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Old 21-07-2013, 10:28   #46
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If you can keep Outboards running your a better mechanic then me or you have to much time on your hands.
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Old 21-07-2013, 10:29   #47
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Re: I was bored so pulled the head on my yanmar

Well from research I found that marine engine cylinders are numbered from rear / stern of the engine forward. So keeping with that, #3 is actually the one closest to the fan belts. Its the highest, as there is a slight 5 degree slope to the engine.

#3 is also the only one with vertical scuffing / grooves. An any event, I
am doing woodwork today getting wood ready to sit the engine on and also rig rope and chain for tomorrows engine pull.
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Old 21-07-2013, 10:36   #48
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Re: I was bored so pulled the head on my yanmar

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Only 1100 hrs.

That does not speak well.
I had two 1992 3GM30's. One failed under 500 hours... replaced under warranty. The other had the same problem as Sailorchic's... broken piston at about 2200 hours if I remember correctly. Luckily I didnt score the cylinder wall.
I wonder if you can get an oversize piston and have that cylinder bored a little?
The big question is...with Yanmars apparant problems in these early 90's engines... do you replace all the pistons/rods? and are the new ones better?
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Old 21-07-2013, 10:46   #49
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Re: I was bored so pulled the head on my yanmar

Below is a photo of the wear in #3 You can see vertical grooves and I can feel a small ridge at the top. On the left of center there are two larger grooves. Main wear is at the top of the stroke. The rest of the cylinder is not so bad with light scoring mainly from 12 to 3 oclock. The photo is looking at 3 oclock. 12 oclock is front of engine.
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Old 21-07-2013, 10:47   #50
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Can't you get a ring that is up a micron.
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Old 21-07-2013, 10:52   #51
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Re: I was bored so pulled the head on my yanmar

Hard to tell from the pics... doesnt look too bad... hopefully not deep!
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Old 21-07-2013, 10:55   #52
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Re: I was bored so pulled the head on my yanmar

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I had two 1992 3GM30's. One failed under 500 hours... replaced under warranty. The other had the same problem as Sailorchic's... broken piston at about 2200 hours if I remember correctly. Luckily I didnt score the cylinder wall.
I wonder if you can get an oversize piston and have that cylinder bored a little?
The big question is...with Yanmars apparant problems in these early 90's engines... do you replace all the pistons/rods? and are the new ones better?
At the moment, I'm thinking of just doing a repair/replace on the one cylinder. The other two are fine and oil pressure was never below 60 psig when running. Really I don't quite trust that the new parts are any better then the old parts.

My plan of attack is to run a ball "flex" hone through #3 and see if I can get it close enough and throw a new set of rings in it. If I had the money I would re-ring all three. But well just getting one set of rings and a few gaskets will pretty much break my bank. If it must be machined, I'll figure something out.
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Old 21-07-2013, 10:59   #53
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Re: I was bored so pulled the head on my yanmar

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Hard to tell from the pics... doesnt look too bad... hopefully not deep!
Its not that bad, but I can feel a lip at the top of stroke, maybe .001 or .002, just where the grooves are. Seeing if I can brorrow a dial bore gauge to measure the inside. My thought is since there is no ridge at the top of the cylinder, that in theory anyway, I can just hone it and throw a new set of rings on it. That's the plan at the moment.
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Old 21-07-2013, 11:31   #54
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Re: I was bored so pulled the head on my yanmar

Yeah... might be just fine.... if it's a broken piston, send us a pic!
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Old 21-07-2013, 11:56   #55
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Re: I was bored so pulled the head on my yanmar

Hey, before you remove the engine, measure everything as a startpoint for re-alignment in installation. I use 1/2" aluminum solid bar, and make gauges.

Is it not possible to invert the block in situ? pull the sump and crank right there?

Did that on a V8 Gas engine, I could just lift the block and flip it by hand with everything off it. pictures here...
spring and summer 2005
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Old 21-07-2013, 12:00   #56
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What's the cost break down of doing all the rings. Compared to gaskets and one set? What was the cause of failure?
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Old 21-07-2013, 12:30   #57
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Re: I was bored so pulled the head on my yanmar

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Hey, before you remove the engine, measure everything as a startpoint for re-alignment in installation. I use 1/2" aluminum solid bar, and make gauges.

Is it not possible to invert the block in situ? pull the sump and crank right there?

Did that on a V8 Gas engine, I could just lift the block and flip it by hand with everything off it. pictures here...
spring and summer 2005
I'm cheating. I'm lifting the engine, mounts and all. The mounts bolt to the frame so when the mounts line up with the holes it close. I'll still do an alinement of the prop shaft once its back in. I have to do it that way so I can slide the engine back, so the v-drive is removed from the prop shaft. See photo below.

I'm guessing the engine went in on the hard with the prop shaft going in after the engine was in place The prop shaft runs through the lower unit of the vdrive. I have to slide the engine back 8-10 inches to clear the lower unit from around the prop shaft. Then the engine can be lifted up and out.

The wood floor brace will be cut and removed later today. That's the last part to do before removing the engine.

There just is no space to move even get to the oil pan bolts let alone dropping the pan, while its inside. I'm making a frame for the engine to sit on outside that will let me drop the pan and pull the pistons. I will be posting photo's once everything is apart and I start measuring.
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Old 21-07-2013, 12:39   #58
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Cheating might not be good. Take a breath and look at where you are. Think you are way competent but sometimes we get to close and need to step back. Reevaluate cause and some cost options. Would really suck to get this far and not get it back right. Maybe it takes a little longer maybe your right and you can cut a corner but stopping and looking big picture is cheap.
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Old 21-07-2013, 12:57   #59
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Re: I was bored so pulled the head on my yanmar

Oh I admit that getting the bolt holes back exactly over / under the mounting holes will be more then a little fun. But there really is only one way this engine is coming out while the boat floats. The prop shaft is my guide when it goes back in as it only has about a 1/4" wiggle room anyway, side to side. front to back the prop shaft only moves 2" or so due to aperture prop.

Oh one mount is staying as it can't slide forward. So the left rear transmission mount will be unbolted at the transmission.

The fun part will be getting the prop shaft coupling back on. May have to heat it up to slide it back on as the back end will be resting against the rudder. (barn door rudder) I actually have to put that back on with the engine moved a few inches back so I can tap it even with the prop shaft. The whole boat is like that, all 1/2 inch clearance
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Old 22-07-2013, 11:19   #60
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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
At the moment, I'm thinking of just doing a repair/replace on the one cylinder. The other two are fine and oil pressure was never below 60 psig when running. Really I don't quite trust that the new parts are any better then the old parts.

My plan of attack is to run a ball "flex" hone through #3 and see if I can get it close enough and throw a new set of rings in it. If I had the money I would re-ring all three. But well just getting one set of rings and a few gaskets will pretty much break my bank. If it must be machined, I'll figure something out.
I think you might be OK with this plan...

The pics don't look too bad... The vertical scores I think should "mostly" come out with the ball hone... The ridge at the top doesn't look too terrible...

BUT...

You could possibly break the piston land (piston material between grooves) if the ridge catches a ring ... That would be bad on a budget! Using a ridge reamer probably isn't the best idea for a first timer here... I think pushing the piston down and a couple of passes with the ball hone before you pull the piston would break the edge of the ridge down enough... Don't go crazy here... You are going to do your ball hone magic after the piston is out...

If it were me, I would hone all 3, three ring sets, and lap the valves (your labor only)... But you are bottom budgeting... You are however going to rethink this after honing #3... Excited about how pretty your new cross hatching looks and glance disapprovingly at the other two!

Keep us up to date with pics in progress... We want to see pics of the piston, bore before honing, etc... With all of the other great help you are getting we will get this baby purring again!
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