Idle speed

[8x56mn]

I have a 1981 Sting Ray MC 140 hp 3.0. It has a MC carb with 2 adjustment screws for the idle adjustment (correct). It starts up great, and I have to advance the throttle a little when cold to keep it running and then when it warms up a bit the idle increases and I have to back it down. The problem I'm having is after running a while if I back the throttle all the way back it will almost stall running around 600. I belioeve that the screws are for the idle adjustment correct, what speed is recomended for idleing and what is the best way to adjust these screws.

 

[Don S]

Re: Idle speed

Idle speed should be 650 to 700 rpm (in fwd gear).
The idle SPEED adjustment is on the linkage the cable attaches to.
The 2 screws I think you are refering to are the idle mixture adjustment for gas/fuel mixture.

 

[8x56mn]

Re: Idle speed

Idle speed should be 650 to 700 rpm (in fwd gear).
The idle SPEED adjustment is on the linkage the cable attaches to.
The 2 screws I think you are refering to are the idle mixture adjustment for gas/fuel mixture.

Thanks Don for the quick reply, I'm worried that if I raise the idle that it will cause me prolems when I'm docking. Do you think that it would be OK to just increrase it a little to prevent staling. It has stalled only once, but it also starts hard when hot, what I mean is I have to push the throttle forward a little to make it fire up and keep running, this can't be normal, or is it.

 

[180shabah]

Re: Idle speed

No, it is not normal. When properly adjusted/tuned a carbed engine should start easy, idle smoothly, and accelerate strong. You are worried that increasing your idle speed by 50-100rpm will make docking more difficult. I think you will find that there is very little extra speed created by this, and it will be much less of a problem than a boat that stalls at the wrong time. You need to get the idle speed set properly, then you can adjust your idle mixture.