Yanmar 2gm20f stem seals

[Voyager1]

1. Has anyone replaced stem seal without removing the head on a Yanmar 2gm20f. Is it reasonable possible? My repeatable diesel mechanic where I get my Yanmar part thinks it is if you are at TDC when replacingthey don’t work on marina engines but have done it a vehicles.

2. My Yanmar 2gm20f has the cast hole on the clutch housing for matching mark. I have the manual hand crank and turn the handle until it gets tight, check for matching mark with no luck, continue to inch along, still can not find it. Did this about a dozen times. Any suggestions, I am expecting to see a 1T and 180 degrees out a 2T. Am I missing something?

thanks

 

[sesmith]

That might work if you brought each piston to tdc so long as the engine didn't rotate while working on it . I've done plenty of automotive engines without pulling heads, but in all cases I used an air pressure setup to pressurize the cylinder to keep the valves up. You also have to consider what you will use to compress the valve springs. As easy as it would be to pull the head, I think I'd go that route myself. That way, you could also get a good look at the valves and guides.

 

[kloudie1]

I think that the mark is only visible with the starter removed. There should be a stamped line then 15 degrees after that the 1T and 2T marks. I don't know what the deck height is, so I can't know if the valve will fall down far enough to prevent re-installing the keepers after replacing the seals.
EDIT After looking in the manual, the valve should fall about .040" at TDC .. seems like you could do it, Worst case might be that you'd have to get 2-3 ounces of oil into the cylinder through an open valve then rotate by hand to hydraulic lock and hold it there by hand until ya get the keepers back on.. then decompress and eject the oil.. be sure to have the kill knob pulled so there is no chance to have an arm breaking "pop".. let us know how it goes.
Yanmar-Marine-diesel-engine-2QM20H-3QM30H.pdf (sailboatowners.com)

 

[Charles Erwin]

I have top clearance at .027 - .035. GM shop manual at p 2-21. By the way what is the reason for stem seals only?