Yanmar Cooling Water Discharge

[Willy1805]

Is it common to see oily discharge water from the cooling discharge on stern? It seems that there is a greyish colour in the water, I am making an assumption it is likely oil. Do I need to be concerned?
cheers
Willy
thank you all for your quick replies... I took a water sample of the discharge, and they re particles and have concluded it is carbon .... I have been told that carbon is common in diesels.. and what I have is a carbon build up.. that needs to run at 80% to max RPM for 30 - 45 min .. i have also read in the manual that the engine needs to cool down before shut down and therefore I should run it at low RPM for five minutes and then rev up to max RPM and then shut down immediately..

I do not think I have a problem other than carbon build up... thank you all

 

[Alan]

Yes. You should be seeing clean water coming from the exhaust. If oil is being discharged you need to have your engine checked.

 

[n624ma]

Gray Discharge

It may be soot. Oil would disperse on the water and leave a rainbow sheen.

If you are seeing it at start up and and you you have to run at low throttle prior to shot down, a typical duty cycle, see if it clears up after several minutes.

A real good test is to run the engine under load by motoring at 75~80% RPM for about 30 minutes then shut down and restart and take a look.

 

[seadaddler]

Most Diesels Do

It most likely is fuel residue and some oil residue,most diesels give off exhaust residue and they are not the cleanest burning,a cleaner mixing elbo,fuel filters,air cleaner will let the engine perform better and less residue.
Keep checking the oil,most diesels will give off a little residue.
Nick

 

[Andy1237]

Check air intake and injectors

Yanmars burn pretty clean so a noticeable oil is something to look into. Check simple things first, is air intake blocked and preventing a full burn of fuel due to lack of air? And then it could be a little more-Your injectors could be over fueling and need new nozzle tips. Pretty easy fix for anyone familiar with diesels.
Whats happening? The injectors should "pop" and spray a mist of fuel at about 2200psi. After they get old or scored from dirty fuel they spray at too low psi or dripple instead of spray and too much fuel goes in.