Re: ’73 18hp OMC will not idle Home › Forum › Ask A Member › ’73 18hp OMC will not idle › Re: ’73 18hp OMC will not idle johnyrude200Replies: 782Topics: 186 August 14, 2017 at 12:34 am #63026 How would that cause the motor to run lean? If anything, it would run rich or not at all because it can’t breath. The motor runs totally fine at anything above 1/4 idle.