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Old 22-07-2013, 11:35   #61
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Re: I was bored so pulled the head on my yanmar

The ridge at the top is only at one place and not all around. Plus it is pretty shallow. I'm hoping that the rings compress enough around the non-worn spots to make it out. Got the block and tackle's connected. Now just waiting for a few live bodies to show up for the engine removal.
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Old 22-07-2013, 11:37   #62
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Re: I was bored so pulled the head on my yanmar

it'll be interesting to see if the land is what's already broken. Compare the new piston with the old. If different, then I would go for all 3.... easy for me to say!
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Old 22-07-2013, 15:49   #63
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Re: I was bored so pulled the head on my yanmar

Oh lordy, that was too much fun. The engine is out and on the deck. There is another photo of #3 and one of #1 which some horizontal scoring. Lovely. Its looking like all three cylinders need honing and #3 might need to be bored out. Will know more tomorrow.

Just a little pooped at the moment.
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Old 22-07-2013, 17:42   #64
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Re: I was bored so pulled the head on my yanmar

Hi again Sailorchic34 (Is that your age or the boat length?)

I think you are on the right track in just concentrating on the cylinder which has the problem and leaving the others alone.

It is hard to make out the full nature of the markings in the cylinder wall but to my eyes they appear as scuffs rather than scores and if so there is a good chance honing it will be sufficient.

The 3GM30 is a marinized industrial diesel and probably tens of thousands of them were produced. Rather than get involved in extensive repairs I would go look for a complete used engine to replace your existing one. I found Yanmar parts horrendously expensive and used industrial engines tend to be readily available and fairly cheap.
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Old 22-07-2013, 17:53   #65
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Re: I was bored so pulled the head on my yanmar

Oh joy.... To answer which ring was broken.... All of them and two piston lands too. Joy Joy. See photo. Top ring was broken in one place. Second ring was shattered into oh 40+ pieces. Oil ring was in 4 pieces. The piston just slid out too

I'm going to pull the other two pistons tomorrow and see what they look like. Thinking I'm going to write Yanmar a nasty gram. This should have never happened with 1130 hours on the engine.
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Old 22-07-2013, 17:58   #66
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Re: I was bored so pulled the head on my yanmar

S c ..a ball hone will not make your bore round or straight perhaps you can find a rich it hone
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Old 22-07-2013, 19:03   #67
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Re: I was bored so pulled the head on my yanmar

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Hi again Sailorchic34 (Is that your age or the boat length?)

I think you are on the right track in just concentrating on the cylinder which has the problem and leaving the others alone.

It is hard to make out the full nature of the markings in the cylinder wall but to my eyes they appear as scuffs rather than scores and if so there is a good chance honing it will be sufficient.

The 3GM30 is a marinized industrial diesel and probably tens of thousands of them were produced. Rather than get involved in extensive repairs I would go look for a complete used engine to replace your existing one. I found Yanmar parts horrendously expensive and used industrial engines tend to be readily available and fairly cheap.
If the bores are gone I could see that, but why would she scrap an engine with only 1100 hours on it to buy an unknown used one with probably 3-10 times the hours?
Some Yanmar parts are abusively expensive, however when mine was fixed in the USVI everything including the labor to R & R was about $2000. We replaced the rods and pistons as an assembly and as I remember it, they werent too darn bad...
It'll be interesting to see how much the pistons are now.... The land on mine was simply broken and floating free... causing no damage, hope you can salvage that Sailor chic! I'm rooting for ya!
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Old 22-07-2013, 20:02   #68
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Re: I was bored so pulled the head on my yanmar

The 34 in SC34 is the boat length. My mental age is younger then 34, but my physical age is getting up there to the point where I've had to start dividing by 2 seven years ago.

With only 1130 hours, most of the engine is just getting broken in. Other then the wear in #3, there isn't a ridge in the cylinder walls. As the wear limit for standard size rings is .004 over I'm hoping I can just hone my troubles away.

Still have to find someone with a dial bore gauge.
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Old 22-07-2013, 20:27   #69
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Re: I was bored so pulled the head on my yanmar

I dial bore gauge will be much harder to find then and inside micrometer which is very accurate and tells you all you need to know
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Old 22-07-2013, 20:35   #70
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Re: I was bored so pulled the head on my yanmar

I've a micrometer, but the inside measuring is not deep enough to even measure the top of the ring bore. It can measure the top of the bore, but I need to measure where the rings wear.

I just have to hunt down my favorite mechanic and see if I can borrow one. Actually I need to tell his wife, as he tends to forget.
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Old 22-07-2013, 23:34   #71
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Re: I was bored so pulled the head on my yanmar

Good luck with Yanmar.
I had a leaking freshwater pump at 250 hours, and they told me I was on my own.
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Old 23-07-2013, 02:10   #72
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Re: I was bored so pulled the head on my yanmar

The bore doesn't look to bad and whilst the piston is a mess re rings and lands other than that the piston looks pretty good ie not scored down the side from broken ring particles.

I seem to recall there was a thing you could do with putting a piston ring into the bore and measuring the gap between the ends with feeler gauges which would give you a pretty good indication of cylinder wear.

Whilst my 3GM30 proved to be an excellent little motor in it's later life it did not start off well. From new the engine kept blowing head gaskets until the block needed skimming. When I asked the local agent did I need to also skim the pistons to retain piston overhead clearance he referred the inquiry to Yanmar in Japan and they sent me a new block. The motor was out of warranty and there was no explanation as to why they felt obliged to give me a replacement block. I had to rebuild the engine myself but I purchased the shop manual and found a few other things wrong, for example non rotating cam followers, which would have caused problems at a later date.

If the local agents are unsympathetic I would be inclined to go direct to Yanmar in Japan with the story, and also refer to this site, they may just decide to come to the party particularly if they see the sort of bad publicity they are getting. Aint this internet thing wonderful.
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Old 23-07-2013, 07:00   #73
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Re: I was bored so pulled the head on my yanmar

Hi, Re broken rings, Assembly of rings is critical, I hope you have a devise that prevents them from being strained on assembly. Its not likely a fault at original assembly as you have land failure, I reckon that is a cause, not effect. A ring once it breaks would go down to the bottom of the ring groove, it cant get in the gap between bore and piston, the scoring is caused by the spring tension of the ring end pushing out. I wouldn't much worry about the score in bore as indicated, its really only a worry if the gas pressure on the circumference of the ring is greater than the pressure at the back of the ring collapsing the ring, but your score is tiny. More interested in roundness parallel bore and cross hatching to aid lubrication.

Land failure in this manner, never seen it myself, have to conclude it was damaged before it went into your engine, your unlucky. Rings should be free in groove, butt clearance checked.

Its not likely but I suppose it is possible that the bore diameter was tapered just a little that allowed the rings to over fatigue and eventually break, but that doesn't explain the land failure. Hitting the ring groove at top not likely either. But it does have to be removed now.

In a nut shell, check your bore is parallel and round, rings like to rotate. Use a devise to ensure the original spring tension in the rings is not strained. Remove the lip at top of bore, the glossy surface of the bore must be dulled. All detritus esp from hone balls or stones must be removed. Ensure your ring gap is correct. Your head sounds like its OK, I'd risk it.

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Old 23-07-2013, 08:13   #74
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Re: I was bored so pulled the head on my yanmar

My one lucky thing is other then where the wear is at 3 oclock at #3 there is no ridge at the top of the cylinder. If there is a ridge and mind you I can not feel any imperfection at all in any cylinder, then the wear is most likely under 0.0005 inch. Honing with a flex hone should take care of that just fine.

The engine at 1100 hours should really just be nicely broken in and in everything else shows no measurable wear

Actually using a ring from another cylinder and checking end gap would be an excellent idea. Yes I need a ring expander tool too.
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Old 23-07-2013, 09:24   #75
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Re: I was bored so pulled the head on my yanmar

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Oh joy.... To answer which ring was broken.... All of them and two piston lands too. Joy Joy. See photo. Top ring was broken in one place. Second ring was shattered into oh 40+ pieces. Oil ring was in 4 pieces. The piston just slid out too

I'm going to pull the other two pistons tomorrow and see what they look like. Thinking I'm going to write Yanmar a nasty gram. This should have never happened with 1130 hours on the engine.
Wowsa....

I have never seen such damage done by somebody pulling a piston before!


First of all... An I think we can all agree here.... What a crap piston/material design to have this much catastrophic damage... Lands failed first? Rings? We can chicken and egg this thing to death, but I am in the Land Boat...

My honest guess is that overzealous use of starting fluid was the demise of #3 cylinder... Explosive compression the piston wasn't designed for, and lack of lubrication in the hole...

I still truly believe if you go the "put this one together route" by finding reasonable piston prices, that there will be no problem with the bores... Out of roundness wear, or honing out the scores...

Let us know about your bore measuring device search... And the results of the inspection of other two holes...

PS: Chin up... It could have been worse....
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