1994 mercury force 70hp

[shoeman1957]

I have completely rebuilt this engine, bored it .to 020 over, had a outboard mechanic set the timing but it coughs real bad at idle and warm up, is this a carb issue, idle /air mixture issue or what, I have gone through the carb twice

 

[jerryjerry05]

You do the starting fluid test??
Start motor, spray SF around the intake side of the motor,that includes the base of the carb and the 3 port covers, under the base of the intake, basically that whole side of the motor.
If spraying makes the motor cough,stutter, backfire??? then it's sucking air from somewhere??
My guess is that the port covers are leaking, maybe the intake bolts loose??
Post the results.
Try pinching off the tiny hose from the primer to the carb?
Sometimes the diaphragm in the primer goes bad and you get those results.

 

[racerone]

Open low speed mixture screw (s ) about 1/8th turn at a time and test run.

 

[Drivewayboater2]

Both recommendations from above are spot on. Both of those guys know their stuff. They helped me immensely.
be sure that you be patient when adjusting idle screw… give the engine time to settle ( 20/30 seconds) and adjust when messing with idle screw. tell me how I know.

 

[jerryjerry05]

There's "air screws" and there's an "idle screw".
The air screw(ususlly on the top of the carb) is adjusted to make the motor run smooth.. While it's doing that it also mixes the air fuel ratio.
The idle screw assembly is usually on the towershaft.
U-tube Videos look for them, They can be realllllllly helpful when attempting a new job.