yanmar 2gm carbon out of exhaust??

[keltdeano]

Hi All

My yanmar 2GM starts first time as always. On motoring the other day she would not rev past 1700 RPM the exhaust smoke was white (not thick just normal clearish). I was barley moving as going against the wind(but not tide) only making a knot if that.

The temperature and low oil pressure alarm did not go off but I was alarmed to see what at the time I thought was oil coming from the exhaust out with the expelled raw water. It looked awful.

I had to continue as she was booked for a lift out.

I made it (just) as by now she was completelty gutless.

I have checked the oil and since realised that the black being expelled was actually carbon as she hasn`t burnt a drop of oil thankfully.

The bottom and prop were exceeding weeded up so I can assume this has strained the engine.

My question is other than an oil change should I be doing anything else? Breathers or such?
The engine was treated to the usual oil and filter changes it was serviced earlier this year, and in the last 2 years has had new: Lifter pumpInjector pumpValves seats regroundThermostatExhaust elbowStarter motor.

I will be going in with a nice clean bottom the weed was a foot long!

Is there anyhting else anyone recommends doing to the engine before she goes back in? Decarbon/flush or something?


Thank you all

[Compass790]

Welcome to the forum keltdeano,
Whats happening there is you are overfuelling. The load on the engine is too much from the added drag from the weeds & you push the throttle too far so it squirts more diesel into the chamber but the revs cant rise as the load is too great. There is not enough air to completely burn all that diesel & it gets expelled partially burnt hence all the black soot.
Dont need to do anything to the engine most likely. The other things that can cause that problem are loss of compression, blocked exhaust elbow or failed injector but all much less likely than overload. Ask again if the problem is still there after you've cleaned the boats bum but I'm picking it will be fine.

[S-V SAGA]

Had the same issue at the end of last season, caused by a bumper crop of barnacles.

[keltdeano]

Thank you, relieved to hear this 😊