Buy Mercury Parts
Buy Mercury Marine Outboard Parts

Announcement

Collapse
No announcement yet.

40hp Mercury- 1998 running Rich

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • 40hp Mercury- 1998 running Rich

    40hp Mercury- 1998. This motor has the 60hp carburetors on it and the air intake baffles were off. Ran like a scalded cat. However, it was loud and idle was fast.

    This week, I put the air intake baffle/plenum back on. Idle is great, but the motor will not rev up like before and almost 4-strokes. Running Rich. I have not pulled the plugs yet to confirm, but pretty sure the high speed jets need to be changed out.

    From what I can find, the High Speed Jet is on the lower Port side of the carb, near the bottom of the bowl. When I pull the brass "screw" it is a hollow bolt with two holes in it. Is the size of these holes the Jet??

    There is no number on this to indicate what size the jet is.

    The plugs are wet and dark, almost black, but no carbon build up. Only ran it 2hr with with setup. Took the Air Plenum off, and the motor runs super- VERY fast.

  • #2
    The main jets are at the bottom of the bowl, they should be marked with their size.
    Regards
    Boats.net
    Mercury Outboard Parts
    MerCruiser Parts
    Force Outboard Parts
    Mariner Outboard Parts

    Comment


    • #3
      40hp running rich

      So, to access the High speed jets, I have to take the carbs off and remove the bowls?

      Any suggestions on how to "guess" what jet is needed?

      Comment


      • #4
        There should be a drain screw in the bottom of the bowl, the jet is behind that screw. The 40hp should have a 0.066 main jet, would be stamped 66.
        Regards
        Boats.net
        Mercury Outboard Parts
        MerCruiser Parts
        Force Outboard Parts
        Mariner Outboard Parts

        Comment


        • #5
          Changing jets????Why???What have you done??
          The only reasons is elevation and if the motor was bored out a BUNCH!!
          Running rich should be adjusted at the air screw.
          Then check for sucking air.

          Comment

          Working...
          X