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Old 01-05-2013, 05:00   #1
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Yanmar 3GM engine

Hi everybody I am new to this forum, so I hope I am doing the accepted things.
I have a Yanmar 3GM in my Prout Quest and it is smoking , blue smoke at higher revs. I guess it is well worn with 1426 hours on the clock. The engine is usable but I am concerned. So I am wondering if I should try to buy a used 3GM or 3gm30 so that I can rebuild it and install it if needs be.

I am told that if the engine needs extensive rebuilding it will not be cost effective. I would welcome any comments and if you know of an engine for sale perhaps you could let me know.
All the best Graham
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Old 01-05-2013, 05:33   #2
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Re: Yanmar 3GM engine

1426 hours is not very high for engine hours, in fact I think that's pretty low. What exactly have you been told re repairs? How is the compression? Have you had the engine checked by a mechanic or is it just what others have told you. I know this is more questions rather than an answer but before you proceed you need more facts. And finally, what guarantee do you have that another used engine will be in better shape than your present engine.
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Old 01-05-2013, 05:55   #3
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Re: Yanmar 3GM engine

Blue smoke means that your engine is burning oil. Probability of piston rings gone bad (worn out) is pretty high.

Cost wise: I did a complete overhaul of my 3GM a couple winter ago for around a thousand bucks. This included 3 new rings set, 3 new pistons, bore cylinders oversized, new valves set and reseating, 3 new injectors plus other items like gaskets, seals, bearings, etc...

My mechanic (me) is cheap. I don't know how much but I would expect a paid one would cost you a fair chunk of change to do the job. On the other hand I did a complete overhaul, replacing lots of hardware. Just honing the cylinder walls and replacing rings would be cheaper and easier. Maybe $150 worth of rings, $60 to hone the cylinders, new gaskets + Labours!!!!!

However, if I were you, I would go the overhaul way. Buying an old engine to replace an old engine would only leave you with two old engines. An overhauled one will last you for years.

My two cents...
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Old 01-05-2013, 05:58   #4
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I have Yanmar 75hp turbo diesel in my yacht. It's done 3000 hours and in good order. It also blows blue smoke. In yachts this is common thing as bores get glazed due engine idling and used on low revs long periods. Diesel engines are designed to work hard. This glazing of bores in cylinders is not a concern and I won't do anything about it. Have to watch the oil levels though.

Cheers
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Old 01-05-2013, 06:12   #5
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Re: Yanmar 3GM engine

Greetings and welcome aboard the CF, Graham.
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Old 01-05-2013, 06:19   #6
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Re: Yanmar 3GM engine

If the oil burning is due to cylinder wall glazing which I suspect it is, since these engines can go many thousands of hours then there may be an easy fix.

Run the engine at 3,400 rpm for a couple of hours. This will heat the engine fully and probably burn off some or all of the glaze.

David
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Old 01-05-2013, 06:24   #7
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Re: Yanmar 3GM engine

I pulled my 3HM35F (almost the same engine as yours) out at about 6000 hr when it started burning oil, drove it to Union, NJ where Mac Boring rebuilt it ($4700+), drove it back three weeks later, and reinstalled it. That was a complete rebuild - long list. They do it every day, so the experience is there. I was thrilled to see two others just like mine on the bench at the same time.
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Old 01-05-2013, 06:25   #8
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Re: Yanmar 3GM engine

Check your prop.
Is it fouled, chipped or bent?
These engines burn excess fuel if overloaded
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Old 01-05-2013, 06:27   #9
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Re: Yanmar 3GM engine

My 3 cylinder Yanmar starting smoking and eventualy quit and wouldn't start, smoke wasn't blue though, more gray, and turned out to be the mixing elbow was plugged solid. Can't move anything out so it wouldn't let anything in.
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Old 01-05-2013, 06:31   #10
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Re: Yanmar 3GM engine

I'm not sure where you are but I've always found the Yanmar dealer in Cocoa, Florida to be fair with advice and parts pricing. They rebuild engines there as well and have a fellow that does only that all day every day. Good people.
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Old 01-05-2013, 07:32   #11
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Re: Yanmar 3GM engine

Same experience as dlockhart. Only 1100 hours on my 3GM30F and the mixing elbow was over 50% blocked. This should be considerd a maintenance issue that you need to check every few years. If the mixing elbow is blocked at the hose end, it is probably also blocked at the threaded side.
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Old 02-05-2013, 10:29   #12
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Re: Yanmar 3GM engine

Thank you for such positive comments especially about the hours not being very high.
I have had the boat for about 5 years and the engine has always been very good -starting on the button even in winter when very cold.
The engine was like that when i took the boat out of the water last autumn.
Just before it was lifted back into the water I started the engine briefly. It started as usual with no problem but I did not run it for long because there was no water cooling.
When it was back in the water I tried to start the engine again about 1 and half hours after starting it on land. The engine coughed and spluttered and was reluctant to start. It did eventually fire but on one cylinder only. After perhaps 2 minutes the second cylinder cut in and then after a further 2 minutes the third cylinder cut in. It ran 'rough' for several minutes then decided to work properly and revved up to 2500 RPM .
The engine produced black smoke for a bit but this expected as there was plenty of unburnt fuel in the system.
Then it started to produce clouds of blue smoke when revved over 1700 RPM.
It looked to me as oil engine oil smoke ( petrol car engine experience).
I moored the boat and had to leave it for a few days.
Today I went to the boat and started the engine. I am pleased to say it seemed to run perfectly OK and just as it has been doing for the last 5 to 10 years.
Someone suggested that the injectors must have been a bit ' cruddy' and have now cleared themselves.
I do not know anything else.
I have had comments from club members mostly along the lines that on the road I would have been arrested for pollution!
I have not had a marine/diesel mechanic take a look and at present it would be wasted because the engine seems to be fine.
But it is a mystery and I would like to know what the problem was or is. Although the boat is a catamaran it only has one engine and I would like to be confident that it is reliable.
Once again many thanks for your comments and your interest. If you have further suggestions please let me know.
What I was and still am thinking is that if I got a second engine I could strip it down and thoroughly check it etc. Then if I needed I could put it in my boat. I could then sort out my old engine and either keep it or sell it on.
Thank you
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Old 09-12-2013, 09:56   #13
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Re: Yanmar 3GM engine

News Flash...

Pierre, please check your PM's. I'm hoping to get some info on your trip to the bay of fundy. I wrote last year after you said I was the previous owner of your boat.

Back to your regular programming...
Paul.
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Old 09-12-2013, 13:48   #14
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Re: Yanmar 3GM engine

Now that it seems to be running ok, watch the oil level. If it is burning oil and any more than a quart between 100 hour oil changes is a lot, then try running for several hours at full load as I suggested earlier in this thread. That may improve oil consumption. With easy starting the engine is not worn out.

David
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