Help/Yamaha 250 4 stroke 2006 black soot problem

I own a 2006 pursuit cc3070 boat with twin Yamaha 250 4 strokes. When I start each engine a black soot comes out of the propellar exhaust a considerable amount which is very bad. I have used Yamaha factory technicians with laptops and all functions are normal. The engines themself ruin very well, no problem. I had the Yamaha tech shock each engine with Yamaha ring free. Also, added ring free 1 oz per 10 gallons in fuel tanks. This cured the problem for 1 week and now it's back. Meaning the black soot. I do not idle this boat. I basically start it and run it at 5400 rpm's most the time. This black soot problem is a real problem because it's effecting the envirnoment. It's not a little amount, it's a large amount. Can somebody help me with what might be causing this problem?

[boats.net]

Did the techs run a compression and leak down test, fuel pressure test? Did they check condition of spark plugs, are they black as well?

Help Yamaha 250 stroke

Thanks for your reply. I think the tests you talked about were preformed, but I will contact the mechanic to verify. Concerning checking the spark plugs being black, I don't think that was done. I will talk you ideas and talk to the Yamaha tech on it all.

same problem

Bump... I'm having the same problem without any fix yet. I've cleaned out the engines with sea foam, all tests performed, t-stats looked at, compression, etc. everything comes back fine. The fuel is non-ethanol based and is new, so it's not something jelled up.

The engine is running fine but I get a handful of debris shooting out the prop exhaust on startup.

Anyone else have this problem?

anyone else having this issue?

i still have the promblem any help out there?

tech says i might have bad fuel? but i ran tanks low re fueled and still have black soot1! any ideas?

[boats.net]

I'm not sure I haven't ran across this problem yet. If the engines are running ok then it's hard to tell what would be causing it to do this. I will check into it and see if I can find any information for you.

Soot is caused by one of two things. The first is buring oil, but has your engines are rather new I doubt that is the problem. The second is by running rich and I'll net that is the problem. You see all CCFI (computer con*****ed fuel injected) engines run in a close loop until they come up to operational temp. This richens mix much like the choke on a carb. Simply starting the engine and then going 5400rpms actually takes more fuel, and dumps more raw fuel, then letting them warm up the way your manual tells you to. If you want them to run clean then follow the instructions as set out in your owner's manual.

did they check fuel pressure at vst and lift pump make sure regulator on vst is working properly also make sure they do a vacume test on fuel system good luck

I Still Have The Issue With Black Soot On Starting Engine. I Put Ring Free In Fuel And Thsat Does Help!!!!

The ring free is good and is getting rid of carbon deposits so I dont know why your not seeing black stuff when using it. If I was anyone, I would use a can of seafoam on the hose and watch all the black carbon and crap come out. Then be sure to clean o2 sensors and plugs because after all the carbon going through the engine and out the exhaust they will all be fouled. But a good shock treatment of seafoam followed by a regular use of ring free or seafoam in the fuel is what I would recommend. BTW: ring free is more expensive but is used at 1oz/10gallons while seafoam is by far cheaper but used at 1oz/1gal.

I have a similar issue with my F150. It bleeds soot out the exhaust relief port, not the prop. Although, it seems to get better the more time I put on the motor. It has 112 hours on it now. The first twenty-five hours it bled an oily soot but that subsided as time built.
I think breaking this motor in during the winter had a lot to do with it. With air and water temps in the 40 to 50* range it may not have been getting to full operating temp and the rings took a while to seat.
I had it checked a few time and it always came back a perfect motor with no discrepancies.
The powerhead blew on this motor at fif**** hours in service due to the failure of the harmonic balance unit, old stock 2005 motor sold as new on a 2007 boat. Yamaha replaced the powerhead.
It wouldn't turn enough RPM so the factory tech lowered the motor two holes and changed the prop and it turned 6000 rpm that day of water test only. After that it would only turn in the 52 to 5400 rpm range. They checked the motor and said nothing was wrong.
After some time I raised the motor one hole and again it turned 6000 rpm the day I tested it. Then again, it was back in the 52 to 5400 range without any changes. I figured all this, the low rpm and sooting was a common issue so I took it back. They tested everything except fuel pressure or vacuum. The mechanic said that had to be done running WOT so he ask yamaha to send a tech to water test. That never happened because it wouldn't code anything and the leak-down proved good. Who knows, I'm going to run the crap out of it until it pukes again. Glad I have the six year warranty.

I am having this same problem when i come home and flush my F225's. I think as these motors are only 20 hours old it is running rich. They perform well but are using more fuel than they should.....Any solutions yet?