2GM Yanmar Oil in Exhaust

[miabellabrian]

PLEASE HELP! I have blue smoke now turned into oil/or diesel coming out the exhaust and floating on the water, even at low revs. Still starts and idels ok.This has all just happened today after pushing the engine a little, perhaps I have blown the rings??? .

It is a 10 year old Yanmar 2gm (with a heat exchanger fitted many years ago) in my 25 foot yacht, I had the engine running well, a little warm at revs over 2300 rpm, I suspect that is has an over size prop fitted, as I can push 9 knots at 2200rpm. also can rev higher in reverse ( as lower gearing I believe)
How can I test what is happening with the oil or diesel coming out the exhaust.
Could it be rings, or perhaps head gasket only?? or valve seals?? how do I test, before having to do a big rebuild

please help
cheers
brian

[Raythesailor]

Hi Brian,
I am sure you will soon receive lots of good advice from engineers on here.

It just strikes me that 2300RPM, and 9Kn is excessive in a 25ft yacht.

I have a 45 ft and cruise under engine at1500 RPM at around 6Kn. From time to time I give it a burst of power for a few secs

Good luck and fair winds

[Wotname]

Is the prop clean???
Is the bottom clean (ish)?
What RPM could you get previously with WOT and what RPM can you get now? With clean hull and clean prop, you should be getting 3400 to 3600 RPM.
How many hours on engine?

My guess is that rings will be OK and so will gasket, something external is loading the engine. Mind you, just a guess at this stage.

How long have you been getting blue smoke?
9 kts seems awfully fast, have you verified this?

Sorry for so many questions but the answers will paint a more accurate picture of what is happening with your engine!

[miabellabrian]

Problem started today, I have blue smoke/ oil coming out, not too worried about the prop size or RPM at the moment, as I can change the prop when I take it out of the water.

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[miabellabrian]

Worried about the oil coming out and perhaps the engine blowing up

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[Wotname]

Does it start easily? If yes, then rings are probably fine.

These engines rarely if ever "blow up" !

Is your low oil pressure alarm working, ie does it sound prior to starting?
Is the oil OK, ie correct quantity and NOT thin?

Knowing the RPM previously at WOT with clean hull and prop and comparing it to now is an extremely good diagnostic tool to help solve your current problem!

[Dulcesuenos]

Originally Posted by Raythesailor

Hi Brian,
I am sure you will soon receive lots of good advice from engineers on here.

It just strikes me that 2300RPM, and 9Kn is excessive in a 25ft yacht.

I have a 45 ft and cruise under engine at1500 RPM at around 6Kn. From time to time I give it a burst of power for a few secs

Good luck and fair winds

The 2gm20's are a 3600 rpm engine if it's been propped wrong and run excessively at 50-60% of its max rpm there could a lot of issues. It may just be unburned fuel in the exhaust looking like oil then again,,,


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[Sailmonkey]

By "oil" do you mean black globs floating on the water?

If so it's not oil......it's carbon......and you're severely over propped or you have a prop covered in barnacles.

Also double check that 9 knots. What sort of hull is this?
Edit: a contessa 25 is not going 9 knots


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[captstu]

Are you using oil? Worse, is your engine's oil level rising?

IF YOU over prop, unturned fuel can leak back into the engine oil -a disaster in the making.

[Celestialsailor]

I'd like to ask 1) How many hours a go was the oil changed?
2) Are you loosing oil in the crank (dip stick)?
3) Do your gauges work? What do they say (Temp and oil pressure)?

[seasick]

Blue Smoke
Blue exhaust smoke indicates that oil is burning during the combustion process. Look for a condition that allows oil to enter the combustion chamber, such as a broken pis- ton, broken or stuck piston rings, a damaged cylinder wall, worn valves or guides, a defective crankcase vent, or an overfilled oil sump.

Start with overfilled oil sump, then defective crankcase vent. If not these, then, it's time to dig deeper.
Here's the shop manual: http://www.kb-kbh.dk/shipslib/motore...hop_manual.pdf

[Raythesailor]

Originally Posted by Sailmonkey

By "oil" do you mean black globs floating on the water?

If so it's not oil......it's carbon......and you're severely over propped or you have a prop covered in barnacles.

Also double check that 9 knots. What sort of hull is this?
Edit: a contessa 25 is not going 9 knots


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I think you are correct.
Black globules floating on the water from the exhaust are normal excess carbon\soot.. This is why I believe a few secs of excess power is good good to blow out.

A 25 ft yacht should be incapable of 9 Knt unless a flat bottom planning hull, or measured on G P S with current behind. SOG.

[GrahamHO]

Originally Posted by miabellabrian

PLEASE HELP! I have blue smoke now turned into oil/or diesel coming out the exhaust and floating on the water, even at low revs. Still starts and idels ok.This has all just happened today after pushing the engine a little, perhaps I have blown the rings??? .

It is a 10 year old Yanmar 2gm (with a heat exchanger fitted many years ago) in my 25 foot yacht, I had the engine running well, a little warm at revs over 2300 rpm, I suspect that is has an over size prop fitted, as I can push 9 knots at 2200rpm. also can rev higher in reverse ( as lower gearing I believe)
How can I test what is happening with the oil or diesel coming out the exhaust.
Could it be rings, or perhaps head gasket only?? or valve seals?? how do I test, before having to do a big rebuild

please help
cheers
brian

9 knots at 2200 with a 2GM in 25' is a World record. Firstly contact Guiness to claim the record. Unless you are on the Salt Lake at Bonneville. Perhaps your GPS is set to kilometres / hour which will be approx 4.5 knots and more like it.


Next have a compression check. They require a special diesel compression gauge as the 2GM is 22:1. You can't use a gauge for a car engine which is usually around 9.5 :1. You might find one cylinder is much lower in compression than the other. A new engine will read around 400 psi.
Then you remove the head and get it checked for flatness and / or blown head gasket. I do suspect rings or piston problems. Been there.
Then you might have to pay a lot of money or buy an outboard.

[01kiwijohn]

Slow up there. Could be only the result of prolonged, previous running at less than designed loads. I run my 3GM30 at WOT for about 5 mins every time I take it out. It blows some blue smoke for a minute or so, then settles down.
9 knots? Contessa 25?? Probably not happening. Check with GPS.
For correct pitch, Yanmar usually suggest (taken from their Installation Manual) 1) Run at max idle, record that speed. 2GM 20 spec. is 3800 to 3850. 2)run boat at max throttle and engine speed should be between no load max RPM and Rated output speed; ie; 3600 and 3800 for the 2GM.
Most engines run at about 95% of max output if pitched correctly.
Let me know if that helps

[svthreecheers]

Originally Posted by miabellabrian

PLEASE HELP! I have blue smoke now turned into oil/or diesel coming out the exhaust and floating on the water, even at low revs. Still starts and idels ok.This has all just happened today after pushing the engine a little, perhaps I have blown the rings??? .

It is a 10 year old Yanmar 2gm (with a heat exchanger fitted many years ago) in my 25 foot yacht, I had the engine running well, a little warm at revs over 2300 rpm, I suspect that is has an over size prop fitted, as I can push 9 knots at 2200rpm. also can rev higher in reverse ( as lower gearing I believe)
How can I test what is happening with the oil or diesel coming out the exhaust.
Could it be rings, or perhaps head gasket only?? or valve seals?? how do I test, before having to do a big rebuild

please help
cheers
brian

Hello Brian
Blue smoke means oil being burned in your combustion, would indicate problem
with pistol rings or valves/valve guides / head gasket.
Take a Compression Test, if too low, injected some oil through the hole and
test again.If the pressure stays the same you will have problems with the head
( gasket, valves or guides ) If the pressure increases you can expect trouble
with the oil and compression rings on your piston.
I have a 42 ft displacement hull, 85 hp engine, top speed 7 know.
Wish I could get 9 kn!
Good luck
Cheers
Siggi