Adjust Air/Fuel Ratio

[Asterope8]

I have a 1982 Evinrude 90 hp outboard. I need to know how to adjust the air to fuel ratio. I also need to know what the psi is for the compression. Thank you!

 

[racerone]

Re: Adjust Air/Fuel Ratio

It may have fixed idle jets.------------Most important thing is to have even compression on all 4 cylinders.-----------Are there problems with the motor ??

 

[OptsyEagle]

Re: Adjust Air/Fuel Ratio

http://forums.iboats.com/engine-fre...sorted-carb-variations-joe-reeves-167352.html

 

[racerone]

Re: Adjust Air/Fuel Ratio

Those are very detailed / good instructions.--------But the motor in question does not have any mixture adjustment needles !!--------The poster would be better off to list the problems with the motor.---Or perhaps the elevation that it is being run at.---------For some strange reason many folks think that the carburetor is the first thing to be looked at.

 

[Asterope8]

Re: Adjust Air/Fuel Ratio

It seems that the bottom carb is not getting fuel. Does anyone know how to help?

 

[racerone]

Re: Adjust Air/Fuel Ratio

Squeeze the primer bulb.----Then remove the lower drain screw on the side of the carburetor.----Does fuel come out ?---------Squeeze the primer bulb again and see what happens.------What is the history on thiis motor? ---When did it last run properly ?--Did it sit for a long time with fuel in the carburetors ?----Information needs to be posted !

 

[Joe Reeves]

Re: Adjust Air/Fuel Ratio

It seems that the bottom carb is not getting fuel. Does anyone know how to help?

After pumping the fuel primer bulb up hard, remove the drain screws from that carburetor to see if fuel is or is not entering the carburetor float chamber.

If fuel is present, your present question has been answered. Now.... what exactly is the engine doing or not doing?

The basic trouble shooting procedure is to check the compression first... what are the psi reading of all the individual cylinders?

Secondly, with all the spark plugs still removed, check for proper spark which should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Does it?.... Note that the 7/16" gap is important!

 

[Asterope8]

Re: Adjust Air/Fuel Ratio

I bought the boat a month ago, it ran two weeks ago. The problem was that I ran the tank inside the boat not knowing that there wasn't a fuel filter in line and everything got clogged. The guy that sold it to me originally ran a 6 gal tank and never told me that there was no fuel filter and ran it that way because it was "cheaper on gas." I am a first time boat buyer and didn't know all of this. I cleaned the tank with denatured alcohol and have yet to use it since. I ran a water separator and put an inline fuel filter in the motor.
The motor is not firing so I cannot get compression readings.

 

[Asterope8]

Re: Adjust Air/Fuel Ratio

I took the silencer lid off so that is how I know that it's not getting fuel. The top one is but the bottom one isn't.

 

[Asterope8]

Re: Adjust Air/Fuel Ratio

Ok - I got it to start but it will only stay running if I hold in the choke.

 

[racerone]

Re: Adjust Air/Fuel Ratio

The compression test has nothing to do with the firing.-----Remove the sparkplugs and use a compression tester , the first thing to do on a problem motor..----------If you answer specific question posted we can help you.------When you remove the float bowl drain screw one side or the other, is there fuel there ???-----There usually is a screen on the fuel pump cover to keep out large bits of dirt.

 

[Asterope8]

Re: Adjust Air/Fuel Ratio

Yes they is fuel coming out of the brass couplings but still no fuel coming out of the bottom carb when you look at it taking the black silencer cover off. I got the .030 spark plug gap specs from the internet but I am not quite sure that is right. That's what I ran the boat on before it worked fine. I think the problem might be a connection in the wires from the key switch because when I hold down the key and turn it, it will stay on for like 10 sec but that is it.

 

[racerone]

Re: Adjust Air/Fuel Ratio

One more try here.-------When you remove the drain screw from the side of the carburetor bowl, does fuel pour out ?-------We are not asking about the sparkplug gap.--We are asking you to test and see if your ignition system will produce enuff voltage to jump a gap of 7/16"or more on each plug wire !

 

[Asterope8]

Re: Adjust Air/Fuel Ratio

Yes, fuel pours out. I don' know how to check for a 7/16" gap, can you tell me? I have a voltage reader.

 

[Asterope8]

Re: Adjust Air/Fuel Ratio

When you are looking from the back side, the right pair of spark plugs are not firing.