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rustyballast 08-14-2011 07:44 PM

O'Day 30 Yanmar YSB12
This past February after a good sail in good wind my son and I were getting ready to put the boat in the slip. As the wind was blowing hard I had to get on the engine hard to maneuver. Why backing off the throttle I heard a sickening metal sound and the engine stopped. The O'day cruised into the dock at a fast walking speed. The crunch sounded bad and I expected a hole in the bow. As it turned out, there was a little divit and nothing else. The old O'Day was impressively tough.

Over a matter of three months my son and I pulled the engine and rebuilt it. It had blown a head gasket and the rocker arm nuts were so loose it dropped the push rods. It now has a new cylinder sleeve, piston, rings, rod bearing, wrist pin bushing, seals, etc. It is back in the boat and running well. I was lucky. Parts and cost of the boom truck totalled $800.

The boat has a dripless seal. It was an exciting moment when I learned how those things work as I moved the engine away and the boat started to flood.

I have one remaining problem. It seems that the motor now wants occasionally to not stop and if left at an idle in neutral will increase in speed. Not all the time but occasionally. Any ideas? It starts easy first try. Runs fine under load.

ermalexan1 03-02-2012 08:08 AM

YSB12 parts

I need to restore my YSB12 too.
The piston and the liner are damaged.
Could you please indicate me where did you buy the differrent parts for your engine?
Thank you in advance.

Best regards,

from France...

Faster 03-02-2012 11:07 AM

These guys are just across the Channel:

Marine Engines. Sales, Spares, Service and Repair, French Marine Motors - UK

Here's a list of European Yanmar distributors:

Yanmar Europe | List of distributors

Though there's a French listing, their site only mentions Cummins.. Good luck!

rustyballast 03-03-2012 09:40 AM


J'ai pu acheter toutes les pièces du fournisseur suivant:

Torreson Marine, Inc.
3003 Lakeshore Dr.
Muskegon, Michigan 49441

Sailboat Supplies, Engine Parts and Boat Parts

Le coût total pour toutes les parties était de 407 $

J'ai fait un outil spécial pour enlever le liner à l'aide tige filetée et un bar à plat. Je peux vous envoyer de nombreuses photos.

On m'a dit que la culasse n'est pas disponible.

Où en France?

Mon français n'est pas trop bon. :o

The total cost for all parts was $407. I made a special tool to remove the liner using threaded rod and flat bar. I can send you many pictures. I was told that the cylinder head is not available.

Where in France? My French is not too good.

rustyballast 03-03-2012 09:58 AM

Another note: Regarding the motor dying at idle turned out to be air in the fuel line. There was an old electric lift pump abandoned in place in series with the fuel line. With all air purged from the line, before removing the motor, it was not a problem. Once the line was opened however it became an issue. I removed the old lift pump and installed a manual prime bulb in location after Racor filters. After about 50 squeezes :laugher with the motor running all air has been purged and I have not had a problem since.

I probably need to find a new electric lift pump but have not found the time to research yet.

A year later the motor is still running fine. It starts first try even when very cold out. Down south here the boat stays in the water.

The valve backlash on this motor is adjusted like the valves on an old VW engine. The manner in which the motor is mounted in the boat leaves no access to periodically check valve backlash. I will fix this this summer. Valve backlash was the root cause of the motor stopping...they became so loose that the push rods literally fell out of the rocker arms. There were other issues as well as the motor had been in the salt for a number of years and cooling passages were plugging up with sea critters and unidentified crud. I cleaned all passages including those in the cylinder head.

I was told that the cylinder heads are no longer available. Fortunately mine was okay. They are quite heavy / crude so should be rugged.

ermalexan1 03-04-2012 04:56 AM

Your french is not so bad, maybe better than my english:)
Where did you learn it?
Thank you very much for your responses. I'm really happy to see that I would normally be able to repair my engine.
It's my first boat, I bought it last summer and I'm currently restore it.
It's a "Brin de folie" from Janneau.
I'm interested by your photos and the purchased parts list.
I can't reply to the personnal message because I'm a too young member.
I send you an email to your personnal email address.
once again, thank you very much.
I look forward to reading from you.

Sailingking22 05-18-2012 02:55 AM

Re: O'Day 30 Yanmar YSB12
Do you have any hints for cleaning the crud and sea critters inside the motor on a Yanmar that is still working okay, but overheating a little? Did you come across any tips while taking it apart that could be done while still installed? Or perhaps a solution to run through the system?

rustyballast 06-11-2012 07:07 PM

Re: O'Day 30 Yanmar YSB12
Geez... been busy so this is a reply to a really old post.

Yes. On that old YSB, if I remember correctly, you can remove a top plate from the block and it will reveal all the passages down around the cylinder and into the head. It would be a messy job but could be done provided that you have good access from above.

Make sure your water impeller and cooling lines are not the problem first.

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