Oil from Raw Water Exhaust 2GM20C

[Lambada30]

Hi Everyone,

Need some advice. I have a Yanmar 2GM20C fitted on a 30ft. Yesterday I motored for 7 hours at around 2000rpm (5kts). Engine ran fine until I dropped the rpm upon berthing and noticed an oil slick. I thought it might have just been a build up of diesel so I didn’t think much of it. Returned the next day. Engine started fine and runs fine however, it is expelling what appears to be engine oil. The dipstick has dropped as well.

A bit about the engine: it should cruise at far higher RPM than I cruise at, however, I’ve found that anything over 2000rpm the engine dislikes and overheats. I have checked the accuracy of the rpm count and it is almost spot on. I recently replaced oil, oil filter and impeller. Engine has done 1500hours but is almost as old as the boat. The last owner changed the prop but allegedly this was done by a professional.

Any advice is greatly appreciated! I’ve attached some photos of the expelled raw water.

[Lambada30]

An update, after running the engine the dipstick has definitely dropped.

[Lambada30]

Any help appreciate.

[Sailmonkey]

Is this engine raw water cooled or does it have a heat exchanger?

Is there an oil cooler anywhere in it?

Does it idle smoothly?

Is it able to reach full rated rpm in gear (never mind the overheat, just for a short duration)?

[gonesail]

maybe not the problem but have you replaced the exhaust elbow lately?

[deblen]

Oil seal leak in RW pump?


http://j30.us/files/YanmarGM&HMWorkshopManual.pdfYanmar RW pump.PNG Views: 242 Size: 122.6 KB ID: 184730" style="margin: 2px" />

[Cheechako]

Originally Posted by Lambada30

Hi Everyone,

Need some advice. I have a Yanmar 2GM20C fitted on a 30ft. Yesterday I motored for 7 hours at around 2000rpm (5kts). Engine ran fine until I dropped the rpm upon berthing and noticed an oil slick. I thought it might have just been a build up of diesel so I didn’t think much of it. Returned the next day. Engine started fine and runs fine however, it is expelling what appears to be engine oil. The dipstick has dropped as well.

A bit about the engine: it should cruise at far higher RPM than I cruise at, however, I’ve found that anything over 2000rpm the engine dislikes and overheats. I have checked the accuracy of the rpm count and it is almost spot on. I recently replaced oil, oil filter and impeller. Engine has done 1500hours but is almost as old as the boat. The last owner changed the prop but allegedly this was done by a professional.

Any advice is greatly appreciated! I’ve attached some photos of the expelled raw water.Attachment 184712

That looks pretty bad. I was going to suggest a bad injector spewing fuel, but that is engine oil for sure.
Not likely related ...but what is the max rpm the engine will reach with your prop? It sounds like it may be overheating due to overload and being over pitched prop.

I think Deblen may have found it for you.

[Siberian Sea]

If engine had an oil cooler and this cooler had raw seawater flowing through it it would be possible that if one of the internal cells or tubes started to leak the higher oil pressure would force oil into the raw seawater side and you would notice oil out exhaust and a drop in crankcase oil level.

[Sailmonkey]

Originally Posted by deblen

Oil seal leak in RW pump?


http://j30.us/files/YanmarGM&HMWorkshopManual.pdfAttachment 184730

I'm pretty sure the GM series engines were all belt driven water pumps. (actually just looked up the 2gm20C, it has a belt driven pump, and it is raw water cooled).

Being raw water cooled, I fear that an oil gallery in the head has been breached by seawater (i'm hopefully wrong).

EDIT......now that I dig deeper, deblen is probably correct!! too many 2gm variants!!

[Bill Seal]

If it has internal oil passages to the head, it might (if he's lucky) be a leaking head gasket. Would also explain the overheating.

[sailorchic34]

Originally Posted by Bill Seal

If it has internal oil passages to the head, it might (if he's lucky) be a leaking head gasket. Would also explain the overheating.

^^^^THIS. 85% it's a blown head gasket. Note oil can leak from the push rod passages as they is how the oil drains back to the crankcase. Cheap and easy fix.

Another option is broken rings (not cheap at all). Some 1994 vintage yanmars had bad ring lands on the pistons, which could cause the rings to break on one or more pistons. However, this would make it hard to start and have high crank case pressure. If you remove the oil fill cap with the engine idleing and you get lots of grey smoke then it's rings. Don't ask how I know..... I have personally touched every piece of my yanmar...

It is not the raw water pump or discharge elbow. Yanmar 2&3GM's are Belt drive raw water. 1GM's are gear drive raw water..

For oil in exhaust and overheating or running hot it's more then likely a head gasket.

Worst case it's a cracked block, but let's not go there.

[NYSail]

Originally Posted by Siberian Sea

If engine had an oil cooler and this cooler had raw seawater flowing through it it would be possible that if one of the internal cells or tubes started to leak the higher oil pressure would force oil into the raw seawater side and you would notice oil out exhaust and a drop in crankcase oil level.

Typically what I have always seen is yanmar oil coolers are pipes into the anti freeze loop.

Greg

[NorthCoastJoe]

I would second the blown head gasket. Oil is fed to the head via an external tube and drains back through the push rod holes. I recently tore down a 2gm and the raw water passages were completely blocked in several areas. The reason for the teardown was the head gasket was blown.
Pull the head and spend some time cleaning the passages, also check the block for built up crud. If it is as old as the boat and never been done it is long past due. Also inspect the exhaust elbow the tends to erode at the discharge side of the baffle. One end of the riser is left threaded. There is a free downloadable manual for this engine.

http://j30.us/files/YanmarGM&HMWorkshopManual.pdf

[Lambada30]

Hi all,

Thanks very much. Is it hard to replace the head gasket? Is there any damage I can do by trying to do this?

Someone at the club suggested that if it was the head gasket the engine shouldn’t be able to start... or would be hard to start. However, mine starts fine... is this right?

[blueazimuth]

Before tearing the engine down, eliminate the small ticket items, and consider the following:
Your symptoms suggest you may have two problems, one of which could be engine blow by. Or a previous owner had blow by. But, at 1500 hours, and if the hour meter hasn’t been changed, or tampered with, blow by seems unlikely.
1. Was the oil level correct before the prop was changed?
2. Ask the previous owner (judiciously) why he changed props. There had to be a reason, valid or otherwise.
3. Did engine ran up to speed, and run cool, before the prop was changed?
4. Does he still have the old prop, or at least knows diameter, pitch and number of blades?
5. ehat is the size, pitch and blade number of prop now on your boat?
6. What is contact number of professional who changed prop?
Note: Work done by a “professional” is always suspect. In some countries, if a guy sees his first Volvo on Tuesday morning, and gets Kinko cards printed up on Tuesday afternoon, then he’s a Volvo expert on Wednesday morning. Even somebody from a respected shop can BS his way in as an expert, or he may be a shop trainee. Before letting anybody work on my boat, I always ask for a card. No card could be innocence, or a red flag. Ask me how I know. Be with the mechanic throughout the work. Listen carefully to what he says. Make notes after he leaves. This could be a big ticket item, and making notes seems common sence. If you are out of town, never have anyone (except a competent and trusted friend) to even go aboard your boat. Yep, I’m cynical. Ask me why.
2. Carefully check the underside of sump gasket, and transmission to engine gasket, for oil leaks. In some older engines, like Volvo MD series, the transmission oil was common to the engine and often leaked.
3. Wipe with paper towels, then clean with a solvent soaked rag. When scrupulously clean, top up with oil, run the engine under load, and up to temperature. Re check for leaks using a paper towel. The oil cooler, if there is one, may also be leaking.
4. Leaks show part of the problem. In this case, probably not all. But if the engine has to be pulled, you will know that the lower gaskets have to be replaced.
5. If no leaks, and even with leaks, it looks as if you could have any of a number of problems.
6. Other posts have made good suggestions to keep in mind, but at this stage, you need a trusted friend and / or a competent, experienced mechanic. Ask him for 2 references, and check them out. Non checkable references aren’t references. They are another red flag. Get a second, even a third opinion.
7. Good luck