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ianmkent

Yanmar 1GM

12 posts in this topic

My Yanmar 1gm was running fine I increased the revs and noticed black colour water and black smoke coming out of the telltail I cut the engine out. And restarted at low revs still had the black stuff I then conected a fresh water tank for cooling but still had the same problem.

I recently brought the boat and the last owner did not use her much and when they did it was only for a few hours at a time. The engine was running fine from Faversham to Rye. Does anyone have any suggestions on fixing the problem.

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black smoke is too much fuel and not enough oxygen. if your temp alarm isn't going off, I wouldn't worry about that. check the air filter, even try running the engine with the air filter off (briefly) to see if it makes any change in the black smoke. if it isn't that, you could have an injector problem.

As an FYI, you should run it up every once in a  while to burn out the carbon. When I do this I get black particulate out of the exhaust for quite a while afterwards, but the black smoke is most likely related to the fuel/air mixture being heavy on the fuel side.

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New injectors solved a lot of problems on my 3gm and were cheap and easy to diy install. I just bought new nozzles for about $60 each, plus the required gasket set.  I also cleaned the pre combustion chamber while I was in there. 

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May have a bad thermostat.

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Check the exhaust elbow.  It may be plugged with carbon/scale causing back pressure and incomplete combustion.  I had the same symptoms and a new exhaust elbow fixed it on my 2GM and this year on my 3YM30.

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7 hours ago, Dabnis2 said:

Dirty or over pitched prop? Did it gradually do that or all of a sudden? Will the engine pull maximum RPM's under load? Any work recently done on the engine?

Thanks for all the replies, it did it all of a sudden.

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We need to take a poll!  All good suggestions on possible causes, but we need to see who is closest.

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I found out from the owner that the fuel had been in the tank for over a year and had not been serviced in there ownership. I really should have serviced her before leaving Faversham for the Solent.

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The exhaust elbow on these don't last that long and the head will have a bunch carbon deposits restricting flow as well. There used to be someone on ebay selling them for $100. To clean the carbon deposits out of the head, it's probably best to pull the head (not hard to do). When cleaning, be careful not to chisel into the water jacket. If you damage the head a new one will be about $400. With head off, you can inspect the cylinder walls and valves which are probably fine. Not related to your issue, but keep an eye on the water pump leaking salt water onto the aluminum oil case cover and corroding it. If it's leaking, pull the pump and replace the seals and possibly the shaft. 

 

 

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11 hours ago, DSE said:

The exhaust elbow on these don't last that long and the head will have a bunch carbon deposits restricting flow as well. There used to be someone on ebay selling them for $100. To clean the carbon deposits out of the head, it's probably best to pull the head (not hard to do). When cleaning, be careful not to chisel into the water jacket. If you damage the head a new one will be about $400. With head off, you can inspect the cylinder walls and valves which are probably fine. Not related to your issue, but keep an eye on the water pump leaking salt water onto the aluminum oil case cover and corroding it. If it's leaking, pull the pump and replace the seals and possibly the shaft. 

 

 

having just been through this, you're right - pulling the head isn't hard at all. However the clearances on the rockers and percussion caps is a royal pita to get right since the adjuster threads are so coarse. Also, don't reassemble if you don't have a torque wrench.

You can get a replacement stainless 1gm10 elbow for $120, which is less than the OEM part. 

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I replaced my 1gm's elbow last month with the stainless one found here, nice guy and ships fast (got it in 2 days): http://exhaustelbow.com

I had the same issue with black water coming out of the exhaust, replacing the elbow fixed it. The inner tube within the elbow corrodes which can send the raw water in through the exhaust port depending on how bad it is. 

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I did my 3GM30F's elbow 2 years ago.  It wouldn't rev, black smoke, etc.  I bought the stainless version mentioned above.Fixed everything.

Just bcz, I cut it open in our machine shop.  This is what it looked like and it all made sense.

Elbow.jpg

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