the t-stats. what is the thermosensor telling the computer and what is the puter doing with the info.<br /> without the laptop your sunk as far as checking the fuel pulse width.<br /> if it runs well and slightly rich odds are a temp sensor or air temp sensor is no quite right. the TPS voltage could be a bit off as well and on 2 occasions I have seen fuel pressure to high. but usually that has other issues as well. on a motor that new with the problem you describe a better test for the t-stats would have been with the IR gun. we were fairly sure they worked we just want to see if the block is actually coming up to temp.<br /> good luck with a tech rep, ya may need it