1983 470 merc run on

[fmalott]

when i shut the motor off it does the dreaded run on what should i look at i rebuilt carb at the start of season i'm pretty sure it's clean i soaked and cleaned all passeges with wire to make sure i got all the crud out new needle and seat so what usually causes this is it timing maybe i did the alternator conversion also

 

[Don S]

Re: 1983 470 merc run on

The two most common reasons for run on, is high idle rpm, and an immediate shut down of the engine after a hard run.
Idle rpm should be 650 -700 rpm. Let the engine idle for a couple of minutes after coming off plane, to burn off excess fuel from slowing down, and allow the engine to cool.

 

[fmalott]

Re: 1983 470 merc run on

you hit it right on Don S. both times it did it on the weekend was after a hard run i will pay more attention next time is this common for the older motors or do newer one do this also