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Old 29-06-2021, 08:40   #1
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Does a Yanmar 3YM20 have cylinder liners?

Does a Yanmar 3YM20 have cylinder liners?



I owned a 2gm and loved the fact that it has liners. I am considering a new 3YM20.

Rebuild kits for the 3ym20 are shown with cylinder liners for sale. But I see no mention of a cylinder liner in the Yanmar sales literature or manual.

I have yet to find a proper workshop manual for the 3YM20. Nor have I found proper exploded view parts images. Both would be appreciated if anyone has them.

THANKS!!!
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Old 29-06-2021, 17:44   #2
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Re: Does a Yanmar 3YM20 have cylinder liners?

I don't think they do. Suspect Yanmar went away from cylinder liners on their marine engines as they'd rather you buy a new engine maybe. Can send you a workshop manual for free if you PM me yr email. There is no mention of liners in the bore measuring section.
Personally I'd rather have a properly rebuilt 2QM15 than the 3ym20, as the 3ym20 has a pathetic duty cycle but thats just me. I would assume the 3ym20 is quieter & smoother tho being a 3 cylinder.

I would go for a Beta as a replacement new engine as the parts prices are waay cheaper than Yanmar & kubotas are good diesel engines as well. YMMV
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Old 29-06-2021, 18:06   #3
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Re: Does a Yanmar 3YM20 have cylinder liners?

Quote:
Originally Posted by cadmus View Post
Does a Yanmar 3YM20 have cylinder liners?



I owned a 2gm and loved the fact that it has liners. I am considering a new 3YM20.

Rebuild kits for the 3ym20 are shown with cylinder liners for sale. But I see no mention of a cylinder liner in the Yanmar sales literature or manual.

I have yet to find a proper workshop manual for the 3YM20. Nor have I found proper exploded view parts images. Both would be appreciated if anyone has them.

THANKS!!!
I agree with Compass 790. The service manual does not show liners but it does show two oversize pistons and how to match piston size to cylinder diameter which suggests to me the cylinders can be rebored.

AFAIK, the 2GM and 3GM were the last Yanmar small engines that had liners. The 2GM20 and 2GM30 did not have liners.
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Old 01-07-2021, 22:04   #4
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"they'd rather you buy a new engine" That sums up exactly how I feel.

Quote:
Originally Posted by Compass790 View Post
...Suspect Yanmar went away from cylinder liners on their marine engines as they'd rather you buy a new engine maybe.
That sums up exactly how I feel.
I can think of no other reason.
Sad.






Quote:
Originally Posted by Wotname View Post
...which suggests to me the cylinders can be rebored.
Not as helpful as cylinder liners. Especially in remote/developing locations. But better than nothing.





Quote:
Originally Posted by Wotname View Post
the 2GM and 3GM were the last Yanmar small engines that had liners. The 2GM20 and 2GM30 did not have liners.
Just as the 2GM was to the 2GM20, I was hoping the 3YM20 was a lined/sleeved version of the 3YM30 because they sure look alike.



(I realize 2gm preceded 2gm20)







Quote:
Originally Posted by Compass790 View Post
I would go for a Beta as a replacement new engine as the parts prices are waay cheaper than Yanmar & kubotas are good diesel engines as well. YMMV
I am considering both. (and a used bukh)
I would considering rebuilding the 2GM as simplicity and "SELF" serviceability is more import but they stopped making OEM parts in 2019.
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Old 01-07-2021, 22:06   #5
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Re: Does a Yanmar 3YM20 have cylinder liners?

Thank you two for the response and for looking it up.
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Old 01-07-2021, 22:41   #6
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3ym20 has a pathetic duty cycle

Quote:
Originally Posted by Compass790 View Post
.... Personally I'd rather have a properly rebuilt 2QM15 than the 3ym20, as the 3ym20 has a pathetic duty cycle....
I just went back to look for this in the documents and failed. But, I recall some oddball spec in the 3YM20 PDFs about duty cycle and that was one of my questions for a yanmar dealer last year. I explained, I rarely use the engine. if coastal maybe just get it warm while setting or pulling anchor. But, when we do NEED it we need it for numerous days, NON-STOP. I was assured it will of course run "days" non stop at max efficiency, just not at full throttle.

If you can, please enlighten me on the specs and what to look for. I am all ears. Thanks in advance. I just never believed it mattered. It is an engine on a boat. It should run all day if you need.
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Old 02-07-2021, 00:21   #7
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Re: Does a Yanmar 3YM20 have cylinder liners?

This is from the Yanmar installation manual. I was also aware of the 3 duty cycle ratings mentioned but could find no trace of it in the big book. From memory they were
Pleasure craft
Light commercial
Heavy duty commercial
But I think that they may have been the data to de rate the output for each category. Click image for larger version

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Old 02-07-2021, 03:32   #8
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Re: Does a Yanmar 3YM20 have cylinder liners?

Quote:
Originally Posted by skipperpete View Post
This is from the Yanmar installation manual. I was also aware of the 3 duty cycle ratings mentioned but could find no trace of it in the big book. From memory they were
Pleasure craft
Light commercial
Heavy duty commercial

But I think that they may have been the data to de rate the output for each category.
Those ratings also seem familiar, to me.


An interesting & informative article on duty cycles:
“Continuous Duty – A Different Perspective” ~ by Tony Athens [a Cummins engine specialist]
https://www.sbmar.com/about-seaboard-marine/
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Old 02-07-2021, 10:32   #9
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Re: Does a Yanmar 3YM20 have cylinder liners?

This site:
https://www.tradeaboat.com.au/news-r...-engine-review
says
"The engine has an A rating, or up to 500 hours of running per year with a maximum of five per cent Wide Open Throttle operation"
what the heck is 500 hr a year. I would never run 500 hours a year (unless i landed some grant doing plankton tows or something). But, what the heck does it matter if 500 per year vs 500 per month. One will do preventative maintenance based on hours.

(not that that is a good site but clearly they cut and pasted it from something)
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Old 02-07-2021, 10:38   #10
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Re: "they'd rather you buy a new engine" That sums up exactly how I feel.

I am considering both. (and a used bukh)
I would considering rebuilding the 2GM as simplicity and "SELF" serviceability is more import but they stopped making OEM parts in 2019.[/QUOTE]


I would try & find out if the 2GM has a tractor base engine. Most of those early Yanmar marine engines did AFAIK. There are tractor engine parts available from Taiwan of japanese quality for much cheaper prices. If you can find tractor parts go for the rebuild would be my choice.



Bukh DV20 is a sound engine although heavy, trouble is parts prices are probly worse than Yanmar impossible as it may seem.


Will PM you link to duty cycle report.



Sad alright how built in obsolescence pays, however technology changes rapidly as well.


BTW I think the article that Gordmay posted ( thanks GordMay )
sums what duty cycle means pretty good.
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Old 02-07-2021, 17:35   #11
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Re: "they'd rather you buy a new engine" That sums up exactly how I feel.

Quote:
Originally Posted by Compass790 View Post
I am considering both. (and a used bukh)
I would considering rebuilding the 2GM as simplicity and "SELF" serviceability is more import but they stopped making OEM parts in 2019.

I would try & find out if the 2GM has a tractor base engine. Most of those early Yanmar marine engines did AFAIK. There are tractor engine parts available from Taiwan of japanese quality for much cheaper prices. If you can find tractor parts go for the rebuild would be my choice.



Bukh DV20 is a sound engine although heavy, trouble is parts prices are probly worse than Yanmar impossible as it may seem.


Will PM you link to duty cycle report.



Sad alright how built in obsolescence pays, however technology changes rapidly as well.


BTW I think the article that Gordmay posted ( thanks GordMay )
sums what duty cycle means pretty good.[/QUOTE]



There is a 3GM industrial model , 3T-70B , I have one amongst my “to do” store of engines waiting for a heat exchanger. Lower rpm and hp by a long shot but basically the same engine with a different flywheel housing.... I put a 2 GM housing on it.
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