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Dirty spark plugs 1976 75 hp

12simo12

New member
Hi all

I have a 1976 75 hp Chrysler, my spark plugs are getting very dirty quite quickly and will only run for a day or two then will conk out. but with new sparkys it will run fine again.

Any suggestions as to why?
 
Re: Dirty spark plugs

Possibly too much oil in the gas.That motor needs to run 50-1. 1 pint oil to 6 gal.
That OK then reset the air screw.Top front of carbs.Screw in till it just bottoms out.Then out 1 turn.
You need to have it in the water,in gear and the motor warm to do final adjustment.
Turn in the screws(one at a time)till the motor just starts to miss/cough or stutter. Then out 1/2 turn.Do this on all three.Give it a few seconds to catch up between adjustments.Rev it up between carbs.
How old is the diaphram?Replace it if it's older than a year.J
 
Re: Dirty spark plugs

Thanks for the info.
The ratio i use is 1:50, and i will try the air screws on the carby.
Sorry about the lack of knowledge but what is the diaphragm and where is it located.
 
Re: Dirty spark plugs

Is the motor warming up ( thermostat in place if equipped with one )---------------------Fuel pump diaphragm should be checked as well.---------------------Will spark jump a gap of 5/16" or better.
 
Diaphragm is in the fuel pump.Thermostat is located on the top of the head above the plugs.
Get a manual and fill out the profile,you might be close to someone who can help.J
 
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