2GM Yanmar Oil in Exhaust

[Wotname]

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

Brian, let me try to help you one more time and please believe I'm taking the time to post to try and help you rather than any other reason.
First let's have a look at the inconsistent data you have provided.

The engine is apparently 10 years old so that means a 2005 build. I can't recall when the 2GM ceased production but it was in the 1980s or early 1990s. So I supposing it is really a 2GM20 or it is the original engine in your 1985 boat which makes it 30 years old. I'm sure you appreciate there is a considerable difference between giving advice about a 30 year old engine compared to a relativity young 10 year old one. So it would be really helpful to know the number of hours on it.

Next you say you are running fairly hard at 2200 to 2300 rpm. I assure you this is not running it hard. This engine (either 2GM or 2GM20) will run 24/7 at 3000 rpm, in fact it will love you for it.

Now it is possible that you can only get 2300 rpm at WOT but that really does mean there is a significant problem. Usually the problem is a badly fouled prop or bottom or both BUT while I somewhat doubt the 9 kts claim, I KNOW you can't get 9 kts with a badly fouled bottom in a 25 ft displacement boat so I assume the bottom is reasonably clean.
If the engine was extremely worn or had stuffed rings, maybe that would explain the low rpms but if the rings were that bad, it wouldn't start without lots and lots on encouragement. You say it starts and idles OK, so that rules out stuffed rings. This engine needs good compression to start especially when cold. If it starts easily, the compression is OK.

You say the issue happened in a hour or so of hard running but I repeat, 2300 rpm is not hard.

So what has caused the problem. Valve guides don't just go from good to bad in one hour and they would have to be seriously bad to give your symptoms.

I really think the answer lies in many of the previous good suggestions given others in this thread, most of whom know more about diesel engines than myself.

The clogged exhaust elbow is a potential area to look at. These can go from good to bad in a nanosecond. A failed fuel pump diaghram might be a problem by letting diesel into the sump and so thinning the oil allowing it to pass by partially worn rings.

But really to help you properly (as you have requested), you should go back and answer each and EVERY question posed by the various respondents. IT IS UNLIKELY to be suddenly broken rings, head gasket or valve guides however if you insist that these items should be checked FIRST, then your only option is to find the local DIESEL mechanic and get a compression test done or a leak down test.

But do remember the members who have taken the time to post questions about RPMs and hull et al have many many years of boat engine experience behind them. In fact some of them will have forgotten more than I will ever know.

EDIT. Perhaps you made a typo in your OP, perhaps you meant 3200 rpm rather than 2300???? If so that changes things somewhat but not a lot. In fact the symtons you described could be a result of the engine running atbit designed rpm (3200) and thus cleaning out all the accumulated carbon from prevoius slow running. The carbon and diesel mix looks EXACTLY like oil in the water. If starts OK, sounds OK and you have good oil and good oil pressure, take it for another run!

[hamburking]

Originally Posted by Blue Crab

The 9 kts has a simple explanation: he sails in upsidedownland. It's 6 on the correct side of the equator.

Or he's going 9km/h, which is a more likely speed for a 25' sailboat at WOT (4.8 knots).

[Blue Crab]

Same engine here. I'm on the edge of my armchair. No, really.

It's all I can do to goose it past 3k rpm since at 3150 the boat gets up on its double foils and clocks in at 15 kts. I do this mostly in no wake zones as on the foils produces virtually no wake. At WOT I become airborne but as the rear foil is no longer in the water the RM AP doesn't function. This means I have to physically get on deck and steer with sailpower. And you think you've got troubles?

[Geitz]

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
brian

If you haven't already done so, check the air cleaner. Make sure that nothing got sucked in and could be blocking the intake.

This was suggested previously.......Try running up to WOT (wide open throttle, ~3600rpm) for a short time, while in neutral. Do you get the smoke and soot? If no smoke or soot, it suggests that the engine is overloaded by a dirty, fouled or too large a prop.

[Ribbit]

Had a lot of smoke out of a new engine (just pulling away from its first service) - a petrol engine though, so the smoke was white.

At the service, they had put the oil in for the model with the bigger engine, which held a lot more oil.

Too much oil blew the valve seals (and who knows what else). So as you guys have pretty much covered everything else that's likely wrong, there's not way too much engine oil in the thing is there?

With the diesel being injected into the leaked in engine oil in the combustion chamber, could the smoke then be blue as a result?

Certainly need to know what the oil level is on the dipstick etc., though.

[Cheechako]

"You say the issue happened in a hour or so of hard running but I repeat, 2300 rpm is not hard."
Great post overall, but iIn my book, if it's propped to max out at 2300 rpm, it IS being run hard. An engine doesn't have to be run fast to worked hard right?

[Cadence]

Originally Posted by Cheechako

"You say the issue happened in a hour or so of hard running but I repeat, 2300 rpm is not hard."
Great post overall, but iIn my book, if it's propped to max out at 2300 rpm, it IS being run hard. An engine doesn't have to be run fast to worked hard right?

There is a difference between RPM and working hard. Sounds like she is over propped and working hard if he can't make rated RPM. If he could he would be doing 12 knots.

[sailorchic34]

Blue exhaust would be oil. Black exhaust would be overloaded, grey exhaust would be unburnt fuel and white exhaust is water / coolant.

So assuming it is blue smoke and it is oil and not fuel in the water, we can assume one of several things. You have a blow head gasket, quite common. or broken rings or ring lands, less common. Though not uncommon enough for my taste. Both could happen quickly.

It might be bad injectors but that would be grey smoke normally, but it would cause a oil slick on the water.

I also though it might be a rope or plastic wrapped about the prop, but that would generally not put oil in the water and would cause black smoke.

My guess is head gasket as that's the easy thing and would fail quick. Other symptoms of a blown head gasket could be water (grey) in the oil or bubbles in the fresh water tank/heat exchanger. But you don't need a water in the oil or bubble in the tank to be a blown head gasket. Engine would run hotter too.

[GrahamHO]

Originally Posted by Blue Crab

The 9 kts has a simple explanation: he sails in upsidedownland. It's 6 on the correct side of the equator.

If he goes to his GPS and selects Menu / settings / units / speed, and changes Kilometres / hr to Knots it might help.
They are each a "K" sometimes with small letters.

[Wotname]

Originally Posted by Cheechako

"You say the issue happened in a hour or so of hard running but I repeat, 2300 rpm is not hard."
Great post overall, but iIn my book, if it's propped to max out at 2300 rpm, it IS being run hard. An engine doesn't have to be run fast to worked hard right?

Hmm... I'm not sure I agree but then again I might be wrong as I'm not professional diesel fitter or such like .

This how I THINK it works.

The volume of air induced at any particular rpm is fixed by the design of the induction components and can't be altered by the operator.
The volume of fuel injected is controlled by the injector pump(IP) not by the operator.
The only external control is by the power lever often called the throttle or fuel lever. In fact it is neither and is probably best described as a governor or rpm control.

When everything is tickety boo, and you advance this lever to WOT, the governor thinks you want 3600 (for a 2GM20) and asks the IP for enough fuel to get the engine to 3600. Once there, the governor holds that rpm by telling the IP for more or less fuel. Similarly say at half throttle setting, the govenor will attempt to make the engine run at say 2000. Remember the volume of air is fixed at any particular rpm and is known by the IP.

However when something in the load changes, everything gets out of wack. Say thevpropnis fouled, you ask for half throttle (2000) and the governor / IP dumps enough fuel for normal conditions but really the engine needs more power due to fouled prop and so doesn't reach 2000. The governor expects 200 and tells the IP to add more fuel until the engine reaches 2000. However there is only so much range in the IP to add fuel.

Result is that the engine doesn't reach 2000, so the operator advanves the throttle further, now the governorvthinks you want say 2800 and the cycle continues which way too much fuel being dumped into the engine for the amount of fixed air.

This cokes up the cylinders and exhaust system and produces the black smoke as it is operating way too rich.

Is this working the engine too hard, I'm not sure but I do know it isn't good for it

But would anyone seriously overprop a engine to the extent that you could only get 2/3 of available rpm at WOT. I would like to think not.

This is one of the many reasons we need to know the past rpms the OP could get at WOT but until he resurfaces, we are in the dark.

It is a different story if the boat is proped for hull speed at say 2200. This assumes the hull speed can be obtained with say 8 hp and that 8 hp occurs at 2200. Then everything is reasonably sweet although the engine remains lightly loaded and normal operation is conducted at half throttle. This will be OK providing you run the engine up to full power every 2 hours or so. Of course you won't go much faster but the engine will love you for it.

[Geitz]

My boat came from the factory over-propped. I can only reach ~2800 when the black smoke starts. Anyway, if the OP is describing the smoke correctly as "blue", and it appeared suddenly, I'll place my bet on the head gasket.

Sent from my SM-G900V using Cruisers Sailing Forum mobile app

[miabellabrian]

thanks for the advice, it hope it is a blown head gasket and not the rings!

[miabellabrian]

Ok, lets look at the facts again. Firstly I said I thought the boat was over propped from the beginning, and as I have come to learn this can be proven by the fact that it revs higher in reverse than in forward.(lower gearing in reverse).
Also now that you all have had a good laugh at my 9knotts at 2200-2400 rpm, remembering that the prop is too big, the boat is a Contessa 25, an old yacht designed by Peter Cole ( well respected designer of fast yachts in his time), and a reasonable narrow fast design, keeping in mind that im talking about Lake speed, not ocean speed. keeping that in mind I believe I have pushed the engine too hard by pushing more than 2500 with the excessive load of the big prop. As a result the rings are now not sealing right and when removing the oil cap, it looks to the untrained eye like I have Blow By, so I was going to try to put some Malvin Mystery Oil, or transmission oil in the cylinders to see if they will seal again, and check for bubbles in the heat exchanger for a blown head gasket !! how does that sound??

[miabellabrian]

no im talking knots

[miabellabrian]

oil level is good, Im sure Im getting Blow By