9.9 Johnson coughing at high throttle

[wheresthefish]

hello, my 9.9 johnson is running pretty good except when i turn the trottle to high speed and back down to low speed it immediately makes a coughing sound like it is sick. i would think that it should just smoothly make the transition from high speed to low speed without making a coughing sound. does anyone know what could be the problem. i did change out the carb to a 15 hp carb of the similiar year. my motor is a 1992. thanks for all the help!!!

 

[iwombat]

Re: 9.9 Johnson coughing at high throttle

That 15hp carb is probably the issue. It's got a larger throat and bigger jets. In order to run it, you'll need to match it up with a 15hp exhaust.

 

[wheresthefish]

Re: 9.9 Johnson coughing at high throttle

i checked the parts catalog and the exhaust tubes are the same part. must be something else. any other suggestions. it only coughs at high speeds. at low speeds it doesnt do this.

 

[wheresthefish]

Re: 9.9 Johnson coughing at high throttle

i checked the part numbers for the exhaust tube and they are the same. it only coughs at high speeds at low speeds it doesnt do this. any other suggestions? thanks again for the help.

 

[BoatBuoy]

Re: 9.9 Johnson coughing at high throttle

Interesting that you didn't mention the 15 hp carb replacement on the other thread when telling about the carb and the loud noise.

 

[wheresthefish]

Re: 9.9 Johnson coughing at high throttle

these are two totally different motors with their own issues. can you recommend something for this issue. please help.