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Old 23-07-2013, 09:51   #76
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Re: I was bored so pulled the head on my yanmar

As I've mentioned before, it seems to be a not uncommon thing in the 3GM30 for some reason.... and most I've heard of (including mine ) were early/mid 90's engines. Go figgur... Mine had no broken rings and no scoring... just a broken piston land allowing the ring to release pressure when It should be holding....
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Old 23-07-2013, 10:12   #77
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Re: I was bored so pulled the head on my yanmar

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Originally Posted by sailorchic34 View Post

Still have to find someone with a dial bore gauge.
if you've got a micrometer large enough all you need is a set of these to measure the bore.

6 Piece Telescoping Gauge Set
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Old 23-07-2013, 11:12   #78
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Re: I was bored so pulled the head on my yanmar

I'm not a diesel guy, so not sure if diesels have higher tolerances, but the bore doesn't look too bad. Given you need a new piston already, you can go oversize so no problem.

Any quotes on parts and prices?

I immediately start thinking electric propulsion..
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Old 23-07-2013, 13:45   #79
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Re: I was bored so pulled the head on my yanmar

My mechanic buddy came over looked at the cylinders. He said it has to be bored. While the photo's don't look all that bad, there is a lip at the top of the oil ring grooves.

So, Honing is off the table and I am taking the engine further apart. Joy joy...
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Old 23-07-2013, 16:25   #80
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Re: I was bored so pulled the head on my yanmar

The design and machining of the piston looks fine, but the failed land brings the material quality in question. If oversize replacements can be obtained from a manufacturer of good repute that choice might be worth considering.
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Old 23-07-2013, 16:27   #81
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Re: I was bored so pulled the head on my yanmar

I don't see why a ridge reamer would be a problem for anyone. You can rent one from an auto store. I'm talking about the type that is used with a 1/2" drive ratchet. Not a power reamer. Just go slow and sneak up on it.
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Old 23-07-2013, 17:33   #82
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Re: I was bored so pulled the head on my yanmar

Ah, its not the standard ridge above the top ring. Its at the oil ring height and only spans 30 degrees or so, where the broken land is. Above that the cylinder is more or less a stock bore.

Have the engine mostly apart. but need a special tool to remove the nut holding the gear on the crankshaft. A 36mm socket with a 6" depth. Had another boater guy helping, so the engine disassemble was going quick.

Also have a line to a machine shop who said they could sleeve the bad cylinder back to stock size and hone the other two for $350.
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Old 23-07-2013, 17:59   #83
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Re: I was bored so pulled the head on my yanmar

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Originally Posted by sailorchic34 View Post

Also have a line to a machine shop who said they could sleeve the bad cylinder back to stock size and hone the other two for $350.
The thinking being, it's cheaper to sleeve the one cyl. with 1 new std.piston and just new rings on the others rather than rebore all of them to oversize with all new pistons. Maybe buying all new pistons would be worth it even though you would be just getting a hone job on the other cylinders. Nothing like new pistons and a valve job. You are doing the rod bearings too?
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Old 23-07-2013, 18:10   #84
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Re: I was bored so pulled the head on my yanmar

Does Yanmar offer oversize pistons? This whole thing is a shame... 1100hours... geez. I've not been a Yanmar fan for quite a while but this takes the cake...
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Old 23-07-2013, 18:26   #85
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Re: I was bored so pulled the head on my yanmar

Yes I would do the rod bearings too. Pooped and messy for the 6 day in a row. Yuck. Have not heard back from the yanmar dealer if the .10 over is available. One sleeve might be cheaper then over size.
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Old 23-07-2013, 18:29   #86
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Re: I was bored so pulled the head on my yanmar

You can't just bore the one cyl to oversize and get one new piston and rings?
Do they not make oversize or not sell the parts separately?
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Old 23-07-2013, 18:31   #87
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Re: I was bored so pulled the head on my yanmar

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Originally Posted by Cheechako View Post
Does Yanmar offer oversize pistons? This whole thing is a shame... 1100hours... geez. I've not been a Yanmar fan for quite a while but this takes the cake...
over sized pistons are available in +0.25 and +0.50mm

here is a good list of parts to rebuild a 3GN30F


http://www.advancemarine.com.au/parts/qrg/3gm30f.pdf



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Old 23-07-2013, 19:10   #88
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Re: I was bored so pulled the head on my yanmar

Looking at your image of the pulled piston, there looks like no indication of blow by (No scorch marks, not even blemished). That means the piston was damaged pulling it out.
So check your bore make sure its parallel. Be careful with your assembly. Good luck.

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Old 23-07-2013, 19:15   #89
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Re: I was bored so pulled the head on my yanmar

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Originally Posted by Oceanride007 View Post
Looking at your image of the pulled piston, there looks like no indication of blow by (No scorch marks, not even blemished). That means the piston was damaged pulling it out.
So check your bore make sure its parallel. Be careful with your assembly. Good luck.

Oceanrider
I have never seen anybody damage a piston like that by removal..........nor have I seen the cylinder scored during removal.
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Old 23-07-2013, 19:19   #90
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Re: I was bored so pulled the head on my yanmar

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Yes I would do the rod bearings too. Pooped and messy for the 6 day in a row. Yuck. Have not heard back from the yanmar dealer if the .10 over is available. One sleeve might be cheaper then over size.
.1? wow, that's alot. I'm thinkin .030.... is that damage that deep?
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