Pitch Black Exhaust Water Yanmar 2GM20F

[badsanta]

How is it in neutral at higher RPM? Does it still smoke? if not check that prop. Something wrapped around it will cause it to smoke. Or a clog in the exhaust elbow will do it also. If it ran fine last week and now it does not that in medical terms is an acute problem, as in a sudden on set. If you did not ad fuel from last time to this, I would change the filters yes but don’t overlook the exhaust elbow and the prop.

[hbergold]

Hi Rireefguy

I have the exact same engine with the exact same problem. Did you find what was wrong? Please advice before I end up disassembling the injectors.
Thanks in advance

Henning

Originally Posted by rireefguy

So I had some problems with my Yanmar 2GM20F today. I actually first noticed it the last time I took the boat out. The water coming out of the exhaust is PITCH black. Looks like dirty oil, but no slick. I changed the oil last weekend and the oil level has not changed. So I was out today and I was motor-sailing with the engine turning around 2500rpm when I noticed it again. I went down to idle and it goes clear again. Then (at the worst possible moment) the engine started running funny and was only turning 1200rpm at the same throttle position. I tired to throttle up and it bogged down. Ended up shutting it down and sailing home. Additionally, it has been a little hard to start. I dont have anything to base this on as it is a new boat to me and my first diesel but it just seems longer than I would expect, especially when the engine is cold..

Here is what I am thinking:

I think this is a fuel issue. The PO said that he never let it get down to 1/2 a tank, and would always keep it topped off. I now think that he may have been doing this for a reason. (I am currently at just under a 1/2 tank (was going to fill up today but never made it =))

I also thought about draining the tank and will probably still do that if this works.


The plan:

Going to change the fuel filters tomorrow and fill up with fresh diesel. See what happens



Does this sound like I am in the ballpark or am I totally off base. I am kinda new to diesels. If that doesn't do the trick where do I look next, etc.

Thanks in advance!

[hbergold]

Same problem, any advice from someone?

Greatly appreciated

Henning

Originally Posted by rireefguy

So I had some problems with my Yanmar 2GM20F today. I actually first noticed it the last time I took the boat out. The water coming out of the exhaust is PITCH black. Looks like dirty oil, but no slick. I changed the oil last weekend and the oil level has not changed. So I was out today and I was motor-sailing with the engine turning around 2500rpm when I noticed it again. I went down to idle and it goes clear again. Then (at the worst possible moment) the engine started running funny and was only turning 1200rpm at the same throttle position. I tired to throttle up and it bogged down. Ended up shutting it down and sailing home. Additionally, it has been a little hard to start. I dont have anything to base this on as it is a new boat to me and my first diesel but it just seems longer than I would expect, especially when the engine is cold..

Here is what I am thinking:

I think this is a fuel issue. The PO said that he never let it get down to 1/2 a tank, and would always keep it topped off. I now think that he may have been doing this for a reason. (I am currently at just under a 1/2 tank (was going to fill up today but never made it =))

I also thought about draining the tank and will probably still do that if this works.


The plan:

Going to change the fuel filters tomorrow and fill up with fresh diesel. See what happens



Does this sound like I am in the ballpark or am I totally off base. I am kinda new to diesels. If that doesn't do the trick where do I look next, etc.

Thanks in advance!

[cfoxcvg]

"hbergold"
Check the Prop. I had only a couple barnacles and it was about 30% of my problem which is the same you are having. See my post on "Cruisers Forum"

Yanmar 2gm20f - Black Water at 2700+ RPM by cfoxcvg

Unless you recently worked on the injector pump then disregard the talk about the shims. It only takes a couple little barnacles on the prop to over work the little 2gm20 but if the prop is clean she will work her but off.

[hbergold]

I will check this next weekend. I’ve heard the prop suggestion in other posts, but was lazy to get wet. I checked the mixing elbow (which wasn’t in bad shape), cleaned it, but the black smoke remains at 2700rpm. Will let you know. Thanks