Carburetor Adjustments
1978 Evinrude 9.9 and 15HP models
THROTTLE CAM ADJUSTMENT
a. Proper setting of the throttle pickup on the throttle cam is important for obtaining good overall running qualities together with the best possible fuel economy. Sometimes though, it is difficult to tell when the carburetor's throttle shaft first begins to move. You can make a simple tool to exaggerate this movement from an alligator clip and a piece of stiff wire.
b. Attach clip to end of throttle shaft opposite the cam follower linkage. See Figure 3-23.
c. Advance throttle grip until center of cam follower roller is within the raised marked area on the throttle cam. See Figure 3-23. At this point throttle shaft should just begin to rotate. If not, adjust as follows: Loosen two cam screws (see Figure 3-23) and adjust cam in or out as necessary. Tighten screws and check operation. Throttle shaft should start to rotate as center of roller aligns within the wide mark on the throttle cam.
d. Install air silencer base and cover with washers and screws.
LOW SPEED NEEDLE ADJUSTMENT
a. Start engine.
b. With motor at operating temperature, run in gear at slow speed (700-750 rpm) with test propeller in tank or on boat. Adjust low-speed needle until highest rpm reading and smoothest performance are obtained. Allow 15 seconds for motor to respond to adjustment.
c. Position low speed knob with pointer down, and replace on needle valve shaft without disturbing position of needle.
d. Adjust idle adjustment knob to allow motor to run at 600 rpm in gear. For neutral speed adjustment, see Section 6, "Adjustments."
Updated on: Wednesday, November 11, 2020