outboard releases black powder on water

[dradulescu]

Hello,

I have an Merc 115hp EFI.
After running 30-60 minutes on 5000-5500 rpm, after taking a short break when I restart the outboard it leaves like some black powder on the water for the first seconds.

What could be the reasons ?


Best regards,
Dan

 

[86 century]

Re: outboard releases black powder on water

Welcome to Iboats
It could be a build up of carbon. If you go the outboard forum at the top in the adults only there is a procedure to clean it out.
Carbon will build up over time due to unburnt oil and junk in the gas.
Good luck

 

[dradulescu]

Re: outboard releases black powder on water

Hello and thank you for your answer.

Well the point is that is not releasing the black powder after each start, but only when restarting after a long run with high rpm.
That would exclude a build up in time, and would suggest a build up of something during that 30-60 minutes run.
The outboard is not eating oil, after 100 hrs I did not have to add more oil.

 

[portd]

Re: outboard releases black powder on water

I have that motor in a 2002 model it does that as well maybe not as often , i thought is was from the exhaust but not sure

 

[Faztbullet]

Re: outboard releases black powder on water

That is a sign of it running rich. thing that will cause that engine to run rich are: 1)clogged intake screen 2) defective temp sensor 3) sticking injectors 4) very worn sparkplugs
If it was in my shop I would check screen ,temp sensor, and plugs as they sometime will tell you if a injector is sticking. If every thing checked out I would send them off to be cleaned and balanced as there is no 'snakeoil" that will clean debris from filter in injector.