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Old 14-01-2020, 01:05   #1
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I've tried Everything....Yanmar with Sooty exhasut

I reckon I've tried everything to stop the soot deposit on the stern of our old girl. We have a Yanmar 2GM20 on a 30ft Chico and we get a soot build up on the stern after running for say 30 to 40 minutes.


This is what we've done so far to try and resolve this problem:


1. Check to make sure fuel is clean - empty tank and fill with clean fuel
2. Check and make sure the prop is not oversized - engine revved to 3400 but still had prop tweeked so now revs under load to 3500
3. Check to make sure there is plenty of air getting to the intake - new intake duct
4. Check to make sure the exhaust system is ok - new Mixing Elbow clean/new pipework
5. Test injectors - replaced injectors
6. Check compression - bit low on one cylinder (380psi and 340PSI)
7. Tried running at higher RPM - ran for couple of hours at 2800RPM no change


8. Getting serious now as I hate not being able to figure things out.....


9. Full strip down and inspection
10. New piston rings and bores deglazed by professional all miked and found to be in good condition well within tolerances. New bearinsg and head gasket etc.
11. Check diesel injector pump - sent in to specialist diesel workshop, all tested and re-set
12. Still sooty exhaust deposits.....Now surely I must be missing something because the problem persists but now I think it must be a simple thing thats wrong...?

Anyone got any ideas? Please???
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Old 14-01-2020, 02:58   #2
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Re: I've tried Everything....Yanmar with Sooty exhasut

Seeing that you've checked everything and all seems to spec, I'd double check that the timing is set to 15 +/- 1 BTDC, and providing it is, go back to point two, over-propped.

Different engines perform differently under specific loads; the high idle speed for the 2gm is 3725, max load rpm is 3600. Given that you're tried everything else, seems the only thing left would be to prop for 3650 in gear and see what happens.

Many people say that you're propped right with a diesel when you can reach 100 rpm over rated maximum in gear, and my experience bears that out, though there is much variation involved, regarding manufacturer, application, life expectancy, etc.
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Old 14-01-2020, 03:33   #3
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Re: I've tried Everything....Yanmar with Sooty exhasut

What about running cold, not getting up to temp? Can that create sooting?
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Old 14-01-2020, 03:51   #4
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Re: I've tried Everything....Yanmar with Sooty exhasut

Probably faster and cheaper to put a particulate filter into the exhaust. Lol.

Are you seeing massive smoking or is there just diesel soot buildup?

If it's just diesel soot buildup bothering you aesthetically, maybe wax the area really well and give a quick wipe after motoring?

Maybe also extend the exhaust outlet a bit farther than the hull?




You could go mad trying to get a diesel engine to leave no trace of soot.
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Old 14-01-2020, 05:50   #5
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Re: I've tried Everything....Yanmar with Sooty exhasut

Had soot from my Yanmar.
This solved the problem:
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Old 14-01-2020, 10:10   #6
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Re: I've tried Everything....Yanmar with Sooty exhasut

For what it is worth......
- The 2GM20's ran cold unlike the 2GM20F versions which tended to produce soot.
- The panel tachometer may be far from accurate and the engine may be actually over propped. Check with a mechanical test prop or equivalent.
- The diesel may be old fuel and past its prime.
- I have great success by using Stanadyne Performance Formula diesel fuel additive at double the normal dose ( 4% ) which will also mitigate the fuel oxidation issue.
There may be a restriction in the air intake system or the air intake filter foam cone may be deteoriated if fitted.
Cheers,
Niall.
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Old 14-01-2020, 10:17   #7
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Re: I've tried Everything....Yanmar with Sooty exhasut

We have the same issue with our Yanmar 4JH-TE, and have had for a lot of years. It gets worse as eng (and boat) speed increase and the stern tucks, putting the exhaust farther under water. And yes...we've tried exhaust extensions-both floppy(fire hose trailing behind, and fixed)....did no good, the exhaust curls back around and still gets on the transom. We've talked to several different mechs over the years, and no one seems to have an answer. It comes off with Starbrite Polish w/PTEF, or with "H-7". Never heard of/tried Diesel Kleen-but will look for it....how much do you put in a tank?
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Old 14-01-2020, 13:20   #8
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Re: I've tried Everything....Yanmar with Sooty exhasut

I'm not familiar with the Yanmar but had a similar soot problem on an engine some time ago caused by poor injection pattern. The injectors had been serviced but the problem persisted, we eventually found that the injectors were not seated correctly in their pockets due to additional copper seating washers i.e the old copper washers had not been removed with the injectors but new ones had been fitted. This meant the injectors tips were too high and the fuel spray was obstructed.

Just a thought!
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Old 14-01-2020, 13:29   #9
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Re: I've tried Everything....Yanmar with Sooty exhasut

My initial thoughts are that the thermostat is malfunctioning, always open, running the engine too cold.

Any air filters I would remove for testing.

My smoking went away with a new exhaust injection elbow.

Good luck!
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Old 14-01-2020, 13:57   #10
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Re: I've tried Everything....Yanmar with Sooty exhasut

Quote:
Originally Posted by s/v Jedi View Post
My initial thoughts are that the thermostat is malfunctioning, always open, running the engine too cold.

...........
Good tip!

I had a 2GM20 with a failed thermostat which ran cold which resulted with smoke deposits on the stern.

The easiest way to tell is to pull the thermostat and test in cold/hot water. It should start opening ~50C and be fully open at ~60C.
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Old 14-01-2020, 14:06   #11
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Re: I've tried Everything....Yanmar with Sooty exhasut

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Originally Posted by Wotname View Post
Good tip!

I had a 2GM20 with a failed thermostat which ran cold which resulted with smoke deposits on the stern.

The easiest way to tell is to pull the thermostat and test in cold/hot water. It should start opening ~50C and be fully open at ~60C.
I believe my Yanmar and Northern Lights diesels run at 80C work temperature.
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Old 14-01-2020, 15:00   #12
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Re: I've tried Everything....Yanmar with Sooty exhasut

I would suspect you're running too cold. Check/replace thermostat.
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Old 14-01-2020, 15:40   #13
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Re: I've tried Everything....Yanmar with Sooty exhasut

Quote:
Originally Posted by s/v Jedi View Post
I believe my Yanmar and Northern Lights diesels run at 80C work temperature.
Yes but they will be coolant engines with a heat exchanger, am I right?
Raw water-cooled engines cannot run higher than 60oC due to salts precipitating out at higher temps
I believe the OP's engine is raw water cooled.
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Old 14-01-2020, 15:58   #14
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Re: I've tried Everything....Yanmar with Sooty exhasut

I had an ongoing similar issue with a different model Yanmar. Stanadyne every tank! Did all the logical things you did, even had to replace an engine for another reason. The over prop though is one that always comes up and once confirmed to be as recommended, still no real change. Try offloading the boat to bare necessities. Once I remove what must have been hundreds of pounds of line, etc. the speed increased 5 to 7 knots and less smoke. Worth a try.

Brian
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Old 14-01-2020, 16:03   #15
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Re: I've tried Everything....Yanmar with Sooty exhasut

Was the compression rechecked after the new rings were fitted? 340 psi is way low.Were the valves ground? Have the tappet clearances been rechecked? Timing as in post 2.
Sounds like you have gone thru all the usual causes. Our yanmar used to smoke with low compression but after rebuild was cured.
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