Erratic idling

[KDean]

I have a 1999 Johnson 150 Ocean Pro. Motor runs great, but after it runs for about an hour when you try to idle, it will idle a few seconds and then suddenly increase to about 4000 rpm's without moving the throttle. The only way to bring it down, is to turn off the motor. When you restart, it will idle a couple of seconds and then suddenly increase rpms again. If you let the engine cool for about an hour, it will idle fine. Have had mechanic's clean the carbs. They have also replaced the fuel pump. So far have spend about $1800.00 in repairs and problem is still not fixed. Any help would be greatly appreciated.

 

[Will Bark]

Gurus will chime in but it sounds like your motor starts to run lean which will increase the rpms but will also damage the engine, let others chime in to give you advice on how to fix t. Good luck