I took my 9.9 4 stroke 1996 Johnson out today. Everything was fine for 15-20 minutes. Then after slowing down the motor would not accelerate when I opened the throttle. When I had the throttle open it would knock and sputter, and only accelerate to about 1/3 of the power it normally would have. It was working fine at lower to medium speed ranges. When I turned the throttle all the way down it would also knock and sputter after a few seconds. When the motor is in neutral it did not have any issues no matter how high or low I had the throttle. I had the power pack, spark plugs and lower unit oil changed about a month ago. This is the first time using it since. Any suggestions on where to start my troubleshooting?
