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Universal M25 - black soot on water after startup

Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
MVIMG_20190421_162638.jpg

Hey guys, started my engine today and it shot out a clump of black soot which floated on top of the water for a while. It seems like the exhaust water has a stream of this grit in it as well. It's relatively recent, doesn't seem to be running hot, etc -- what could be causing this?
 

Pnelson

Member I
I’m curious about this too, as my m25 does this also. Seems to me it occurs more when weather is cool. Motor starts and runs fine, so I haven’t done any investigating. My fuel is now 2 years old so I am thinking old fuel may be a factor?
 

Alan Gomes

Sustaining Partner
View attachment 26721

Hey guys, started my engine today and it shot out a clump of black soot which floated on top of the water for a while. It seems like the exhaust water has a stream of this grit in it as well. It's relatively recent, doesn't seem to be running hot, etc -- what could be causing this?
It looks to me like it is unburned fuel mixed with some carbon deposits.

Does it do this only immediately after you start the engine or does it continue outputting this even after you are running it at speed? If the former, when your engine fires up does it get up to idling speed quickly or does it kind of chug for 3 or 4 seconds, slowly getting up to speed while it spits out this stuff?

I have a Yanmar 1GM, which I realize is a totally different engine. But if the governor works the same, this may be what is happening. When the engine is off the fuel rack is wide open, even with the throttle all the way back. While this may sound counter intuitive, this is because when the engine is off there is no opposing force from the governor spring, which relies on engine rotation to oppose the throttle spring in closing the rack. On my little 1GM, I find that if I don't give it enough throttle on start up, the fuel rack/injector pump will load up the cylinder with fuel in those first few seconds, which the engine cannot burn fast enough and simply spits out the exhaust. Then, once the engine gets up to speed (i.e., in maybe two or three seconds) these emissions stop. On the other hand, if I give it just a bit more throttle on start up so that it gets up to rotational speed more quickly, these emissions are greatly diminished or disappear entirely.

In any case, the only times I see this are: (1) When I start the engine without giving it quite enough throttle; and (2) When running the engine and I shove the throttle forward quickly from a low setting to a much higher setting. In both cases, the engine cannot burn the fuel as fast as the fuel rack/injection pump is sending it to the injector/cylinder, and it comes out as unburned fuel in the exhaust.
 
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Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
Alan - this was the first time I noticed the large black clumps, and zi accidentally started the engine with the throttle much higher than I'd usually set it.

I have noticed similar to you that if I don't throttle up a crack, it sounds like it's slow to kick up to idle speed. I had figured this might be related to a slow glow plugs, but that's a novice's guess at best.

I do believe that it continues after the initial startup though as I've noticed what I thought was a sheen when docking, but close inspection makes it look more like the dust / powder / particulates above.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Most of our boats have never had the fuel injectors serviced. I finally got around to it. Even though the spray pattern was reported OK after 30 years of service, the routine changing of the fuel injector heads has made a big different in ease of starting. The job is not difficult. http://www.ericsonyachts.org/infoexchange/entry.php?562-Ericson-38-Fuel-Injectors-Service

Soot is also said to be a product of our typically running at low RPMs. I am always happy to run the diesel at 80 percent+ of wide-open-throttle for a few hours. We want the temp gauge to get to max normal and stay there.

It's easy to lie awake over this stuff, but if you can maintain full speed and only get soot occasionally, it is useful to remember these are older engines, sorta like the ones that move our arms and legs, and some aches and pains are to be expected.
 

Geoff W.

Makes Up For It With Enthusiasm
Blogs Author
Most of our boats have never had the fuel injectors serviced. I finally got around to it. Even though the spray pattern was reported OK after 30 years of service, the routine changing of the fuel injector heads has made a big different in ease of starting. The job is not difficult. http://www.ericsonyachts.org/infoexchange/entry.php?562-Ericson-38-Fuel-Injectors-Service

Soot is also said to be a product of our typically running at low RPMs. I am always happy to run the diesel at 80 percent+ of wide-open-throttle for a few hours. We want the temp gauge to get to max normal and stay there.

It's easy to lie awake over this stuff, but if you can maintain full speed and only get soot occasionally, it is useful to remember these are older engines, sorta like the ones that move our arms and legs, and some aches and pains are to be expected.

I think fuel injector service is due, then. I am also smelling the exhaust much more frequently than I used to, which may be a silly thing to note as a concern, but could also signify fuel issues, I believe.

I have been running at low-ish RPMS lately (2000-2300) and can maintain 6-6.3kts there, and Puget Sound is cold water no matter what - maybe next time I go out I should give it a bit of an Italian tune-up.
 

Pnelson

Member I
I believe Christian identified my issue. We only motor in and out of the marina, and at low rpm, seldom over 1500. I am bound to be building up soot and possibly carbon. May need to pay more attention to running the motor a bit more often.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
About a decade after we bought our boat, I had the injectors out for testing. I recall that several had a poor spray pattern and all then got new nozzles. Not very expensive, altho I did pay a few $ for a professional mechanic to bring his torque wrench over and put them back. New "crush washers" are required also, as those are a one shot item.
Note that injectors are tested by shops where 95% of their work is truck related - so the cost is pretty much a "commodity" item price.

A good friend and diesel mechanic for 40+ years tells all of his sailboat friends to run their diesels for an hour under full load every month or so. This cleans out a buildup of carbon.
 

Tin Kicker

Sustaining Member
Moderator
A pro shop is needed to properly clean diesel injectors, as Christian wrote. The two problems are residue build-up and erosion of the tips. The tips can be cleaned with a solvent and brass or other soft wire brush, just do NOT use steel or stainless bristles. This does not address the erosion of the tips which is why a pro shop is really needed.

As an interim or to just address the residue, Seafoam and it's competitors are mostly naphtha and can be used like in this video. I've not done it with a boat diesel but have done trucks and it made a huge difference.

https://www.youtube.com/watch?time_continue=220&v=544E_X2oUgM
 

Baslin

Member III
When I pulled My Injectors last year, I didn't bother testing. For about $250 Bucks, I replaced all 4 of them. These injectors came straight from Kubota. I'm not sure what the cost of testing and servicing would be, but I thought if I was going to pull them out, new ones were going back in. I also replaced all 4 glow plugs at $7 a piece.....What really helped my engine's start time, was rewiring the glow plug circuit with 8 gauge wire and installed a high amp relay for activation. Glow plug time went down from 10 to 15 seconds, to about 4 to 6.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
I'm not sure what the cost of testing and servicing would be,

For testing and new heads only, the cost for four injectors was about the same--$200+ or so. With new injectors you could probably use the old double-nipples and the return and feed lines. I did. New crush washers are cheap.
 
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Baslin

Member III
I believe the injectors come with the new double nipple return line fittings. When I ordered mine (which I cant remember from who now) they came with the return line nipple fittings and new crush washers. Be sure and order new small return line hoses and the small hose clamps. These usually get damaged when removing. Also, be sure and put a little anti-seize on the injector and glow plug threads, and torque to spec.

When doing injectors, cleanliness is next to Godliness
 

Baslin

Member III
With new injectors you could probably use the old double-nipples and the return and feed lines. I did. New crush washers are cheap.

If the hoses can be removed without damage like Christian said, there is no problem reusing. Mine were a little stubborn.
 
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Leslie Newman

Guest
I know Yanmar recommends that you gun the throttle several times before shutting down the engine after idling to cool down. After letting my engine idle a few minutes after docking, before shutting down, I will throttle up to near max RPM, hold it a second or two, throttle down. Repeat at least four times. Then let it idle a few seconds and shut down. The previous owner said that he held the engine near max for 20 seconds, then at idle, then shut down. Whatever you feel blows the carbon out best. A friend spoke with someone that had years at Yanmar and he said that those engines want to be run hard. I think most diesels are the same.

When motoring I do make sure I run the engine at 80% and also adjust the throttle a few RPM periodically, as I think it best to not hold it constantly at one RPM the whole cruise.
I have many years experience with old (1949) Caterpillar diesels. Those engines hated to idle. The harder you worked them the better they ran.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
I've heard of the throttle-goose, but it may be a Yanmar recommendation. Never been able to confirm for Kubota/Universal.

Added: This is from the Universal Operation and Maintenance Manual Model 5411, 5416, 5424, 5432:

kubota .jpg
 
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Leslie Newman

Guest
Question is was that instruction written by the boat builder or is that from the engine manufacturer.
Plus, you do what works best. These diesels are meant to run hard, so blowing out some carbon before shutting down should be a good thing.
 

Alan Gomes

Sustaining Partner
Question is was that instruction written by the boat builder or is that from the engine manufacturer.
Plus, you do what works best. These diesels are meant to run hard, so blowing out some carbon before shutting down should be a good thing.
The Yanmar manual (or a few of the several manuals I have for the Yanmar GM series, at any rate) does contain the recommendation to run up the engine RPM several times to blow out the carbon at the end of use, before shutting down. I've owned two different Universal (Kubota) engines and don't recall the same recommendation there, but it seems to me that it would be a reasonable thing to do for any diesel engine.

As for the importance of running the engine hard, I'm going to post a separate thread about why this is important to do, based on a recent real-world (and quantifiable) experience related to oil consumption.
 
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Rocinante33

Contributing Partner
If I haven’t had the boat out for 2-3 weeks, I like to run th engine at the dock. When I do so, I make sure the dock lines are well secured and After it is warmed up, i shift it into forward, give it just some slight throttle and let it run for a minute or so. Then shift into reverse and again throttle up. I repeat this process about 3 times. So I am putting a bit of load on the engine, at least for 5-10 minutes and I am also exercising the transmission a bit.
 

Kenneth K

1985 32-3, Puget Sound
Blogs Author
As an interim or to just address the residue, Seafoam and it's competitors are mostly naphtha and can be used like in this video. I've not done it with a boat diesel but have done trucks and it made a huge difference.

https://www.youtube.com/watch?time_continue=220&v=544E_X2oUgM

The SeaFoam idea is interesting....especially since you need to refill the new filter with something if you don't want to spend an hour bleeding the lines.

Could refill with SeaFoam rather than fresh diesel. However, I did read that the lubricating properites of diesel are important for the guts of the injector pump. I'd guess SeaFoam is more of a solvent than a lubricant. Anybody tried this yet?
 
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