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Old 23-12-2023, 19:53   #1
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Hi From Down Under

Hi to all,


I am 62 years young and my son is 28.


He recently decided to get into sailing and bought a Brother 25 sailing yacht.
We have played about in the local waters off Tannum Sands, Queensland, Australia where we live.


The yacht is great but when we bought it we were told that the inboard motor doesn't run but it came with a 9.8 outboard so we use that for now.


The previous owner said it turns over but will not run.


We have turned the key but it seems to be seized or at least will not turn over.



We decided to look at the inboard motor and it is a Yanmar YSM12.


I have found a service manual for it but thought I would rack users brains for a possible starting point for the service.


I have worked on lots of engines in my time but this is the first diesel inboard.


If this post is in the wrong place, I apologize and please feel free to move it or let me know where it should be.


Thanks in advance.


Greg.
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Old 23-12-2023, 20:06   #2
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Re: Hi From Down Under

Welcome aboard Greg,

OK, the YSM12 is long on the tooth but there isn't an easier old marine diesel engine to rebuild and many people have cut their DIY teeth on these engines. Enough aftermarket parts are around to keep the engine going. About the only deal breaker is the oil pump if it is badly worn. While the oil pump can be fixed, it can be a frustrating and expensive exercise.
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Old 23-12-2023, 23:03   #3
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Re: Hi From Down Under

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Originally Posted by Wotname View Post
Welcome aboard Greg,

OK, the YSM12 is long on the tooth but there isn't an easier old marine diesel engine to rebuild and many people have cut their DIY teeth on these engines. Enough aftermarket parts are around to keep the engine going. About the only deal breaker is the oil pump if it is badly worn. While the oil pump can be fixed, it can be a frustrating and expensive exercise.

Hi and thanks for the reply,


How would you suggest I begin on this service. I literally have no idea where to begin.


I assume getting the motor to turn over would be number one.


I have seen a video of a service on a motor that was left to the elements for 20 years and that one ran after a clean up, so I assume this one is serviceable.
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Old 24-12-2023, 01:36   #4
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Re: Hi From Down Under

I would take the injector out and pour a couple of spoon fulls of diesel down into the cylinder then go and have Christmas.

Gently working a breaker bar on the crank after a few days may create some movement, but don't go crazy. If not, pull the motor and take it home to disassemble.

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Old 24-12-2023, 19:31   #5
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Re: Hi From Down Under

Gregted I wonder if this YSB12 on Facebook has the same footprint. The seller needs to knock a 0 of the price, but it could be an easy swap over to a working engine. Well as easy as manoeuvring 130kg on a tight space can be.
Cheers
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Old 24-12-2023, 20:56   #6
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Re: Hi From Down Under

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Originally Posted by Fore and Aft View Post
Gregted I wonder if this YSB12 on Facebook has the same footprint. The seller needs to knock a 0 of the price, but it could be an easy swap over to a working engine. Well as easy as manoeuvring 130kg on a tight space can be.
Cheers

Thanks for that link. If we have too much trouble, that may be an option.
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Old 24-12-2023, 20:57   #7
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Re: Hi From Down Under

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I would take the injector out and pour a couple of spoon fulls of diesel down into the cylinder then go and have Christmas.

Gently working a breaker bar on the crank after a few days may create some movement, but don't go crazy. If not, pull the motor and take it home to disassemble.

Pete

Thanks Pete, We will do that when we get back to the boat after Christmas.
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Old 25-12-2023, 15:02   #8
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Re: Hi From Down Under

It might be worth paying for a diesel mechanic to come and have a look.
That should narrow down what the issues are.
You can then decide whether to try to fix them yourself or pay for an expert to do it.

You could ask around the yacht club to see who they recommend.

You could also look at doing an RYA Diesel Course.
Just check that it includes dismantling and reassembling an engine during the course (mine did).
Unfortunately it doesn’t look like there’s anything in Gladstone so you’d have to travel.
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Old 26-12-2023, 02:03   #9
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Re: Hi From Down Under

Quote:
Originally Posted by ChrisJHC View Post
It might be worth paying for a diesel mechanic to come and have a look.
That should narrow down what the issues are.
You can then decide whether to try to fix them yourself or pay for an expert to do it.

You could ask around the yacht club to see who they recommend.

You could also look at doing an RYA Diesel Course.
Just check that it includes dismantling and reassembling an engine during the course (mine did).
Unfortunately it doesn’t look like there’s anything in Gladstone so you’d have to travel.

Hey Chris,


The idea of a diesel mechanic having a look sounds like a good idea.
After Christmas settles down, I might pour some diesel down the injector and see if I can turn it over.
If it doesn't start, that will be the limit of my skills and advice given so we'll see.
Famous last words, What's the worst that can happen.

I will have to look around the yacht for the crank handle.
The last owner didn't mention it but I's sure it's there somewhere.
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Old 26-12-2023, 03:14   #10
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Re: Hi From Down Under

The Yanmar marine engine Facebook page is a very good resource. You can search the pages for all references to your engine, may also be service manuals etc in the files section
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Old 26-12-2023, 03:59   #11
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Re: Hi From Down Under

PM me if you need a pdf copy of the YSM service manual.

One issue with the YSM (& YSB & YSE) is the horizontal cylinder. If left sitting for a long period, any condensation that collects in the cylinder does not drain down, rather it sits on the bottom surface of the cylinder against the rings and given time, rusts the rings to the cylinder wall. The rust can be broken with diesel (or oil) in the cylinder and gentle rocking with the crank or the PTO pulley.

This is a very difficult engine to kill!
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Old 26-12-2023, 13:53   #12
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Re: Hi From Down Under

@ Greg:

Just because you've no experience now, with working on diesel engines, doesn't mean you would be unable to learn, and you'll save heaps of $$ better spent on fun. The guys here are generous with sharing their knowledge, and guided a lady skipper here through a complete rebuild which was successful. None of them was born knowing all of what they know now.

Wotname, above, has a long history of such.

Ann
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Old 27-12-2023, 16:12   #13
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Re: Hi From Down Under

Quote:
Originally Posted by Wotname View Post
PM me if you need a pdf copy of the YSM service manual.

One issue with the YSM (& YSB & YSE) is the horizontal cylinder. If left sitting for a long period, any condensation that collects in the cylinder does not drain down, rather it sits on the bottom surface of the cylinder against the rings and given time, rusts the rings to the cylinder wall. The rust can be broken with diesel (or oil) in the cylinder and gentle rocking with the crank or the PTO pulley.

This is a very difficult engine to kill!

Thanks for the offer and I will send a PM for that manual. I have found a copy of a scanned manual. Some of the pages are at 5 degrees off center but if I hold my head just right, I can work it out.



Thanks to everyone for the response to my questions.


We went out to the Roberts 25 yesterday and the injector came out easily, and it was not blocked, so win no 1.

We syringed 50ml which is close to 2 tablespoons into the injector hole and then attempted to turn the motor over with the switch and no go so then I clamped on the crank starter shaft with a stilson wrench until I started to mark the shaft but no glory there.

We did notice that the previous owner has disconnected the water intake to the water pump but we are hoping that he did this because the pump leaks and he didn't attempt to run it without water.

I also pulled the dipstick and noticed the engine oil was a grey sludge which should mean water in the sump, so I guess we'll have to syphon out the sump oil and replace with some clean stuff.

If we have to pull the head off, at least that will give me the opportunity to replace the head gasket which may be the source of the water in the sump.

We'll leave the diesel sit in the combustion chamber for a week or so and head back out for another go. It's only a 5 min drive for me and I'm retired so no biggy.

Will certainly be interesting to see how the Roberts motors with the internal motor.
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Old 27-12-2023, 18:26   #14
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Re: Hi From Down Under

Hang on a moment.

You're right about the water in the oil, and it is going to be difficult to "suck it out" because it is an emulsified mess. [We always run the engine before we try to suck out the engine oil for a change, to warm it and lessen its viscosity].

What story did the seller tell you about how the seizure was discovered? (I'm not understanding why one would remove the water inlet hose to the engine after it seized. Closing the through hull for the engine would stop water coming in.) Maybe my brain isn't firing on all cylinders today, but it sounds weird to me.

Nevermind, Wotname and skipperpete are both good mechanics here.
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Old 27-12-2023, 23:12   #15
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Re: Hi From Down Under

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Hang on a moment.

You're right about the water in the oil, and it is going to be difficult to "suck it out" because it is an emulsified mess. [We always run the engine before we try to suck out the engine oil for a change, to warm it and lessen its viscosity].

What story did the seller tell you about how the seizure was discovered? (I'm not understanding why one would remove the water inlet hose to the engine after it seized. Closing the through hull for the engine would stop water coming in.) Maybe my brain isn't firing on all cylinders today, but it sounds weird to me.

Nevermind, Wotname and skipperpete are both good mechanics here.

The seller didn't tell us it was seized. He told us it would turn over but not run but he may not have tried to start it for a length of time as he lived on board and rarely moved from his mooring.


I like your idea about starting the engine to warm the oil up but I was concerned about starting it with the sludge in the sump but that may be the only way to get it out. We'll see what can be done

I don't know why he removed the water intake from the water pump. I can only assume the pump leaked and he disconnected it and plugged it to stop water ingress.

It was still connected from inlet through primary debris trap and then plugged at the point where it should be connected to the water pump.

From the water pump outlet, it was still connected to the water jacket.

He had a small 9.8 hp outboard so I guess the inboard was not a priority.
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