2000 Johnson 50 2 cyl., purchased used. Last owner had carbs rebuilt and motor winterized. My mechanic mounted motor, did link & sync and set idle (out of water on muffs) I found the motor would stall while docking in gear at low RPMs. I adjusted idle screw a few turns. Now motor in neutral runs at about 1,100 RPM. In gear it idles around 900, but some times still stalls. Any thoughts? I was considering trying a decarb spray.