Yanmar 2gm20 issues (smoke and more)

[OP30]

I've spent some time trying to research my problems via existing threads, but haven't managed to pinpoint the issue(s). I could use a bit of help with the diagnostic steps. I am handy / a quick learner but not experienced with engines much less diesels.

Background:

• The boat is a 30ft sailboat with a Yanmar 2gm20, the boat was built in 2007 but the engine is refurbished and likely older. I believe the current engine may have been installed in 2012/2013 during an overhaul of the vessel
• I purchased the boat about 7 months ago and pretty much immediately had to have work done. The sail drive was replaced and the injectors were determined to be bad and were also replaced. I have also upgraded the alternator and starter and replaced the primary and secondary fuel filters / housings and some of the fuel lines
• The engine ran pretty shakily prior to the replacement of the injector and better after, but never seemed to run well there has always been a little smoke here or there (I can't be certain what color, I'd say grey, sometimes black)
• I have since put a couple hundred miles on the boat, most of which were under sail with the engine used to charge the batteries (running boat computer, instruments and autopilot)
• The smoke seems to have gotten a little worse over time but the engine has run about the same, fairly reliably

Current issue:

• Prior to my last passage the engine was having a little harder time starting and I was getting a bit more smoke (grey / black I think), but I chalked some of this up to cold temperatures (close to freezing)
• During this passage the engine worked for charging but seemed to run a bit differently as it would struggle to gain RPM and then all of a sudden race after some time / once I got the throttle far enough open. I've always had some weird throttle response as the charging load would come on (the LiFePO4 bank and can be quite a load) I've played with the external regulator to try to derate / tune the load so there's not a long term baseline as I keep tweaking it
• I experienced some rough weather on this trip and after a bit of damage (steering) diverted to a closer port and ended up motoring a significant part of the way in. The last 6 or so hours I was running the engine fairly slowly as I needed to wait for high tide and by the time I was waiting at the channel entrance the engine was sounding quite rough and it started smoking a fair bit. I experimented with the whole throttle range in and out of neutral and it didn't get better so I decided to just baby it until I was safely in
• I have found a lot of black residue on the transom of the boat
• It now has trouble starting for the first time of the day but after running for a bit seems to restart okay
• The engine puts out a lot of smoke when first starting and runs very rough until it reaches moderate RPM
• It seems to smoke most when increasing throttle and than will settle down a bit at a given level
• Since dockside testing I have noticed that there is an intermittent ticking that I can hear and it seems like I can trigger it by increasing the throttle. It is more rapid / frequent at higher RPM steady state

What I've tried:

• I've run the engine at different RPM including full open, both in neutral and in forward and reverse
• I changed the primary fuel filter and have run it for a bit with no noticeable change
• I ran the engine and opened the compression levers one at a time, consistently it runs worse on one of the cylinders and in one test the engine ran on one and then stalled on the other
• I ran the engine with the air filter off and at one point there was a sort of belch of black soot (?) that came out the air intake

I've gathered some of the easier ideas that I might try (check crankcase breather, oil change, fuel water treatment, injector cleaner additive, re-bleed fuel lines), but I'm guessing that these may not be enough. I'm also working on getting in touch with a technician, but the further I can get on my own the better.

Any advice on how to rule in or out some of the more involved issues? After some of the basic I'm not sure where to start with things like fuel timing, injectors, valves, compression and the rest...

Thanks,
OP

 

[Bilgediver]

I would suggest checking the tappet clearances as reduced clearances will result in some of your symptoms.

 

[Dan Tribe]

I had similar problems with my 2GM. Eventually traced it to a corroded and porous cylinder head. Probable original cause was a corroded exhaust injection elbow allowing cooling water to enter the manifold.
This may not be your cause but it's fairly simple to check.

 

[jamie N]

Welcome. You've set yourself up to do a good fault find, and all I'd say that when you do the oil change, to pay attention to the 'mag-plug', which if it's 'making metal' could indicate a ring failing.
Very good luck, but perhaps the 1st thing might be to get a compression check, which'd narrow the direction of inquiry a bit?

 

[earlybird]

The 2GM20 isn't the smoothest of engines, esp. at low revs. If yours starts in near freezing temperatures, even with a touch of reluctance, it can't be all bad, GM's don't really like the cold.
A couple of simple actions that I'd suggest before doing anything more serious ; take the exhaust elbow off to check for carbon blockage and possible corrosion of the inner section, then take the boat out and run the engine at near full power for 20- 30 minutes, (an Italian tune-up ) .

 

[HTS]

I had similar problems with my 2GM. Eventually traced it to a corroded and porous cylinder head. Probable original cause was a corroded exhaust injection elbow allowing cooling water to enter the manifold.
This may not be your cause but it's fairly simple to check.

same issue.....in the end replaced it with a 20hp BETA and never looked back

 

[dansaskip]

As others have said first check the exhaust elbow not only do they corrode- a well know fault but they also choke up with carbon as Earlybird has said. Easy and quick to check. If it is corroded inside then replace with a SS one - cheap source from USA - cheaper and better than original. Of course it may not be that but it is a good starting point. If it really is from 2012/13 that is not that old.

 

[jwfrary]

Quick and dirty compression check which is tricky on gm due to a lack of glow plugs.

get your starter handle hopefully kicking around on the boat somewhere and turn the engine you may be able to detect poor compression on one cylinder like this.

if they are both the same then your looking at a fuel issue if not then your looking at loss of compression issues.

the parts are actually not that bad, and they are fairly easy to disassemble.

have a look at Parts4Engines for pattern parts Parts for Perkins, Volvo Penta and Yanmar Engines

no connection, other than I have bought from them quite a bit.

Your black smoke is from overloading. So if your engine is running poorly then it takes less to get the smoke.

the exhaust elbow is the place to start for sure!

 

[jwfrary]

Welcome. You've set yourself up to do a good fault find, and all I'd say that when you do the oil change, to pay attention to the 'mag-plug', which if it's 'making metal' could indicate a ring failing.
Very good luck, but perhaps the 1st thing might be to get a compression check, which'd narrow the direction of inquiry a bit?

no mag plug on a GM incidentally there’s no sump plug! You have to suck it out the dipstick hole.

 

[jwfrary]

PM and ill happily share the workshop manual, should you not be able to locate it online.

 

[Dan Tribe]

Quote "The 2GM20 isn't the smoothest of engines, esp. at low revs."

I started my old 2GM while waiting for a Dutch lock to open. The crew on next door motorboat all started dancing to the beat.
I think they were taking the Mickey!

 

[OP30]

Thank you all!

Valve clearance: I worked my way through the shop manual and made a small adjustment to the clearance on one of the valves on cylinder 1 it was a bit larger than spec, the others seem good as far a I can tell. Maybe a slight improvement in how it runs, but starting was still a 5-6 attempt process. It's 80F where I am now so I'm not sure I have the same temperature excuse...

I completed the oil (and filter) change after a little warmup and then ran the engine in neutral with a little throttle for 5 min. I've also added a little Clear-Diesel to the fuel. I didn't notice metal in the oil but I can't say with too much certainty.

Overall I think some slight improvement but I can't tell for sure if I've got both cylinders running the same. I played around with the compression levers again but it wasn't conclusive as I don't have a good feel for how much throttle to give. The engine will pretty much stall if either cylinder has the lever open for too long. Still getting a fair bit of smoke on startup and when increasing the throttle. I still seem to be getting the clicking at / close to full throttle, but not much in the midrange.

After checking back on this thread, I opened up the exhaust elbow. Well actually I don't think mine is stock as it is not the inverted "U", it just turns 45 degrees down towards the riser. Inside there's a ring of buildup but there doesn't appear to be a full blockage, maybe only 5-15% reduction in area. There doesn't appear to be much corrosion inside the elbow or cylinder head, but maybe it's hiding under the cake. Can I just clean this up? I'll have to look around the forum for more on that.

On second thought I'm a bit skeptical of this mixing elbow as the raw water appears to enter right near the flange / entrance to cylinder head and from the top. Is it just exhaust pressure that would keep it from entering the cylinder head? Is this questionable?

I'm hoping that I don't have a porous head or something that would make it hard to get proper compression. I will try to feel as I hand turn the engine. Will have to see if I can get a proper compression test around here.

Thanks again, hoping I can get to a place were I can rely on it to kick off that dancing beat!

 

[jwfrary]

Thank you all!

Valve clearance: I worked my way through the shop manual and made a small adjustment to the clearance on one of the valves on cylinder 1 it was a bit larger than spec, the others seem good as far a I can tell. Maybe a slight improvement in how it runs, but starting was still a 5-6 attempt process. It's 80F where I am now so I'm not sure I have the same temperature excuse...

I completed the oil (and filter) change after a little warmup and then ran the engine in neutral with a little throttle for 5 min. I've also added a little Clear-Diesel to the fuel. I didn't notice metal in the oil but I can't say with too much certainty.

Overall I think some slight improvement but I can't tell for sure if I've got both cylinders running the same. I played around with the compression levers again but it wasn't conclusive as I don't have a good feel for how much throttle to give. The engine will pretty much stall if either cylinder has the lever open for too long. Still getting a fair bit of smoke on startup and when increasing the throttle. I still seem to be getting the clicking at / close to full throttle, but not much in the midrange.

After checking back on this thread, I opened up the exhaust elbow. Well actually I don't think mine is stock as it is not the inverted "U", it just turns 45 degrees down towards the riser. Inside there's a ring of buildup but there doesn't appear to be a full blockage, maybe only 5-15% reduction in area. There doesn't appear to be much corrosion inside the elbow or cylinder head, but maybe it's hiding under the cake. Can I just clean this up? I'll have to look around the forum for more on that.

On second thought I'm a bit skeptical of this mixing elbow as the raw water appears to enter right near the flange / entrance to cylinder head and from the top. Is it just exhaust pressure that would keep it from entering the cylinder head? Is this questionable?

I'm hoping that I don't have a porous head or something that would make it hard to get proper compression. I will try to feel as I hand turn the engine. Will have to see if I can get a proper compression test around here.

Thanks again, hoping I can get to a place were I can rely on it to kick off that dancing beat!

what you have is a standard elbow. And they aren’t great and a very common source of problems.

incidentally what size alternator have you fitted.

a bit of smoke on acceleration would be normal. If it’s clear when your running normally and the engine is warm you haven’t much to worry about.

 

[jwfrary]

On the exhaust elbow there should be an inner sleeve that stops the water entering the cylinder. If you can see the hole on the inside of the elbow it’s missing!

 

[vas]

no mag plug on a GM incidentally there’s no sump plug! You have to suck it out the dipstick hole.

my 2GMF definitely has a plug on the sump (and it's bloody leaking a bit...) Is that an improvement on the 20 not to have one?

 

[QBhoy]

I’d be back at those injectors. Valve Clarence a good call too. Other than that...run her hard often to keep her in good form too. Be tempted to run a bit of 2 stroke through her too. Good for a number of reasons. Injector cleaning can be one of them

 

[QBhoy]

Also may have missed you saying so...but did you change the oil recently too ? Poor oil condition can reduce compression for sure.

 

[jwfrary]

my 2GMF definitely has a plug on the sump (and it's bloody leaking a bit...) Is that an improvement on the 20 not to have one?

Indeed so called progress

 

[OP30]

My mistake / lack of understanding on the elbow. I took it back apart and determined the jacket is still intact. Makes more sense now.

The alternator is a Balmar XT with an external regulator. I have a shutoff switch (and delayed start) on the regulator so I haven't been starting or testing the engine with the alternator charging,

I did change the oil today, but I plan to give it another one after running it a bit.

I'm going to go through the shop manual and see what service I can do on the injectors / pumps and then see if I can get a real compression test (I couldn't tell much from turning it by hand). I get dark smoke on startup and Idle which makes me think there's a fuel issue or one cylinder isn't happy there. The smoke thins and gets lighter once it's running at moderate RPM and the engine sounds alright, makes me think that both cylinders are doing okay in normal operating range. I still get a clicking sound that intensifies close to full throttle. I've read this could be the injectors (a "wet" injector), hoping they're not too bad. I plan to run the injector additive through now.

Maybe I'm back in the land of "it runs so don't worry". I'll probably keep tinkering...

Thanks everyone!

 

[OP30]

As a minor confirmation, is it normal for the engine to be slow to start after opening the exhaust elbow? And corollary, is it normal that the water is slow coming out the tailpipe? I'm guessing maybe yes, as opening that would equalize any pressure (compression? lifting water through the riser?)...