Accessory Plug (cigarette lighter) wiring

I put mine off the battery terminal on the ignition switch. 
This has the " ignition" breaker button in front of it so you have the protection of that breaker.
I then ran it to the main ground wire. 

I put the socket connection off the "B" terminal.   This is where the 12 volt power comes into the Key switch.

That way you do not have to turn the key switch to run to use the power socket. 

When the switch is on the run position it is putting current to the electric choke, the coil and the distributor.

If you are using it before the engine has warmed up  then the current to the choke would cause that to open all the way. 

In my case I replaced the points with and electronic ignition and I don't think you are supposed to have that sitting there with current going to it and not running. 

In your case if you have points then you don't have those electronics to worry about. 

Maybe one of the pro's could weigh in on having power to the coil without the engine running. 

In my case I prefer to no have the key on unless it is running  because that will drain the battery.  It also will run the hour meter.  The person I bought the boat from had the stereo wired off the "I" terminal with the key in the run position.  This would run the hour meter.   I am sure that they ran up the hours while hanging out listening to the music.  But that is not your case. 

I don't worry about the Accessory plug being a drain as I plug something in, use it and unplug it.  Usually it is the inflator for tubes or the pump for fat sacks.