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Old 03-08-2021, 23:33   #1
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Yanmar rebuild or new ?1gm10

So i have a project boat , a lovely old catboat with oem 20 yr old yanmar 1gm10 cast iron block.. Engine loooks like it has blown a head gasket, it was known to have run hot without its raw water cooling for 5 minutes or so during a disastrous effort at winterizing. Before that disaster the engine did run but according to its previous owner (my seller) was throwing clouds of black sooty smoke and was the scourge of its marina (which is why he sold the boat at a very lowball price.) I suspect the following: 20 years in saltwater, no competent maintenance, diesel mechanics not around, seller never bothered to do simple maintenance let alone flush salt out of the water passages in the block at haulout. He said injector and exhaust elbow were supposedly worked on but didnt cure black smoke.

Looking for advice on my options: if the1gm cylinder wallhas developed the famous pinhole corrosion, known to be a possible cause of excessive black smoke ,, is there any fix short of putting in a whole new yanmar engine ? I have a couple good yan mechanics locally , unlike previous owner, but would like to hear all thoughts and suggestions before having the boat towed 100 miles to one of them...



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Old 03-08-2021, 23:43   #2
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Re: Yanmar rebuild or new ?1gm10

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Originally Posted by kaisardog View Post
So i have a project boat , a lovely old catboat with oem 20 yr old yanmar 1gm10 cast iron block.. Engine loooks like it has blown a head gasket, it was known to have run hot without its raw water cooling for 5 minutes or so during a disastrous effort at winterizing. Before that disaster the engine did run but according to its previous owner (my seller) was throwing clouds of black sooty smoke and was the scourge of its marina (which is why he sold the boat at a very lowball price.) I suspect the following: 20 years in saltwater, no competent maintenance, diesel mechanics not around, seller never bothered to do simple maintenance let alone flush salt out of the water passages in the block at haulout. He said injector and exhaust elbow were supposedly worked on but didnt cure black smoke.

Looking for advice on my options: if the1gm cylinder wallhas developed the famous pinhole corrosion, known to be a possible cause of excessive black smoke ,, is there any fix short of putting in a whole new yanmar engine ? I have a couple good yan mechanics locally , unlike previous owner, but would like to hear all thoughts and suggestions before having the boat towed 100 miles to one of them...



?
https://www.youboat.com/uk/d/boat-en...-package/16294
what you thinking ,or find only engine.
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Old 04-08-2021, 03:55   #3
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Re: Yanmar rebuild or new ?1gm10

Don't know where on the planet you are but if you are in Aus. or NZ I'd say probably not worth rebuilding as parts prices are too high & if you have to pay a mechanic as well..... Even in the USA it wouldnt be cheap if it needs a comprehensive rebuild.

However it also depends on what is wrong with it which you cannot tell without testing &/or mechanical experience or stripping it down.
A new engine is only worth it if you intend to keep the boat a long time otherwise it's better to get a good used engine.
Sadly the 1gm10 does not have replaceable cylinder liner/sleeve so you have to rebore & put oversize piston & rings in. They are pretty marginal in terms of power output. I would prefer something like a 2QM15 or even a ysm12. ( We have a ysm8)
However changing engines can be a lot of work when you need new prop/shaft/mounts etc
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Old 04-08-2021, 07:52   #4
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Re: Yanmar rebuild or new ?1gm10

Here's a $2,700 Yanmar 1gm10 on ebay:

https://www.ebay.com/itm/33405594328...hoCE9YQAvD_BwE

From the sound of it, a complete overhaul is the minimum and replacement is likely to be more economical. That black smoke is not the fault of the exhaust elbow but may be a worn out injector - too much fuel is going to the cylinder.

If there is any good news in this situation it may be that pulling the engine and replacing it with exactly the same model is something plenty of forum members have done without being diesel mechanics. Just avoid like the plague (trusting that you are not a Florida Republican, they seem to like plagues) replacing it with a different make/model. That's a trap - all the hoses, through hulls, cables, mounts, and wires will be in the wrong places and it won't fit.

It is possible, not likely but possible, that the problems with this engine are not useful life ending. It could be that you simply need new injectors. Consider pulling them and testing compression. You have nothing to lose from a bit of disassembly and examinattion.
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Old 04-08-2021, 08:06   #5
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Re: Yanmar rebuild or new ?1gm10

It may be worth removing the engine and disassemble to find out it's condition, especially the head and block. You are going to take it out to replace or rebuild anyway. It's one cylinder so easy peasy to rebuild if those are good. Head rebuilders can check the head for cracks. Have a rebuilder look at the bare block.
I imagine you can lift that engine out once the peripherals are off it...? 2 guys lifted the 3GM30 out of my catamaran with a line to stabilize the load.
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Old 04-08-2021, 08:59   #6
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Re: Yanmar rebuild or new ?1gm10

I had a very similar situation with my YSM8 and went for the rebuild. Good thing. When they took the old one out, they found a crack in the head and corrosion creeping everywhere. Had I gone for the complete disassembly (which I cannot do myself), I would have spent several thousand dollars only to find that it could not be rebuilt. TKeithlu's advice is right on target. If you use a different engine, the labor costs go way up sinceyou have to have new mounts, probably will need a new shaft, etc. If you are looking for a new 1GM10, I would start looking now since they are not always easy to find, at least in the U.S.
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Old 04-08-2021, 09:06   #7
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Re: Yanmar rebuild or new ?1gm10

Another thought is to look for a 2GM. They are very much the same. If you have a wee bit more room available forward of where the 1Gm sits now it may go right in. (6 inches?) A lot smoother running than the 1 cyl too.
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Old 04-08-2021, 12:58   #8
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Re: Yanmar rebuild or new ?1gm10

Ummm, I wouldnt touch that Ebay 1GM10 that is mentioned in previous post. It says compression measures at 250, should be over 400 & minimum 355.
New paint does not make a good engine
Agree with cheechako, much better to get a twin, better still a 3cylinder.
I would go Kubota based if you plump for new, much cheaper parts.
A yanmar ysm8 has much cheaper aftermarket parts available ex Taiwan & they have cylinder sleeves if you want a similar hp option single.
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Old 04-08-2021, 15:35   #9
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Re: Yanmar rebuild or new ?1gm10

I have removed an ancient 1 GM for a rebuild. Take off the Kanzaki gearbox and then remove the heavy flywheel. The engine can then be lifted by one person. The only heavy bit then is the starter motor. But do have a chat with a local Yanmar rebuilder as he may recommend that you dismantle as much of the engine as possible as he will probably need to do that anyway.

Comments about replacing the engine are all warnings. New engine mounts, changed coupling, new exhaust arrangements, wiring, plumbing. New mortgage probably.
I understand that the 1 GM's need to be run at fairly high rpm. See the handbook plus there were recent comments on this in this forum. A larger engine may be exactly the wrong thing to do.

The only worry is that you may suspect you have taken on the responsibility of saving the Japanese economy single handed.

Better the devil you know though.
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Old 05-08-2021, 08:09   #10
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Re: Yanmar rebuild or new ?1gm10

Dismantle and remove the old yanmar yourself. Sell the parts, if you want, or just give it away.

Then install electric drive. Low power (8hp) is a perfect match for electric power. Install as many batteries as you need now, and you can install more later if needed, along with solar and whatever. Its a lot cheaper and simpler than a new diesel.

And instead of being the scourge of the marina, you will me the trendsetter...because we are all going electric sooner or later.
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Old 06-08-2021, 08:17   #11
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Re: Yanmar rebuild or new ?1gm10

thanks for all the thoughts. on the good side this boat is structurally sound , well built, excellent manufacturer support, and is just what we need for our 'retirement' in our 70s/80s as our trailerable (5th and likely last ) boat. i finally got some of the previous engine maintenance/ repair records : it was already 'rebuilt' once in 2014 w install of an oversize piston and cyl liner at which time injector was supposedy ' pulled' and 'worked on' . i've no idea if anyone checked fuel pump for diaphragm crack , or checked fuel pump timing (for presence of proper shims etc.) i presume but don't know for sure from the sketchy records that the 2014 mechanic would have first checked for burnt exhaust valve or coked up intake or exhaust manifolds before undertaking a rebuild. i also don't know if they checked for possible delamination of the old exhaust hose or a clogged exhaust elbow though that would be a logical place to start before the cylinder rebuild... i'm trying to get more info from the previous owner who contracted for the work. at my low purchase price, i'm willing to spend money to get a functional inboard diesel engine and i'll still be under the market value for this year and model with an OEM functional diesel inboard. the new 'drop in' replacement for the 1GM10 is the yan YSM 15 w fresh water cooling but i fear that would require upsizing raw water seacock, a different gearbox, upsizing the propshaft and prop, new b panel, and reworking the exhaust outlet on the transom, etc. which adds a lot more $$ to install cost. so i'll stick w staying in the 1GM10 ballpark but i don't think installing a rebuilt one is a wise choice. 2004 to now is 17 years of salt water in the raw water engine's cooling passages without any freshwater flush , and a fix that didn't work in 2014 . the prior owners had terrible soot and black smoke problems 'for years' at all rpms: start up in neutral , idle to WOT under load . (prop and bottom are clean, prop is oem size and install spec .) if in fact the rebuilt cylinder wall has the dread pinhole leak i see no option to complete 1GM10 engine replacement (aaagh, $$$$$$) .
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Old 06-08-2021, 17:39   #12
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Re: Yanmar rebuild or new ?1gm10

Quote:
Originally Posted by kaisardog View Post
thanks for all the thoughts. on the good side this boat is structurally sound , well built, excellent manufacturer support, and is just what we need for our 'retirement' in our 70s/80s as our trailerable (5th and likely last ) boat. i finally got some of the previous engine maintenance/ repair records : it was already 'rebuilt' once in 2014 w install of an oversize piston and cyl liner at which time injector was supposedy ' pulled' and 'worked on' . i've no idea if anyone checked fuel pump for diaphragm crack , or checked fuel pump timing (for presence of proper shims etc.) i presume but don't know for sure from the sketchy records that the 2014 mechanic would have first checked for burnt exhaust valve or coked up intake or exhaust manifolds before undertaking a rebuild. i also don't know if they checked for possible delamination of the old exhaust hose or a clogged exhaust elbow though that would be a logical place to start before the cylinder rebuild... i'm trying to get more info from the previous owner who contracted for the work. at my low purchase price, i'm willing to spend money to get a functional inboard diesel engine and i'll still be under the market value for this year and model with an OEM functional diesel inboard. the new 'drop in' replacement for the 1GM10 is the yan YSM 15 w fresh water cooling but i fear that would require upsizing raw water seacock, a different gearbox, upsizing the propshaft and prop, new b panel, and reworking the exhaust outlet on the transom, etc. which adds a lot more $$ to install cost. so i'll stick w staying in the 1GM10 ballpark but i don't think installing a rebuilt one is a wise choice. 2004 to now is 17 years of salt water in the raw water engine's cooling passages without any freshwater flush , and a fix that didn't work in 2014 . the prior owners had terrible soot and black smoke problems 'for years' at all rpms: start up in neutral , idle to WOT under load . (prop and bottom are clean, prop is oem size and install spec .) if in fact the rebuilt cylinder wall has the dread pinhole leak i see no option to complete 1GM10 engine replacement (aaagh, $$$$$$) .

Dont forget the ys8 series Yanmars option for replacement, same hp but more sturdy IMO & cheaper replacement aftermarket parts. Not sure if motor mounts same but you dont need bigger shaft or prop or more water.
If the owners keep up with anode replacement the blocks survive fine. Ours is 41 years old & for the first 35 years it never had any fresh water flushing. Its block is hardly corroded.They are noisy shakey beasts but pretty good otherwise once you get an ss exhaust elbow.

I must say I looked at the Ebay 1gm10 video & there is no way it had 250lb compression starting that easy unless the video was edited. It's compression would have to be way higher to start that easy even if hot. Price seemed way high to me though but I'm not in the USA.
It's fraught with danger buying a used diesel if you are not good with engines though. I would have no hesitation in buying a rebuilt ysm8 if I knew & trusted the rebuilder.
But if you dont know how to do it yourself & dont know a trusted rebuilder you are probably better off to buy new.

Hope that helps
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Old 07-08-2021, 13:48   #13
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Re: Yanmar rebuild or new ?1gm10

It should be easy to lift out the engine it is not that heavy. I can pick up a Yanmar 2gm alone so the 1 gm should be doable. A machine shop should be able to do a valve job for about $300 USD. Get some rings and rod bearing and do it yourself, just run a stone cylinder hone in the cylinder and cover the crank when you do it. Clean the ring grooves with one of the old piston rings that you remove and break in half.

Basic functional rebuild that may last longer than you own the boat.
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Old 09-08-2021, 16:27   #14
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Re: Yanmar rebuild or new ?1gm10

i've sourced a rebuilt freshwater 1 gm10 from a very reputable local yan dealer. i'm now comparing cost to pull the old 1 gm10 and install the rebuilt 1 gm10. added costs likely include new engine mounts and exhaust system assuming the morse cables, A panel and gearshift/throttle control are fine. i'm fond of the idea of the new 2 cyl ysm15 but the extra cost of a new ysm and all the changes to engine bed, mounts, s eacocks etc add a lot to the price. curiously, the new 1 gmprice fom the japanese/ indonesian dealers is only $2700 but i fear our us customs will impound it because the new 1 gm 10 s are not EPA approved. yan has a 're engine program ' where they'll replace the 1 gm s w the new ysm 15 s BUT i fear the price of the new ysm is pretty astronomical and it may not fit in my smll space. i have the service and parts manuals for the 1 gm10 but havent had much success in yanmar sending me the parts manual for the ysm so i can check install dimensions, seacock diameter, etc... all questions to yanmar now get the stock reply of thanks for your inquiry 'contact your local dealer ' with a link to an unintelligible map that is useless for 'finding my dealer..' (o, for the olden days when i could call mack boring or torrensen , and get larry berlin to answer my questions... ) but being an oldfashioned sailor, i like to spec things out for myself before i 'talk to my dealer...' . stay tuned, as the saga continues...
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