Yanmar 1GM10: Loss of power and black exhaust water

[Triton24]

Hi,

I have black water coming out of the exhaust (soot particles, no oil) and propulsion is only about half of what it used to be.

I have checked the following:
- Exhaust elbow inner tube is NOT corroded. But a lot of soot is visible inside tube and where the elbow joins the cylinder head (see pictures)
- No corrosion visible at the cylinder head when the valve cover is taken off.
- Oil has normal color and fill level (see picture).
- Engine running at 3,000 RPM with transmission NOT engaged: no black soot at exhaust.
- Engine running at 3,000 RPM with transmission engaged: black soot at exhaust.

Any ideas and directions to point me in? Much appreciated.

Cheers
Roland

[Wotname]

Try checking the rest of your exhaust system for carbon build up.

[lockie]

A heavily fouled prop is one of many possible causes. If the engine will rev to 3000 under load, it can't be in too bad shape, and is able to develop power.

[skipperpete]

Hi Roland, a fouled propeller would be a possibility but don’t rule out the parasitic load of the alternator either. If your propeller is clean and not the culprit, try briefly running the engine with the alternator belt either loose or off completely to eliminate that as a cause of the soot.
Pete.

[tkeithlu]

On acceleration of the engine? If so, consider the possibility that you have worn injectors, or are otherwise delivering too much fuel to the cylinders.

[PaulvR]

Clean the air filter?

[Nord Sal]

I have seen an air filter clogged with soot do this. (bucket was left covering dry exhaust stack).

[Ivansgarage]

Originally Posted by PaulvR

Clean the air filter?

or Bad Injector squirting , dirty, try injector cleaner

[Triton24]

Thanks for so many good ideas. It turns out that it was the prop that was covered in barnacles. Never expected this to have that much of an effect.

[Wotname]

Originally Posted by Triton24

Thanks for so many good ideas. It turns out that it was the prop that was covered in barnacles. Never expected this to have that much of an effect.

Thanks for the update.
You should now be able to more than 3000 rpm at WOT!

[Daniellago]

Hello friend,
I had the exact same issue. I was already ready to spend a lot to fix it.
It turns out it was the barnacles in the propeller too.
Thank u very much for the tip!

[Wotname]

Welcome aboard CF Daniellago.