Yanmar oil pressure

[Hermit Scott]

I have a YSM12 on my C30, as most of you know. I rebuilt it but i didn't rebuild the oil pump. I was reading the manual and saw that the oil pressure should be 35 to 50 psi. It runs at 30 psi. I ran it pretty hard the other day and when hot the oil pressure was at 20. I let it cool off, it's at 30 and at idle will drop to around 26 psi when warm. A little research in the archives reveled that the oil pump shaft is riding on the aluminum front casing and the casing wears out and lets the oil out there instead of goiing on the the engine.
There is a company that has a jig to bore out the hole and replace it with a brass bushing. I can try to have a machine shop I deal with do it but it may not turn out right. Because they will be drilling a round hole into an oval hole and they won't have a jig.
Does any one know who can do that for my YSM 12?

 

[Don S/V ILLusion]

I vaguely recall once suggesting to you to get the service manual for this engine. If you have, follow the recommendations therein to test the pump and seals before subjecting anything to the drill - tolerances are crucial here and without the manual, you are destined to cause more problems. By the way, are you losing oil and if so, to where?

 

[Hermit Scott]

I have the manual. Oil pressures in cars at 30 psi is fine. I didn't realize this was supposed to be so high. I should have looked.
The manual recommends replacing the front cover if it's out of tolerance.
I have read it is $1500. For less than that I can get a perkins 4-108 with 1100 hours on it. People replace the perkins with yanmars becasue they say they are half the size and the same hp.
I am not losing any oil. There are no leaks and it runs great. I notice if I run it too hard too long that I will get oil in the exaust. But There is no measurable loss on the dip stick. I only have 15 hours on this oil change though.

 

[Don S/V ILLusion]

30 psi or less at idle, particularly when the engine is hot, in the absence of any oil loss, is a non-issue. Even 20 psi is okay when hot as long as it is higher when not (hot).

 

[RAD88]

Oil Pressure gauge

I have a YSM12 on my C30, as most of you know. I rebuilt it but i didn't rebuild the oil pump. I was reading the manual and saw that the oil pressure should be 35 to 50 psi. It runs at 30 psi. I ran it pretty hard the other day and when hot the oil pressure was at 20. I let it cool off, it's at 30 and at idle will drop to around 26 psi when warm. A little research in the archives reveled that the oil pump shaft is riding on the aluminum front casing and the casing wears out and lets the oil out there instead of goiing on the the engine.
There is a company that has a jig to bore out the hole and replace it with a brass bushing. I can try to have a machine shop I deal with do it but it may not turn out right. Because they will be drilling a round hole into an oval hole and they won't have a jig.
Does any one know who can do that for my YSM 12?

I have a YSB12 but it has idiot lights on the dash. Is there an easy way to hook up an oil pressure gauge and is it possible to have the gauge and the idiot light as an added warning. I am also looking to hook up a tach, volt, water temp and fuel gauges to the new dash. Any ideas?

 

[Ross]

Re: Oil Pressure gauge

Any machinist with a vertical milling machine can put a round hole where he wants it to be.

 

[Allan12210]

Oil Pressure Gauge + Idiot Light/Buzzer

I don't have the YSM12 engine, so I don't know if the set up is the same, but I added an oil gauge to my 3GMF22 quite easily. There is actually a second tapped hole underneath where the existing sender is located (see the picture). There is a plug that is removed with an Allen wrench up there. I used an electric oil pressure sender to the proper gauge. You also need a metric to NPT adapter that was available at my auto parts store. I mounted my gauges outside next to the control panel. This was trickier. I have a lathe, so I was able to fabricate some screw on cap faces to protect the guages. They work quite well. I have Volts, Amps, Oil Pressure and Water Temperature. The idiot light/buzzer functionality is fully retained.

If you don't have the extra hole into the oil galley, you can install a small pipe "Tee" and use both senders. Remember to get the adapter so you can use the American threaded pipe parts. Same on the water temp sender.

Allan
H34 "Alchemie"
SF Bay

 

[zeehag]

hermit--you do NOT wantt the perkins anywhere near your boat---weighing in at 600 pounds, you will have an untrimmable squat and therefore pound the waves with your bows always and forever, not to mention you will never be able to check the oil---your engine room is waaay too small for the bruiser...also--the cost of replacing the small yannie with the bruiser includes stringer modifications---perkins does not bolt into a yannie place....i can see dollar signs flying all over the place in this mess....first the engine....then the tranny....then the stringer mods..dont forget the shaft and prop will require changing out.....and this is before the engine even goes into the boat--also--perkins engines drip oil --they always drip oil....english as opposed to japanese--go japanese....perkins is ok for formosa but is waaay tooo much weight fora c30...goood luck with the repairs in the yannie....

 

[Hermit Scott]

Any machinist with a vertical milling machine can put a round hole where he wants it to be.

The problem is where DOES he put the hole? The pump shaft is not in the center of the pump body(trocoid pump).

 

[Hermit Scott]

30 psi or less at idle, particularly when the engine is hot, in the absence of any oil loss, is a non-issue. Even 20 psi is okay when hot as long as it is higher when not (hot).

Why do you think it will be ok at 30-20 psi? Is it originally built to accomadate the pressure drop from a well worn engine from 35-50 down to 20 to 30? Even though this one is rebuilt, the pressure is as if it is well worn. I was concerned that it would lock up with that low of oil pressure. Other posts say their small yanmars locked up after rebuild but their pressure was at 7.
Rad88-the oil pressure light comes on if the oil pressure is lower than 4.266 psi. The operating range I am concerned about is 20 to 30 psi. I would put a gauge on it. As stated, you can put a T connector inline.

 

[Kabloona]

Hermit, I just read your post re: your YSM-12 oil pressure question in '08. Please see my similar post dated today, 9-5-'09. Did you have your pump rortor shaft hole bushed? Does the pump continue to draw up its own prime? What have you learned in the process? Thanks, Kabloona

 

[Hermit Scott]

I saw your other post first. I did not have the hole drilled or bushed. I have a machinist that can put a hole anywhere I tell him to. The problem is, if you have an egg shaped hole where did the center used to be. There is no gaurantee the egg shaped hole is worn evenly in any direction. Maybe I am looking at this the wrong way though. IF I had engineering drawings for that front cover with coordinates for that hole I MAY try it.
I have never had a problem with the prime on my engine. The only reason I researched it at all is I was looking through the manual and noticed the operating pressure was between 35 and 55 approximately.
I see you have done alot to the oil pump. What were the clearnaces like for the front cover to the rotor face? Did everything check out clearance wise?

 

[Kabloona]

Thanks, Kermit and all

Kermit, Rob, Rick, Alan, Porche, Eddie, Zeehag and all others who kindly responded to my "Yanmar YSM-12 oil pump doesn't self-prime" questions: I think I have solved the problem - at least for the time being!

After bench testing the oil pump w/ electric drill by setting the entire side of the engine (that contains all the oil pump/filter/pressure controller/ low-pressure sender, etc.) in a pan of oil at the working level (and at the working angle offset from vertical) and watching oil run out of the inner pump rotor shaft hole as soon as I stopped rotating it, I decided to have the shaft hole drilled and bushed for a second time. The project needed to be done better this time!

When I first had this procedure done (15 months and only about 65 running hours ago) I trusted the diesel machine shop to provide the guidance as to bushing material and tolerance for the new factory shaft I'd bought as a set with the two pump rotors. Big mistake! This time I did more reading and located another machine shop with an interest in my job. He could make the bushing out of marine bronze (not brass as before), and to a tolerance of .0005 - .0010 in. He did the job in 90 min., for under $100, and let me watch! Unlike with the first job, my finger felt no side-to-side play in the shaft-in-bushing fit when he was done. The pump now pulls up a ready prime on cold starting and runs at 60 psi, not the 18 it ran at before. The shop manual prescribes 35 - 55 psi !?

Of course, it self-primed and maintained oil pressure after the first bushing job too. But, with this one having tighter tolerance and stronger material, I'm cautiously optimistic. Thanks again to all for your thoughts and encouragement,

Kabloona

 

[Hermit Scott]

kabloona-how exactly did he drill it? Did he drill it from the back with a bushing as a guide or did he just put the drill bit to the material and start drilling?
I took pictures of the insides of my engine when I had it apart. I was looking at them last night and thinking about the oil pump and your prime problem.
Could you tell us what the name and number of the guy you used is? I would rather ship it to him than hope that someone who hasn't done it before can do it right the first time.

 

[Bud22569]

Hermit did you get an answer?

kabloona-how exactly did he drill it? Did he drill it from the back with a bushing as a guide or did he just put the drill bit to the material and start drilling?
I took pictures of the insides of my engine when I had it apart. I was looking at them last night and thinking about the oil pump and your prime problem.
Could you tell us what the name and number of the guy you used is? I would rather ship it to him than hope that someone who hasn't done it before can do it right the first time.

Hermit, did you ever get an answer to what machine shop did this work?

 

[Hermit Scott]

I did not but from what I can tell from kabloona's post, we don't particularly need the same machine shop he used. After looking at pictures of my engine while it was apart, on the back side of the oil pump casing, there is a larger round machined hole leading to the shaft hole. It should be no problem to locate the hole for the bushing, which has been my only concern all along with rebushing. You just have to find a machine shop that will take their time and do it right. That is getting a very tight tolerance on the rotor shaft.
I keep a close eye on my oil pressure, it dosn't seem to be changing so I am not worried at this point. Besides, if I kill this YSM I have a 2QM20 sitting in my shop I would then install.

 

[RAD88]

Hernit - can you post a few of the pics you have of the inside of the engine? I have the same engine.

 

[Hermit Scott]

Hernit - can you post a few of the pics you have of the inside of the engine? I have the same engine.

My wife was like "WTF are you doing putting an engine block in our oven?!"

 

[Benny]

What grade of oil are you using? As engines wear tolerances increase so a heavier oil may be needed. You can go up to a 20-50 SAE or add an STP additive to your oil to increase its viscocity. This should restore your oil pressure and quiet down the engine some. Please understand this is not a repair but a way of extending the operating life of a tired engine. If you are planning to or have torn down the engine then a proper fix would be in order.

 

[Bud22569]

Oil Press Gauge

Hermit, how did you go about installing your oil pressure gauge. Some questions that I have.

Did you install a pipe tee and run the idiot light sensor off one side and the press gauge off the other. The pipe thread does not appear to be non-metric NPT. Are you using a remote gauge with a pressurzied sensing line or are you using some sort of electronic configuration. Or did you just mount a gauge on top of the engine?

I need to install a pressure gauge and am trying to learn from other people's experience.