1960 10 hp johnson problems

[plumbduck]

i have a 1960 10 hp qd 21 it has ran good for a long time but recently started "coughing" while running wide open. now it is also starting to do it at idle. i have gone through the carb but cant find anything wrong. i have also tried adjusting both needles but it doesnt seem to matter. so anyone have any ideas?

 

[oldboat1]

could be carb, but could be ignition. Check for spark with a spark tester, and check compression while you are at it. If and when you have spark, move to fuel/carb issues if still running poorly. Those needles take only slight adjustments. Seat both of them lightly, then back out the top one 1 1/2 turns, and the bottom one about 3/4 turn. Those are initial settings, subject to adjustment when the motor is warmed up. If ignition OK, motor should pop at those settings and want to run.

 

[HighTrim]

Are the coils original? If so they are likely now cracked and junk. They often fool you into believing you have a fuel delivery issue. You may have an ignition miss.

Also, The clutch dog may be jumping in and out of gear, fooling you into believing you are hearing a cough.

 

[F_R]

Clutch dog was the first thing to come to my mind. Most people describe it as feeling like they hit an underwater obstruction. Watch the shifter lever for jumping when it "coughs".