Idling questions for 3.0L

[Condor1970]

I finally got my 1989 Merc 3.0L engine running really good, and have a question about the idle. I installed a Pertronix II system, and it runs great, but noticed the idle seems a little low. It is idling about 600-625rpm on the gauge.

Because of this, it still idles, but tends to have that chugging sound like it may want to quit on me, yet it doesn't, it still runs. When it idles at this rpm, it also tends to get that increase in vibration on the mounts, which is noticeable, but not really a major problem imo. However, it would be nice if the idle was a little smoother. It gets smooth as butter when it is up around 650-700rpm.

I have the idle mix set exactly at 2 turns like the manual says, and the electric choke is also set and works fine.

So, what rpm should it really idle at?

Should I adjust the idle screw on the control arm on the side of the carb, or should I just leave it?

 

[81 Checkmate]

Take your throttle cable off and set the idle to 650-700 with the screw on the control arm.... Put throttle cable back on.......Smooth as butter as you say.......

 

[fishrdan]

It gets smooth as butter when it is up around 650-700rpm.

I have the idle mix set exactly at 2 turns like the manual says, and the electric choke is also set and works fine.

650-700 idle RPM is good, with the engine "warmed up, in gear and idling in the water"

2 turns out for the idle mixture screws is not the correct final setting. This is the initial idle mixture setting, then you have to fine tune the idle mixture from there.

If the engine is idling at 600-625RPM, bump up the idle speed screw,,, bump stop screw that the throttle lever rests against at idle.