1993 chris craft omc king cobra misfire

[Chriscraft268]

Needing some guidance on a backfire issue. 1993 omc king cobra 7.4 liter. Sit for 5 years. Boat was winterized. 2 weeks ago we tried getting it going. Drained all fuel (7 gallons) put new fuel in, rebuilt carb holley 4150. New plugs,wires,cap and rotor. Checked compression 6 of cylinders 151lbs 2 cylinders 152lbs. Leak down test on valves test good. Problem im having is back firing through carb. Looks like 4 of plugs are firing light brown/black other 4 still white with fuel on them. Any idea on where to go from here. Considering switching the eem spitfire module out. But want to make sure thats the problem. Parts replacing can be expensive and frustrating. I am in the process of checking timing gear and seeing if its timed correctly.

 

[matt167]

How many is it missing on?

 

[Scott Danforth]

go back and re-clean the carb. you need to make sure you feed a wire or string thru every passage of the holley to ensure its clean.

backfiring thru the carb is running lean. you state that 4 plugs are white (without fuel). since the manifold is a dual plane manifold, half of your carb is not feeding fuel.

 

[Chriscraft268]

I must of wrote that wrong, all plugs have fuel on them. But i can do that to the carb, i have the front end of the motor apart, checking to see if it has jumped time. Is the timing still set the same. Bring number 1 to TDC and align the rotor pointing to number 1