2003 Johnson 25 hp Sputtering at half speed

[freeves]

My 2003 Johnson 25 has a sporatic reliability issue. Generally, it performs perfectly. But, on occasion when accelerating from stop, at half speed ,the engine starts to sputter and cough and will not engage to go at full speed. I have had the carburetor cleaned and when in for repair the symptoms did not appear either before or after on a water test for the mechanic to observe. Upon returning to my lake the original symptoms reappeared. When it occurs I stop the motor, play with gear shift, pump gas. Sometimes the symptoms disappear but at other times it takes some time which is frustrating. Please advise me of what the issue may be as I have not been able to determine the cause with my troubleshooting. Thanks.

[boats.net]

Could be an ignition misfire but would need to ignition and spark tested when it's acting up to find problem.

[cvtech1]

It might be something as simple as gas. I have had this problem on occasion and it was due to loose clamps causing air to get in the system. They will get loose often.

[JUST-IN-TIME]

if the primer bulb goes soft, you have a fueling issue