YSM-12 Air & Oil Filter

[Bud22569]

My boat has a 1979 Yanmar YSM12 engine. I have rebuilt this old engine and would like to do my best to protect it. The engine's original configuration included an air intake silencer (no air filter) and a mechanical oil filter (a set of plates that you rotate manually).

I know that these old engines seem to have lasted for many years with this filter configuration. However, this seems like a significant weakness to me. Have any of you YSM owners come up with improvements for these two filter weaknesses? Perhaps a K&N canister filter would fit where the silencer is now installed. I have not come up with any ideas for the oil filter except for turning the filter plates frequently and removal for solvent cleaning every 25 hours of operation.

Any ideas are appreciated.

 

[Hermit Scott]

I put a john deer canister over the intake. It pretty much fits. I also rebuilt my YSM12 last year. I have been running synthetic oil in it since after I broke it in (about 5 hours).
The oil filter is troubling, I thought of fabricating an insert that fits into the oil filter cavity that has O-rings around it to chanel the oil correctly to an external. But I just stopped caring, considering that it ran fine for 30 years with regular oil and probably a healthy amount of neglect.
I think your approach to cleaning the filter every 25 hours is probably the best approach. BTW what is your start up oil pressure and your operating oil pressure once it's warmed up?

 

[Bud22569]

Oil Pressure

I have not measured the oil pressure yet. I have the gauge ready but have not installed it. I had oil pressure problems when I first bought the boat. New oil pump parts solved that problem. With new bearings the oil pressure idiot light clears while the engine is cranking.

Before rebuild, the compression was so bad the engine required heat help from a blow dryer in the air intake to start when ambient temp dropped to 60 F. The cylinder liner, piston and rings were all replaced as part of the rebuild. With the rebuild it is hard to start when the ambient temp drops to around 40 F. It will start, it just isn't easy. Does yours have cold start issues similiar to mine after rebuild? I wish Yanmar would have included a glow plug with this engine.

I did not do anything about testing or rebuilding the high pressure fuel pump. I don't know if the high pressure fuel pump is contributing to the cold weather starting issues or if this is just the way this engine is about cold weather starts.

 

[Bud22569]

I put a john deer canister over the intake. It pretty much fits. quote]

Do you have a part number for the John Deere canister? Did you fit it over the silencer or replace the silencer with the canister?

 

[Rob19574]

I think the best thing to do re oil would be a quick oil change or even just pump out a quart and replace with new. Cheap and easy enough.

I had mine rebuilt about 6 seasons ago and still runs fine. My head gasket went last summer and it leaked water externally. No damage internally. I pulled the head myself to replace the gasket and notice a hairline crack in the new liner. It was running fine with this crack and I'm not sure how long it was there...I had the liner replaced on the rebuild. I called mac boring and their specialists told me to put it back together and let her run as is. He told me the YSM engine was so over-engineered for its time that as long as they don't overheat and get their oil - your fine. It is noisy and underpowered but I could live with that.

 

[sailaway78]

Play with the throttle settings

On many of the Yanmars, it is necessary to find their sweet spot for a cold weather start. I have had a 2QM and a 3GM. They would both start almost instantly in warm temps, but both were a little difficult to start in colder temps. Then I learned to mess with the throttle settings, and things got much easier. The 2QM would be ver difficult to start when cold, till I learned that it wanted full throttle to make it crank better. The 3GM requires about 1/4 throttle to start easily when cold. Experiment with it a little bit, and you will probably find where it wants to be.

 

[Hermit Scott]

Fonda-Go to Lowe's in their lawn and garden. There is only one that I have seem, it is about 6" long and about 3"diameter. I took the silencer off, I don't think it's necessary with a filter.
They are noisy and underpowered for sure. If I could eliminate one of those it would be the noise first.
Fonda-the reason I ask you about the oil pressure is these engines have a design flaw. The oil pump shaft rides on the aluminum casing. After 30 years this can cause a serious drop in pressure even witht new oil pump parts. My oil pressure is 30psi at start and 22 psi when hot. The manual says it's supposed to be around 55psi.
The idiot light and alarm shuts off at 1 lb or so pressure but the engine will fail at that pressure. Many people have reported engine failure of rebuilt YSM12's due to lack of oil on the mains, with in a year of rebulding. Put a pressure gauge on it and at least see where you are. The good news is you can have the case rebushed by a good machine shop but the tolerances must be VERY tight. I am not going to worry about it unless my oil pressure drops below 20. Then I will rebush the case and replace all the oil pump parts.
Easy-you had a 2QM15 right?
My engine starts easily no matter what. I put it full throttle or almost full and 1/2 second cranking starts it. It is also easy to hand start.

 

[Patrick17430]

On many of the Yanmars, it is necessary to find their sweet spot for a cold weather start. I have had a 2QM and a 3GM. They would both start almost instantly in warm temps, but both were a little difficult to start in colder temps. Then I learned to mess with the throttle settings, and things got much easier. The 2QM would be ver difficult to start when cold, till I learned that it wanted full throttle to make it crank better. The 3GM requires about 1/4 throttle to start easily when cold. Experiment with it a little bit, and you will probably find where it wants to be.

Are you refering to the throttle handle itself at the helm or an adjustment at the motor ?

 

[Bud22569]

Fonda-Go to Lowe's in their lawn and garden. There is only one that I have seem, it is about 6" long and about 3"diameter. I took the silencer off, I don't think it's necessary with a filter.
They are noisy and underpowered for sure. If I could eliminate one of those it would be the noise first.
Fonda-the reason I ask you about the oil pressure is these engines have a design flaw. The oil pump shaft rides on the aluminum casing. After 30 years this can cause a serious drop in pressure even witht new oil pump parts. My oil pressure is 30psi at start and 22 psi when hot. The manual says it's supposed to be around 55psi.
The idiot light and alarm shuts off at 1 lb or so pressure but the engine will fail at that pressure. Many people have reported engine failure of rebuilt YSM12's due to lack of oil on the mains, with in a year of rebulding. Put a pressure gauge on it and at least see where you are. The good news is you can have the case rebushed by a good machine shop but the tolerances must be VERY tight. I am not going to worry about it unless my oil pressure drops below 20. Then I will rebush the case and replace all the oil pump parts.
Easy-you had a 2QM15 right?
My engine starts easily no matter what. I put it full throttle or almost full and 1/2 second cranking starts it. It is also easy to hand start.

Thanks. I'll check at Lowes.

I did not realize that the oil press idiot light came on at such a low pressure. I will install the gauge when I put her back in the water. She is out for a bottom job, new thru hulls and seacocks. I don't plan to launch until mid-March.

 

[sailaway78]

The throttle handle itself

Don't mess with the throttle adjustment, just try giving the throttle some advancement when it's cold. Different positions. Took several tries to figure out what the 3GM liked, but sure makes starting much easier.

 

[Bud22569]

My engine starts easily no matter what. I put it full throttle or almost full and 1/2 second cranking starts it. It is also easy to hand start.

Hermit, how low of an ambient temperature have you cold started your engine?

 

[Hermit Scott]

Unbelieveably cold for Texas! Down near 50 degrees F.
I am heading down there in the morning to do a little storage prep. Can't really call it winterization, there really is no winter. But it's cold enough we probably won't enjoy it for a while.