Runs rough off idle

[Gmcgrath77]

Hi. New here just bought a 1990 Lowe 17’ with a 20hp johnson with a starter and a remote control. Got a great deal. Only prob is motor runs rough off idle. Starts decent when cold but great once warmed. I have cleaned carb, replaced fuel lines, cleaned tank, replaced plugs. Timing seems ok. In between 2 notch’s. I have tried to upload a video but I can’t. Email me and I can send. Greg.mcgrath77@comcast.net

 

[oldboat1]

Not sure which 20hp model you have, but think you have an idle needle, a primer, and a thermostat. The motor may be running cold, so you might check to be sure the t.stat closes letting the engine warm up (or warm up earlier than it does now), the primer should push some gas into the system for quicker starting, and the idle needle may be a little lean for easy cold starting. On combination, the issue likely tuning and starting technique.

Nice versatile motor!