Rought start idle

[Galvez83]

Maybe someone could help me understand what is causing this rough idle on start on a 5.7GS 2001 Wellcraft. So far i have replaced distributor cap, rotor, plug wires, spark plugs, coil, fuel pump, fuel filter and rebuilt the carb....no change. Boat starts fine but until you give it throttle the engine shakes and rocks. Once throttle is applied and removed the engine comes back without the shacking and rocking. I have inspected for loose wires and have found nothing. Can anyone advise where to look next or what would be the possible cause?

 

[alldodge]

Have you tried adjusting the idle stop screw?

 

[Galvez83]

Have you tried adjusting the idle stop screw?

The idle mix screws where adjusted prior. Are you referring to the one at the throttle linkage?

 

[cyclops222]

Find a mechanic who can inspect and clean a STICKY choke section and or Accelerator Pump of your carburetor. 2001 is way over due for carb maintenance of it.

 

[Galvez83]

Find a mechanic who can inspect and clean a STICKY choke section and or Accelerator Pump of your carburetor. 2001 is way over due for carb maintenance of it.

Carb was rebuilt trying to find a solution to the issue.

 

[ESGWheel]

Please confirm your start sequence is as follows or correct it as needed:

1. Key on (not start)
2. Stroke the throttle (in neutral) to full open then back to idle to give it a squirt.
3. Key to start > engine turns over as it should and starts running right away.
4. While it does run it shakes, rattles and rolls as if only running on 6 cylinders.
5. Stroke the throttle in neutral to partially open, RPM advances and engine smooths out.
6. Back to idle and purrs like a kitten.

Does this happen 100% of the time regardless of weather or if the 2nd or 3rd start of the day when the engine has been run for some time?
Also, if you did not advance the throttle after starting does it stall or will it smooth out in 30 or so seconds?