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Solitude 27-02-2010 14:27

Yanmar 1gm10 - Blue Smoke - Help!
I started up my raw water cooled 1GM10 today and started seeing a oil sheen on the water and some blue smoke. 1400hrs with good maintenance and I run it at 2700.

This is new and the engine was not burning blue or consuming oil last fall. I know this isn't good.

The smoke is defiantly blue from at about 2500 rpm. I believe it is consuming oil but need to run it longer to be sure.


Why did this happen now? There is no water in the lube oil, it runs well. Last fall i changed my exhaust mixer and brusher carbon out of the exhaust port. Could I have knocked some deposits into the valves or something?

Could someone guide me in some trouble shooting so that I could narrow down where the oil is coming in.

From what I have read it could be .

Piston rings?
Valve guides?

I ran anti freeze in it last fall and it didnt get cold here in Vancouver

Im going to start it and open the oil fill cap to check if I can feel some excessive pressure.

um saudade 27-02-2010 14:38

Blue from oil or blue from low compression or a little bit of both? You may have some sticky rings causing low compression. Did it start well and as usual? Is it getting up to temp? Crankcase pressure/blowby? How old is the oil in the crankcase and is it the right stuff(diesel rated?) Not enough info.

Solitude 27-02-2010 17:09

Here is some more info.


I changed the oil just before winterizing and then started and warmed it up and changed it now. Its proper 15-40 Penzoil Diesel rated.
It was hard to start after sitting the winter. I hand cranked it first to get some oil moving in it after sitting. I bled the air out and it started up. It now starts fine everytime and runs very well.
It does get up in temp ( I changed the impler and zinc) Good water flow out the exhaust (remember its raw water cooled). I have serviced it properly the past 3 years.

As far as blow by and lube oil consumption. I just went down to check a few more things.

Lube oil consumption I ran it for 1/2 hour and there was not a huge difference on the dipstick and it is hard to say if it used more than a millimeter or two during the time.

Blow by: I took off the oil fill cap while running at 2000 rpm and at idle. There was no smoke comming out at all. There was a pos/neg pressure from the piston of course. I also believe there was more pressure blowing out than in.

At anything under 2000 there isnt a great amount of noticable smoke but there is a slight grey blue tinge to the exhaust.

If i rev it up 2500 2700 i get an initial puff of `blue ish grey smoke followed by a steady but somewhat less amount of blue grey.

I always get a sheen of oil out the exhaust.

I would like to repeat that It did none of this prior to winterizing it. No white grey blue or black smoke before.

The one good thing is I have alot or room to get to the different parts of the motor front, back and sides.

I do have some mechanical skills but with cars.

Chief Engineer 27-02-2010 19:59

Once old is the exhaust elbow?

Solitude 27-02-2010 23:04

I changed the exhaust elbow in the fall when I winterized.
This is the first time I started the motor with the new one on.

During the change i brushed out carbon deposits in the exhaust port in the head. Could I have damaged the exhaust valve? I dont think I touched it. Carbon deposits sticking to the valve seat maybe?

Ex-Calif 28-02-2010 00:42

Go out and run it hard for about 2 hours. Pay attention to temps and oil pressure.

Do a before and after dipstick reading.

Are you sure it's blue and not blackish? Did you reprop, change packing glands, tighten packing glands or do anything that might add more load to the engine?

Prop is free and clear and rotates easily by hand in neutral?

Engine makes full power and RPM?

never monday 28-02-2010 07:39


Originally Posted by Chief Engineer (Post 411636)
Once old is the exhaust elbow?

1GM's have less of a problem with elbows than the U shaped elbow used on other small Yanmar's.

Solitude 28-02-2010 09:51

Hi Ex Cal, Never Monday, Chief

It really has no black in the smoke all. I have not re-propped. Would a greater load create blue smoke?
Prop rotates free.
It does it warm and cold.
I ran it at the dock and in gear for the test. I can bring the engine up in RPM with out hesitation or problem both in and out of gear but I havent had it out for a sea trial yet.

It starts and runs great.

It always leaves an oil sheen on the water. Blue Smoke is seen when its in gear at 2500 + rpm or when reving quickly. I cant remember if it does it out of gear at 2500

I read if it was a load issue it should be black or dark grey.

Everything is staus quo from last season on the motor and drive train except the new exhaust elbow, impeller, oil change, sprayed fogging oil in the intake behind the aircleaner.

The exhaust elbow is completely new. I did scrape carbon out of the port in the head.

Could carbon deposits fall through the exhaust valve and score the cylinder? These problems showed up right away when I started this year and there was no smoke of any kind last year when I shut it down.

I took the aircleaner off and wiped it out and ran the motor with it off. It didnt make a difference.

I can try to take it out and run it at cruising for a couple hours.

Everything I read says blue smoke is rings or valves? But how would these problems just show up after sitting the winter? It wasn't cold. I turned the motor over by hand several times during the winter.

I have read about stuck rings? Is this something? Is there a treatment?

I geuss the big test is if the lube oil drops when Im out, but from what I have read blue smoke only comes from burning lube oil.

Any ideas? Like I said it was fine last season.

Boracay 28-02-2010 14:25

Straight 30 weight...
Have you considered switching to straight 30 weight mineral oil (provided it's allowed by Yanmar).

Solitude 28-02-2010 14:28


Originally Posted by Boracay (Post 412046)
Have you considered switching to straight 30 weight mineral oil (provided it's allowed by Yanmar).

I have been using the Yanmar specified 15-40. Its Raw water cooled so I can see a need for the 15w when cold. It just started and something must have caused it. I cant have worn out over the winter.

ConradG 28-02-2010 14:38

If blue, it's oil. If it's been sitting for the winter and just started, don't get too nervous yet. The oil rings may be stuck. The should loosen with use and start sealing again. If it is huge clouds it would be one thing. Can you see oil usage on the dipstick? Is it bad? How does the oil smell? How is power? Could the oil level be even a touch high? (causing un nescessary bolwby) Is there excesive oil in the air intake coming from the blowby tube?
If power is good, I'd run her (hard) for a few hours and see if things clear up. Sometimes engines find use oil until they find their spot on the dipstic and will go right through to the next chage without needing to add any. Don't add unless you need to.

Chief Engineer 28-02-2010 17:29

I ran it at the dock and in gear for the test. I can bring the engine up in RPM with out hesitation or problem both in and out of gear but I havent had it out for a sea trial yet.

This is what we called on the Tugs "Testing at dead push".

As you bring the RPM up you have full load on the engine. The injector pump is trying to put more fuel thru but it is not all burning....hence the fuel sheen.

Run it underway and report back.

ConradG 28-02-2010 17:33

The Italian tune-up!

Solitude 28-02-2010 18:15

Thanks Guys

I didn't have time to go out with it today (final in men's hockey here in Vancouver).

Im going out Wednesday for a sea trial and will top off the oil befor I go, run it for 1 hour or 2 at 2700rpm and measure the oil level when I get back.

I did run down to the dock. I wanted to try one thing. I started it and it fired up right away but stalled, cranked it a few more times and in a puff of dark grey smoke it started.
It does not produce smoke when out of gear but the oil sheen is still there (I know its not good for the engine to rev up without a load) I could bring it up to 3000 and back without smoke and I didnt want to go higher but could of.

Does this help with diagnosis? I also feel that it just as hard as before to turn the engine over and almost imposible to crank it with the hand crank. Compression ok? or is that too blunt of a test.

Thanks so far...

ConradG 28-02-2010 18:23

As Chief engineer sais, it could be pushing unburned fuel. Stcky injector or just loaded. I would just run it for a good bit and see if things loosen up after the rest it has had. Fuel nowadays isn't all that lubricating. You might consider addatives....But this will probably set off a whole new debate!

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