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Weber Marine Carburetor Adjustments

Float Level

Measure the float level from the bottom side of carburetor top (w/gasket) to toe of float. Adjust by bending the flat hinge part between the float and the needle. Be careful not to put any pressure on the needle. The viton tip is easily damaged.

1 9/32″ 

Float Drop

The float drops so that the needle will open and allow fuel to flow into the float bowl. The important thing about the float drop is that it doesn’t drop so far that it allows the needle to bind open and yet drops far enough to allow enough fuel in. Measure as illustrated, from the top to the bottom of the float. To adjust bend the tab at the back side of the needle & seat. 2″

Accelerator Pump Adjustment

Back out the idle screw so that it doesn’t touch the throttle lever.
The throttle valves should be closed completely.
Measure the distance from the carburetor top to the bottom of the S link.

To adjust, bend the linkage rod that connects the pump lever to the throttle lever.


Accelerator Pump Adjustment

A – Rich
B – Lean
C – Leaner

The Weber marine carburetor accelerator pump lever has 3 holes. The standard position is to have the rod in the 1st (A) hole. If you are experiencing a bogging down on acceleration try placing the rod in hole B, then hole C.

Adjust Idle Mixture

  • Warm the engine to operating temperature.
  • Adjust the idle speed to manufactures specification.
  • Turn the idle mixture screws out about 2 turns to start with.
  • Use a RPM meter, or simply listen to the engine.
  • Take turns with each screw turning in 1/4 turn until the RPM starts to drop.
  • Wait a second between turns to allow the engine to catch up.
  • Turn the screw back out 1/4 turn.

If after adjusting the idle mixture your engine doesn’t idle very well, then you may have another problem. Be sure all of the idle vents and tubes are clean and clear. Remove the mixture screws and blow out the passage.

Updated on 12/15/2020

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