Yanmar 2GM20 suddenly smokes and quits???

[Sailorman Ed]

I was leaving the Bahamas and switching from my SB engine to my port 2GM20 when after 5 min, I notice it struggling, look at the exhaust and it is spewing unburnt fuel/ dark smoke and suddenly quits. It will not fire again. The boat was already moving so there was not a big load and I had let it warm up before engaging forward. Switched back to the SB engine and no issues. The port engine had started normally.
About 1000 hours on the engine, had just changed the oil and filter (both engines)- checked oil level and correct, valve clearance is correct, loosened the fuel return bolts and fuel comes out, fuel tank full. I can hear the saildrive prop spinning so I know that is not the issue.
Engine turns over readily with the starter, just will not run. Had not had any problems prior to this.

A wide cat so difficult to maneuver with only 1 engine. Came very, very close to hitting a bridge today. What could be the matter?

[Diesel Bill]

Sounds like an air blockage. Black smoke equals unburned fuel, so getting fuel. Any chance it sucked a rag into the air intake? Look for a collapsed air filter or such.

[svHyLyte]

Originally Posted by Sailorman Ed

I was leaving the Bahamas and switching from my SB engine to my port 2GM20 when after 5 min, I notice it struggling, look at the exhaust and it is spewing unburnt fuel/ dark smoke and suddenly quits. It will not fire again. The boat was already moving so there was not a big load and I had let it warm up before engaging forward. Switched back to the SB engine and no issues. The port engine had started normally.
About 1000 hours on the engine, had just changed the oil and filter (both engines)- checked oil level and correct, valve clearance is correct, loosened the fuel return bolts and fuel comes out, fuel tank full. I can hear the saildrive prop spinning so I know that is not the issue.
Engine turns over readily with the starter, just will not run. Had not had any problems prior to this.

A wide cat so difficult to maneuver with only 1 engine. Came very, very close to hitting a bridge today. What could be the matter?

By bets on a blown injection nozzle tip...

BTDT...

[Sailorman Ed]

Thanks both for 2 ideas I had not considered. Intake is easy and I can readily check. Will spray some penatrating oil on the injector to be able to pull it out. What do I look for once it is out?
Ed

[Wotname]

Just remember that your diesel engine only requires three things to start.
Air
Clean Fuel
Good Compression

As for the injector, it should "look" clean and undamaged. Normally you would connect it to the HP pump and observe the spray pattern. It should be conical and even. If it is so bad to stop the engine, the damage should be obvious to the eye. If you try this, be very cautious not to get any part of your body (hand, fingers etc) anywhere near the spray as the pressure is enough to penetrate your skin.

A simpler way to test would be to swap them with the other engine.

However, I find it hard to believe both injectors would fail together unless one was really bad and now the other one quit. Before pulling them I would try to start the engine on one cylinder only and then the other cylinder. Do this by operating the decompression lever (one at a time). If one cylinder fires, it will be rough but will help to point you to the faulty cylinder.

[fwilmeth]

Had a similar problem with a 2GM20 in a monohull. Might check the exhaust coupling (goose neck) located at the rear of the head. Held on by three bolts. It clogs. Especially in salt water. Causes back pressure which relates to engine unable to start. It's a common problem on these engines and is considered an annual maintenance issue.

[ballvalve]

I had a similar issue with black smoke and would not rev at all, i tried all the usual stuff, air filter, fuel filter, diesel from another external tank etc I was just about to pull out the injector when a volvo engineer said its probably your exhaust, i dismissed this as unlikely and carried on, should have listened it was a blocked exhaust elbow

[Christopherlour]

My cousin had the same problem and payed for the cylinder head to be removed. It was in fact carbon buildup in the exhaust.

[a64pilot]

If issue with injector is not visually obvious, you can connect them to the lines and turn the engine over and observe spray pattern, of course it's high pressure so don't hold it in your hand or let the spray contact you.
They should spray of course, not stream. I didn't think injector, but I think it would likely cause your problem, but more likely clogged exhaust elbow, just never heard one get so bad it shut down though

[Sailorman Ed]

Air cleaner was fine, and I tired the compression release for both cylinders no change. I did notice pressure coming OUT of the intake. After checking in with customs, we stopped at Pro Marine in Cocoa who gave me several suggestions to check which I will do this morning:

1. check for a stuck valve
2. check exhaust elbow
3. possible blown head gasket

thanks again for all the suggestions.

[dlockhart]

Mixing elbow on exhast manifold is most likely plugged. Don't use ether or starting fluid whatever you do, the result will be a broken top ring land on one or both of the pistons.

[Sailorman Ed]

OK, not a stuck valve and we can feel air being forced out the exhaust so the elbow is not plugged, I think we are down to a blown head gasket.
Anyone replaced a head gasket? How much work is it?
Ed

[SailsTeam]

Originally Posted by Sailorman Ed

OK, not a stuck valve and we can feel air being forced out the exhaust so the elbow is not plugged, I think we are down to a blown head gasket.
Anyone replaced a head gasket? How much work is it?
Ed

It depends how easy your engine access is. If the engine is completely out of the boat already it only takes a few minutes to remove the head and injectors. How much time do you think it takes to assemble it at the factory? I doubt its more than an hour. Do you have air tools? Hand tools take 5x as long to do things.

[Wotname]

Originally Posted by Sailorman Ed

OK, not a stuck valve and we can feel air being forced out the exhaust so the elbow is not plugged, I think we are down to a blown head gasket.
Anyone replaced a head gasket? How much work is it?
Ed

Feeling air coming out the exhaust does not rule out the possibility of a fouled exhaust. This is common fault with the 2GM20 but normally it does not cause the engine to quit suddenly. With a 1000 hours, the exhaust elbow should have removed and cleaned once or twice already. Now might be a good time .

It has to come off to replace the head gasket anyway so do that first - just in case it is the only problem.

Replacing the head gasket is simple job if you know what you are doing. Maybe an hour plus for someone who does it for a living and has reasonable access.

Maybe a full morning for someone who is very mechanical and doesn't have to go looking for tools.

All day for someone who hasn't much experience with engines but is still good with tools.

And some folk shouldn't even attempt it

You will need a deep walled socket (17mm IIRC). I can check the size later if you like.

The injectors don't need removing which is good because sometimes they are a pain to get out. Of course the fuel lines to them need to be removed.

[Sailorman Ed]

got the elbow off, not spotless but certainly not plugged.
Really looks like head gasket now. Got 2 places to call in the morning to see if either has the gasket and can help be get it replaced.
thanks again to all the suggestions.
Ed