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Old 12-12-2010, 20:57   #1
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Yanmar 1GM10 Exhaust Elbow and Carbon

Managed to get up to my boat nine hours drive away and do some essential repairs. One of the things I had no spares for but wanted to check was the 1GM10's exhaust elbow. There appears to have been salty water seeping out and also rusting the fuel line underneath. I planned to carefully pull the elbow off even though I had no gasket or replacement elbow as at least then I would know if I needed to get another elbow.



The elbow came off the motor with no problems. I noticed:

(a) There was so much carbon in the exhaust elbow I could not tell if it has internal integrity however, the muffler pipe was so jammed on that I could not take the pipe off the exhaust elbow.

(b) So much carbon buildup in the exhaust hole in the cylinder head that I could not see the exhaust valve that I had read in some forum post that said it would be visible.

(c) Gasket? What gasket? There was none which would explain why there was seepage of salt water.





Now, how do you suggest I proceed?

How do I de-carbon the exhaust port? And does the amount of carbon in pic indicate that it would be best to take the head off and give the whole show a clean?

The face where the cylinder head matches the exhaust elbow has pitting, so will the gasket compensate for this or does more need doing?

Should I replace the fuel line that has rust to be on the safe side or simply wire brush and repaint?

How do I take the elbow off the exhaust hose as it is well and truly stuck on? Should I first loosen the metal band thingy holding it on? [just joking : )]. If I could wiggle the hose I might be able to get it off but my puny muscles made no impact.

Late news: I am now the proud owner of a new aftermarket exhaust elbow from ExhaustElbox.com - Better Than Factory New. The fellow, Ben Cotton, is in the USA but I found his advert on an Australian site, ended up buying via his ebay store and even though I am in Australia the cost including postage was less than half buying an original. Looks well made, heavy stainless steel so I hope it holds up to the heat and salt water.
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Old 13-12-2010, 00:46   #2
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It is easy to sit back and advise someone to do a lot more work than he originally intended. In this case - one of the first things to establish is why the carbon buildup? Are worn rings allowing lubrication oil to be burnt ? Poor injection of diesel so that some diesel is not fully ignited in the combustion chamber?
Whatever, a de-coke and valve grind is on the books. New head gasket,
Although the picture of where the elbow bolts onto the block gives the impression of a gasket. You will need a new one for the new elbow.
To de-carbonize the exhaust port, start with old screw driver, then small hammer and screw driver.
Then a rotary steel wire brush that will fit in the port, attached to an electric drill chuck (wear eye protection)
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Old 13-12-2010, 00:56   #3
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Oh your engine is going to run sooo much better. Your pics are great. New exhaust elbow and gasket to be sure. Very common problem. If you want to play with cleaning the old one for a spare you'll realize that a new one is just easier. Pull the head yourself and have it cleaned an checked and replace it yourself. You could have the compression checked but my guess is that you've been loving this engine to death. Let it run like Yanmar specs say to run it.
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Old 13-12-2010, 01:14   #4
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If you can't find a replacement gasket for the exhaust port, you might measure the red and blue spacing on the bolts. At an automotive parts shop you might be able to find a gasket with 4 bolt holes - just cut off one to fit the 3.
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Old 13-12-2010, 01:56   #5
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This outfit sells Yanmar parts at a reasonable price, here is one with a part that might do the trick
Yanmar Gasket
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Old 13-12-2010, 03:33   #6
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Quote:
Originally Posted by Laidback View Post
In this case - one of the first things to establish is why the carbon buildup? . . . .
Whatever, a de-coke and valve grind is on the books. New head gasket,
. . . .
To de-carbonize the exhaust port, start with old screw driver, then small hammer and screw driver.
Then a rotary steel wire brush that will fit in the port, attached to an electric drill chuck (wear eye protection)
Thanks, Laidback. The boat is new to me so I don't know why the carbon buildup except age, which from what I have read is fairly usual for this model of raw water cooled motor.

Sounds like a plan: ream out the exhaust port and sooner or later, hopefully sooner, get the head off and cleaned up.

Eye protection? I love eye protection! I don't care what I look like or how awkward the protection is to wear, I have had too many instance of flick-ups smacking me eye protection not to wear it.
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Old 13-12-2010, 03:59   #7
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. . . . New exhaust elbow and gasket to be sure. . . . If you want to play with cleaning the old one for a spare you'll realize that a new one is just easier. Pull the head yourself and have it cleaned an checked and replace it yourself. You could have the compression checked but my guess is that you've been loving this engine to death. Let it run like Yanmar specs say to run it.
Good advice, Tellie. Even before pulling off the old elbow, I decided if it was good, keep it otherwise ditch it, get a new one [which I have done]. I wouldn't be relaxed using a patched up old one as it is critical for good operation though I would use a sound condition old one [and carry a spare].

You are the second person to suggest pull the head off and I think it is probably the best thing to do. Being 9 hrs drive away from my boat makes it difficult to pop down there but if I can clean the exhaust port, maybe it will run better so I can more easily bring her down when the wind is in the right direction. Then I can take the head out more easily.

I just got the boat and in the ten hours or so of engine use, I have been loving it but hopefully not to death. First thing I did was replace the aircleaner since it was feeding foam element into the cylinder, not a nice diet. I changed the chewed up water pump rotor and anode along with the fuel filter. The oil was so black and thick I almost had to scrap it out and along with changing the oil filter I have changed the oil twice, yes, twice with the second time after ten hours running. I have had diesel motors before but never seen such aweful oil in a sump.

When the motor first started, which in itself was a drama as the PO had not done the storage thing but the motor sat for 6 months, I could only get 2 knts max out of it. At 2,500 revs the black smoke was so bad I thought if I get a wind shift and it blows back on me I will die of no air.

Cleaning the prop of growth got me 5 knts easy though at 3,000+ revs with load, the black smoke starts to appear again. An instruction note I found left by one of the PO's for the PO before me said that the motor always blows black smoke, that is just the way it is. The note also said how to shut down the motor using the decompression lever which is a big no-no. So, major neglect from various PO's. I am not a perfectionist but I try to reduce risks by keeping equipment operational and that to me means proper maintenance.

I don't know exactly what made the buildup of carbon, but I do know the motor has been neglected and it will be much much better when it is able to breath in and out more easily and the prop is completely polished rather than just having me dive down into the croc-infested murky water where it is moored to bash barnacles off to clean it up a bit. I am looking forward to the time when I don't get anxious everytime I go to start it that it won't go and it is purrs along sweetly, if ever these single cylinders can be said to 'purr'.
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Old 13-12-2010, 05:37   #8
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My local Yanmar stockist reckons that he only sells two parts for Yanmars, filters and exhaust elbows.

True enough, my 4JH3-TE was pretty thick with carbon at 400 hours. Just took it off and rotary wire brushed it, now fine.

My mate in the UK has a 1GM10 on his Hurley 24 and we love it, I swear that it doesn't actually use any diesel at all, after 10 hours of motoring we still couldn't see any change in the tank level.

Duncan
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Old 13-12-2010, 06:42   #9
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I went through this in June with my 1 GM10. Dead simple to rebuild the top end- three wrenches and a screwdriver were all it took to tear the top end down, my old air cooled vw valve compressor did the trick to get the valves out of the head, and then a quick clean up and a new valves, injector, head gasket AND exhaust gasket from this:
Ships Store 1GM10 Common Rebuild List-Sailboat Engine Parts and Boat Parts-Torresen Marine
the rebuild kit I ordered. I didn't need all of it , but it was cheaper and easier than ordering parts piecemeal.

Total time, from turning the first wrench to unbolt the head to bleeding the fuel lines: 5 hours. That includes an hour of bloody bleeding!
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Old 13-12-2010, 07:23   #10
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Get TWO elbows, one as a spare... Your's is a few years past nedding replacing.. Number one cause of carbon build up in a 1GM is NOT letting it get up to temperature. It needs to be run HARD every once in a awhile...Leaving the slip, motoring a few humdred yards and shutting it off will do it every time....

I replace my head after a leaking elbow water jacket allowed cooling water to eat through the exhaust port, as I could see the pushrod from outside...

Yanmar lists the elbow as a maintenance/spare part with good reason..
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