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Weber marine runs rich or Floods

  • Make sure the ignition system is up to par. Plugs, wires & distributor.
  • Check float level - while you are at it test the float for leaks.
  • Make sure the float isn't rubbing anywhere.
  • Move the float up and down by hand to see if you feel any catching.
  • Do you see any dirt particles on the bottom of the bowl - this indicates a dirty situation and a rebuild would be in order.
    • How did the dirt get there? Is there a fuel filter and has it been changed.
  • Test the fuel pump pressure and compare with the specification in the motors manual.
  • Viton tip on the needle & seat may be damaged by ethanol, or has dirt in it keeping it open too much. When adjusting floats do not put any pressure on the needle. It's a sure way of damaging the Viton tip.
  • I would suspect main jets size, but only if they were changed for some reason, or you are above 5,000 feet in altitude.
  • Same thing goes for the metering rods. They might be a problem if someone has changed them. They won't cause flooding, but can cause richness.
  • Look down the carburetor at idle. Do you see gas dribbling from the venturi?

Weber Marine Parts

Adjusting Idle Mixture Doesn't Change Anything

Be sure the idle RPM is correct. If the RPM is too high, then the idle circuit is bypassed.
This is indicative of either a vacuum leak, or something is not right in the idle circuit.
Unless the screws are scored that would not be the problem. Changing the screws will not change anything.
Check for a vacuum leak around the mounting gasket, intake and any vacuum line coming from the intake, or carburetor.
Follow all passages, blow through them to see if they are open.
Look closely at the small holes in the venturi. Some are idle vents and get plugged easily.
Make sure gaskets are not covering a vacuum passage.

After a rebuild and on the bench turn the idle mixture screws all the way in gently. The screws will get scored if you turn them in too hard.
Turn the screws out 1 1/2 to 2 turns which is a good place to start.
After the engine is warmed up and at idle RPM:
  • Alternating between screws, turn them in 1/4 of a turn, and wait for the engine to catch up.
  • Once the RPM starts to drop, turn the screw back out 1/4 turn.
  • The ultimate goal here is to get the engine to run smoothly at idle so turning the screws in and out a bit to get the best idle is OK.




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