air fuel mixture screw settings on 75 mercury 850 85 hp?

BOATER 1

Cadet
Joined
Mar 24, 2009
Messages
6
does anyone know what the air fuel mixture screws on the front of the carbs are supposed to be set at from the factory ,my motor is a 1975 mercury 850 85 hp out board . there is a adjustment screw on the front of each carb I am assuming that they are the mixture screws? The motor runs awsome but seems to want to load up wile idleing .what rpm should the motor idle at ? really need some help!!!!!!!!
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,030
Re: air fuel mixture screw settings on 75 mercury 850 85 hp?

Normally those mixture screws are set at 1-1/2 turns out from lightly seated. They they are adjusted from there. Normally you need to richen them up a bit to allow smooth acceleration. It sound slike yours are a bit too rich.

Idle speed should be anything below 900RPM in the water, as low as you can get it to run at.
 

BOATER 1

Cadet
Joined
Mar 24, 2009
Messages
6
Re: air fuel mixture screw settings on 75 mercury 850 85 hp?

mine idles at 1100 or it loads up and dies it accelerates pretty smooth it also seems to use alot of gas.so the silver sscrews on the front of the carbs should go in to lean and out to richen?thanks for the help
 
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