Bleeding a Yanmar 2QM20

This is pretty much an FYI post, as it took me a while to figure this out. This is NOT the procedure in the manual, but works a ton better!

Basically there are TWO places to bleed it, labeled here.


  • First, crack the screw labeled ‘1’ while hammering on the manual little pump handle. Once fuel with no bubbles comes out, crack it tight.
  • Then do the same to the nut labeled ‘2’. This one is not mentioned in the service manual for some reason! Once this is complete, you should be able to start and run the engine fine.




  1. Hi Matt, Happy to find your blog after your salmon fishing posts on SV Violet Hour. I too have a 2QM20 (in my 78 C&C 34) and wish I had seen this post just a week ago. I spent most of the day sunday trying to get my engine to start after cleaning my Raycor fuel filter. I eventually figured out how to get the air out, but it took a long time.

    • Hi, thanks for reading!

      Yes – it’s annoying hey? It took me hours and hours the first time round. Hence the post. The C&C 34’s a great boat!

  2. Yes, it was most frustrating. There is actually a short Yanmar user pamphlet on my boat that I eventually found which describes how to completely remove all air from the fuel system . If I recall correctly, It says to:
    1. open the screw you have labeled #2 and pump until fuel comes out, then tighten #2
    2. open the junction that at the fuel filter that goes to the fuel pump. Open what you have as #1 and pump until fuel comes out of #1, then tighten #1 and then tighten the junction at the filter.
    3. loosen the nipple where the fuel enters the injector, engage the decompression leaver, and turn the manual crank 20 times ( I don’t have a manual crank so i just turned engine over for a few seconds)
    4. tighten the nipple, disengage the decompression leaver and start the engine

  3. For 3., looking at the user manual now, I think this could be the nipple at the “fuel return pipe.” The nipple is just fore of the air intake. I’ll try and capture an image of the pamphlet when I get a chance.

Leave a Reply

Your email address will not be published.