Carb Adjustment

[garyreno]

I have a 1983 90 Hp Chrysler that seems to run to rich. The Manual says to back the adjustment screw off one full turn counterclockwise, then clockwise is lean and counterclockwise is rich. Both carbs are only backed off about 1/2 to 3/4 of a turn and still to rich. Is it time to rebuild the carbs or is there something else that needs to be serviced?

 

[redmule]

Re: Carb Adjustment

Gary<br />If the motor is in time, plug wires & plugs good, getting fire to the cyclinders and Fuel mix is right.<br />I think you may be adjusting the idle screws, which you turn in till they seat (lightly) and then turn out 1 turn. (Turn in restricts air, out opens it to moore air) Get the idle adjustment right.<br /> [EDIT FOR THE ABOVE SENTENCE SHOULD BE; IN RESTRICTS FUEL & OUT INCREASES FUEL ] <br /><br />If it is still runing rich after the idle adjustment then you may have a bad main jet or the float is bad or need adjustment, time to rebuild carbs I would say.

 

[eurolarva]

Re: Carb Adjustment

Are you noticing any difference in the motors perfomance when you adjust the mixture screws? I dont think the motor has an idle screw only the mixture screw. Are you running the correct plugs? If you notice little or no effect on motor performance with the mixture screws then you are going to have to clean and rebuild.

 

[redmule]

Re: Carb Adjustment

Gary check your carb against this site to id your carb and parts<br /> http://www.mercruiserparts.com/SelectModelType3.asp?class_id=2 <br />Eurolarva may be right and I may be wrong but the mixture screws are for idle adjustment only.I do not think it has a high speed mixture screws. The condition and size of the main fuel needle & seat will determine the amount of fuel available too carbs when running idle to wot . If it is bad you can have either to lean or to rich of a mixture. <br /><br />Also when, at idle or wot is it running rich? Here is another helpful link <br /> http://www.themarinedoctor.com/fuelproblems.htm

 

[garyreno]

Re: Carb Adjustment

It only runs rich at idle, at WOT it runs great, gets about 4900 rpm. The plugs are new and the correct UL18V. When I adjust the carbs I do notice a difference but where ever I adjust to, it still puts out to much white smoke at idle and runs rough, and sometime dies.

 

[eurolarva]

Re: Carb Adjustment

Chryslers are notorious for poor idleing. My 67 chrysler has drain hoses on the port side to take excess fuel from the cylinders and drain them out the motor leg. I talked to Franz at the Chrysler Crew and he said. <br /><br />"In 1967 this was the answer to excess gas puddling in the cylinders at idle. This buildup of gas would not allow the motor to idle for very long without getting rid of it somewhere and enviornmental issues were not much on the minds of the engineers. Later this gas was recycled back into the motor behind the carbs but no motor idles better than the old ones. To the best of my understanding, the valve would let excess gas pass into the motor leg on the compression stroke but would not let air or water be pulled back on the intake stroke. These valves have not been available for some time but I will try to locate one that will work properly".<br /><br />I have been experiencing gas going into the water and am trying to eliminate the problem. My check valve is not working correctly and that is what he is refering to in the email. <br /><br />You may be stuck with the poor idle. I would not set carbs to run leaner then they already are. The Marine Doctor also mentioned that the timing should be advanced to 30 degrees instead of 32 to allow for the use of unleaded gas. Hope some of this is of help to you.