I have a 1979 CD27 with a ysm8 with an unknown amount of hours. Currently running sae 30 per yanmar recommendation.
The engine seems to always smoke a little, more under load or higher rpms. Smells like burnt oil to me. When I pull the dip when running, it seems like there is a lot of pressure in the crank I get a good oil spray. Under full throttle there was some smoke around the cylinder head, I don't know if there is a breather there.
The engine runs okay. Any suggestions? Can rings on this engine be changed relatively easily, maybe in situ? Or does the case need to be split to get to the big end of the conrod? Is this an engine that one can even get parts for for a rebuild? Suggestions welcome.
- AT
Worn rings on ysm8 yanmar?
Moderator: Jim Walsh
Re: Worn rings on ysm8 yanmar?
While it may have worn rings, if it runs and runs reliably, I wouldn't recommend doing anything to it. Let it smoke happily away. On these old engines, once you open them up, one thing leads to another, and soon they get expensive. Result is a very expensive old engine.
Smoking is likely caused by injectors or pump calibration. I've never seen a normally aspirated diesel burn sufficient oil to make smoke because they don't have vacuum like a gas engine which sucks oil into the cylinder. Sometimes they will smoke when you first start them due leaky valve guides allowing oil to leak down from the head, but that burns out after a minute or so. Injectors get clogged up or corroded, and instead of atomizing the fuel, dribble it out which can't burn cleanly. Pump calibration problems can also cause smoking.
However, once you remove the engine and open it up for honing and rings, you will find the injectors need rebuilding, or there is corrosion in the head or the pump needs a rebuild/calibration or valve guides are out of tolerance, head needs to be trued, mounts are worn out, you broke a head stud, etc., etc. Which is why I would do nothing so long as it starts and runs reliably unless you feel like taking on a mechanical project.
Steve
Smoking is likely caused by injectors or pump calibration. I've never seen a normally aspirated diesel burn sufficient oil to make smoke because they don't have vacuum like a gas engine which sucks oil into the cylinder. Sometimes they will smoke when you first start them due leaky valve guides allowing oil to leak down from the head, but that burns out after a minute or so. Injectors get clogged up or corroded, and instead of atomizing the fuel, dribble it out which can't burn cleanly. Pump calibration problems can also cause smoking.
However, once you remove the engine and open it up for honing and rings, you will find the injectors need rebuilding, or there is corrosion in the head or the pump needs a rebuild/calibration or valve guides are out of tolerance, head needs to be trued, mounts are worn out, you broke a head stud, etc., etc. Which is why I would do nothing so long as it starts and runs reliably unless you feel like taking on a mechanical project.
Steve
-
jfischgrund
- Posts: 97
- Joined: Jan 24th, '15, 18:50
- Location: Cape Dory 27
Re: Worn rings on ysm8 yanmar?
You can still get parts for the YSM8. I hope your problems with the engine are not a sign of something -- my 1981 YSM8, also in a 27', died this year, after a 'runaway diesel' episode. I hope you don't get there. There was another post here recently about someone else who had the same problem with a YSM8. I guess they are all in their 40s and showing their age.
.
.