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Old 29-07-2014, 19:31   #1
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Yanmar YSM12

ok I have one of these that needs a slight rebuild, previous owner blew out the piston lands with easystart but the price was right and it's headed for a glass H28 like many more before it, have a few questions, while it sits glaring at me from the shopfloor, for anyone who's run the YSM 12 before,
1/ what is the optimal altenator conversion for these to up the output?, after something that doesn't soak up most available power before it gets near the propshaft but certainly more than the std 30amps or so
2/ have these ever or has anyone ever tried running them via a heatexchanger,(or for that matter keel cooling) aware of the need for a 2nd circ pump which may well need to be centrifugal, and perhaps knocking together an alternate thermostat housing (automotive t/stats retail here for a hell of a lot less that the std yanmar part)
3/ The oil filter style/ mechanism, is there an adaptation of this to a remote mount cartridge filter?, I know these engines have done a zillion hours in std form but it seems a pretty Neanderthal means of supplying clean oil
Appreciate your answers
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Old 10-12-2014, 17:51   #2
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Re: yanmar YSM12

Bump.. gotta be someone who's played with these
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Old 13-12-2014, 16:08   #3
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Re: yanmar YSM12

Had a ysb8 raw water cooled of course, yes the filter system is a little on the crude side, but like you said these ran for a zillion hours with just that system. The whole thing is about simplicity, so forget the fresh water cooling, the filter system, yeah, I suppose you could go up a bit in amperage for the alternator, but those Hitachis, with everything built in-- again simplicity and much more load would as you say draw off too much power. These are loose engines, dirty, not efficient, but built for reliability, with the operating temp of 150 degs. Fahrenheit changing to fresh water with a more efficient operating temp, might work. I switched to a used 1gm10 when I found out I couldn't rebuild it.
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Old 27-12-2014, 09:58   #4
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Re: Yanmar YSM12

What I've learned:
The YSM series is equipped with a Hitachi LR135 alternator, putting out 35 amps max.
Later Yanmars have LR 155's with 55 Amps. The LR 135 and 155 are physically similar but the terminal ends are different, ring vs spade. While putting out Maximum amps, the 55 amp will draw approximatly 5/8 horsepower more than a 35amp. Note, this is not 5/8 HP total, but 5/8 difference. IIRC its about 1.5 HP total, but I don't remember ecaxtly.
Note this difference only occurs when the battery is discharged enough to accept 55 amps through the Hitachi regulator. In a "normally" discharged battery, the 55 amp will not really draw 55 amps, and will draw about as much as a 35 amp in similar conditions. So why use the 55? It is slightly less expensive, and enables you to use a less expensive electric tach rather that the magnetic tach on the 35. In "normal" day to day use, you should'nt notice a difference, especially if you install a solar charger to keep the batteries topped off. If you are planning a High output system, the Hitachis are too delicate to run for hours at max output. IMHO if you are planning a smart regulator installation, invest in another alternator. If you are planning "typical" 28' weekend usage, the Hitachi alternator/regulator should be fine, especially if you add a solar panel.
Lou
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Old 27-12-2014, 10:18   #5
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Re: Yanmar YSM12

Sorry, I only saw question 1.
The YSM with minimal care will last nearly for ever. If you plan too many modifications, you rapidly approach the cost of a repower. 2 Years ago, the cost to rebuild my 78 YSM 12 was about $4500 with a 90 day warranty. A new Beta 14 was about $5,000 with a 2 year warranty. The beta had a 70 amp, alternator, fresh water cooling and a remote oil change system. Any modification you make will not increase the life expentancy enough to pay for itself.
It will be easier and cheaper to change the oil more frequently than to modify the oil filter system. It will be easier to set up an ac inverter to heat water, or a propane powered on demand system, than to modify the 12. The YSM12 is a reliable, simple 38 year old motor. But it is a 38 year old motor. After a while you begin to like the Old Thumper!
Lou
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Old 27-12-2014, 10:45   #6
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Re: Yanmar YSM12

Regarding the alternator, could have it modded to use an external regulator? That will provide a lot more output. You can install a field on-off switch if you put a larger alternator on it.... even up to 100 amps. If you need to move the boat during the first 15 mins of startup, just switch the alternator off.
There are a lot of aftermarket heat exchangers around, if you really want fresh water cooling it could be done. As you mentioned you need another pump. MY YSM30 had an external tank/heat exchanger that wasn't attached to the engine. It was a Yanmar branded unit.
Can you obtain the piston/parts to rebuild it? It's got to be pretty simple on that engine. One cylinder right? Someone tried to get into Illia28's knickers on that $4500 price!
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Old 27-12-2014, 11:23   #7
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Re: Yanmar YSM12

yes you can modify the hitachi for an external regulator, but the hitachi is not made for running at full output fpr a long time. Prolly not worth it.
The price was for a full rebuild at a Yanmar dealer, parts and labor. Actually typiacl prices for NY Metro area. The labor rate at the Marina is $100/hr!!!
I try to d0 as much as possible myself.
Lou
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Old 27-12-2014, 20:01   #8
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Re: Yanmar YSM12

before you spend any money on it check that the oil pump is able to supply oil pressure,this is the most common fault on these engines,resulting in worn crank pin bearings,not quick start as you might think.

I have just rebuilt a ysb 8 which is basically the same engine.

workshop manual here
http://www.devill.net/Documentation/Yanmar/YSM-8-12.pdf
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Old 27-12-2014, 21:51   #9
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Re: Yanmar YSM12

guess the original poster got what they wanted.....
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Old 28-12-2014, 10:40   #10
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Re: Yanmar YSM12

Quote:
Originally Posted by lillia28 View Post
yes you can modify the hitachi for an external regulator, but the hitachi is not made for running at full output fpr a long time. Prolly not worth it.
The price was for a full rebuild at a Yanmar dealer, parts and labor. Actually typiacl prices for NY Metro area. The labor rate at the Marina is $100/hr!!!
I try to d0 as much as possible myself.
Lou
Yeah... I wasn't knocking your decision.... just that price they gave you. I would probably repower myself as I always hated that rough little Yanmar even when new!
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