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Old 11-11-2013, 15:43   #1
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Does the Yanmar 2GM20 have dry sleeves?

I have been reading the 2GM has a removable press-in sleeve.

Does the 2GM20 have the same setup? If not, can oversize pistons be obtained for the 2GM20 engines?

Just trying to plan ahead for a rebuild on my 2GM20.

Thanks everyone!
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Old 11-11-2013, 16:35   #2
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Re: Does the Yanmar 2GM20 have dry sleeves?

The gm series engines are not sleeved at all. At least not the later year models I did have my 3gm bored and sleeved on the one hole that went bad. Machining the one hole and honing the other two was $270 in California at a good auto machine shop. Oversize pistons are available. First oversize is about $150 per piston/ring set. second oversize is more. Boring and sleeving the holes is also an option. Stock piston size with rings is about $90.

How many hours on your 2gm20. My 3gm had a stock bore size after 1100 hours. Well except for the bore where #3 piston lands failed. Even the old rings were within stock new size as I compared the old to new when I rebuilt my 3gm30
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Old 11-11-2013, 17:21   #3
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Re: Does the Yanmar 2GM20 have dry sleeves?

When I look at the top of the block it sure looks like there are sleeves. Man...

So the motor I bought is a basket case from a boat that flooded. The top end flooded with salt water so there is surface rust in the cylinders and the head. The transmission, bottom end and everywhere else are spotless though.

It's in pieces because the pistons were frozen. The cylinders look okay but the old pistons are done as are the rings.

I got the entire motor for $300 bucks cash so I figure rebuilding it is worth the risk.

It reportedly had under 100 hours when it flooded.
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Old 11-11-2013, 17:47   #4
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Re: Does the Yanmar 2GM20 have dry sleeves?

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When I look at the top of the block it sure looks like there are sleeves. Man...

It reportedly had under 100 hours when it flooded.
That's what I thought too, that it was sleeved. But the Yanmar GM shop manual said its not sleeved. If it only had 100 hours, I would just hone the walls lightly and put new rings/pistons in.
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Old 11-11-2013, 17:49   #5
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Re: Does the Yanmar 2GM20 have dry sleeves?

So would you say that my best course of action would be to have a shop do a light hone and then give me a measurement of the new bore size so I can order the appropriate pistons?

Want to come visit me in Monterey?? Rumor has it that you own a certain deep socket I need to use :-)
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Old 11-11-2013, 17:58   #6
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Your not going to change the bore with a hone, appreciably anyway not unless you are real determined, but yes of course mic the hole, look for bore taper and see if there is a ridge at the top of the bore where the rings stop, both would indicate wear not consistent with 100 hours. Any decent shop will do this anyway, Oh and if your going to do it yourself, stay away from "dingle berry" hones, they are junk and can cause problems
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Old 11-11-2013, 18:18   #7
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Re: Does the Yanmar 2GM20 have dry sleeves?

What is a ball park price for a rebuild which would include valve job, honed, cam bearings, done at a machine shop. Then put back together by the owner. Many mango seasons ago I use to be a mechanic at a shop but have no experience with diesels.
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Old 11-11-2013, 18:20   #8
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Re: Does the Yanmar 2GM20 have dry sleeves?

It's my understanding the GM 1980-83 engine are sleeved with smaller pistons. The GM10, 20, 30 etc are not sleeved.
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Old 11-11-2013, 18:28   #9
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What is a ball park price for a rebuild which would include valve job, honed, cam bearings, done at a machine shop. Then put back together by the owner. Many mango seasons ago I use to be a mechanic at a shop but have no experience with diesels.
Add turn the crank if necessary, rebuild the injectors and pump, and I'd plan on boring the cylinders, I'm not a fan of a "ring job", and replace the accessories, at least the water pump and thermostat.
Difference between Diesels and gas motors as far as being a mechanic is not much at all, just learn how to time the injection pump, sometimes it's so simple you can't screw it up, really I'd rather do Diesel work.
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Old 11-11-2013, 18:37   #10
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Re: Does the Yanmar 2GM20 have dry sleeves?

Thanks the admiral and I are contemplating looking at catamarans with 30 HP engines that would be around 10 years old and trying to get a feel for rebuilding costs. Hopefully we wont have to worry about it, but just curious. Hadn't thought about the injectors (good thinking) but absolutely on the boring, crank and accessories thanks.
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Old 11-11-2013, 18:43   #11
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I'd think the machine work would only be a couple of hundred dollars, parts? I can't even guess. Now if you want to overhaul an IO-540, I can give you a decent quote there.
I've heard of people spending 20K replacing a 4 cyl. Yanmar, but can't for the life of me see how it could cost that much. by replacing I assume a new 0 time engine, but still 20 K?
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Old 11-11-2013, 19:11   #12
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Re: Does the Yanmar 2GM20 have dry sleeves?

So Toad marine supply has the 2GM20F rebuild kit 2GM20F Rebuild List - Pre 1997 Sailboat Supplies, Engine Parts and Boat Parts
for about $1200 which includes new pistons, rings, injectors, and what looks like most bearings and gaskets. Might just get that?
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Old 11-11-2013, 19:42   #13
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Re: Does the Yanmar 2GM20 have dry sleeves?

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So Toad marine supply has the 2GM20F rebuild kit 2GM20F Rebuild List - Pre 1997 Sailboat Supplies, Engine Parts and Boat Parts
for about $1200 which includes new pistons, rings, injectors, and what looks like most bearings and gaskets. Might just get that?
It cost me about $700 for my parts, without injectors and not all gaskets, just the complex ones. Going to .01 over will add $150 ish for a 2 gm and $200 ish for 0.02" over. The small gaskets can be made from gasket paper. Bearings are cheap as is most gaskets.

My 3GM30 had 1100 hours on it and the everything measured within stock "New" tolerance, bore, rings, ring groove, etc., Except for the broken piston and buggered up cylinder wall on #3. So I elected to have #1 and #2 honed lightly and #3 bored and sleeved to keep the stock sizes. This allows for at least 2 additional rebuilds. Not that I'm planning on another rebuild.
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Old 11-11-2013, 19:52   #14
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Re: Does the Yanmar 2GM20 have dry sleeves?

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Originally Posted by Dexterbase View Post
So Toad marine supply has the 2GM20F rebuild kit 2GM20F Rebuild List - Pre 1997 Sailboat Supplies, Engine Parts and Boat Parts
for about $1200 which includes new pistons, rings, injectors, and what looks like most bearings and gaskets. Might just get that?
AH, but Yanmar generally prohibits dealers from selling parts outside their area. Lucky California is all one area. Alas no one in the state offers internet sales. At least none that I could find. You have to go to the local dealer. The distributor for the state is Boatswain's Locker, Inc 931 W. 18th Street
92627 Costa Mesa (949) 642-6800.

Boatswain does not stock that much, so most of the parts have to be shipped to them from Georgia first. A delightful experience.... Not.
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Old 11-11-2013, 19:56   #15
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Re: Does the Yanmar 2GM20 have dry sleeves?

The Toad website store looks like it'll let me check out. I added all the parts to my cart and it's asking for CC information.

I wonder if I'll just get a phone call tomorrow telling me they can't ship to me?
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