merc 170 carb trouble

[lewski]

hi,my 170hp merc is rough on the start until completely warmed up,carb backfires once and awhile.Noticed it has one adjustment screw on the side of carb,and was wondering how to set it.tried just about everything else,complete tuneup but still runs rough and blows alot of black smoke but once warm there is no visible smoke. can anyone help,thanks

 

[dubs283]

Re: merc 170 carb trouble

is the choke operarting correctly??

is the carb leaking down upon shut down??

the idle mixture screw is located at the base of the carb, turn it in 'til the enigne stumbles, then out 'til the engine stumbles, then back in half the amount of turns (between stumbles)

the idle speed screw is at the back of the carb, used to set, well...idle speed

 

[Bamaman1]

Re: merc 170 carb trouble

+1 on #2. The old 470 Rochester carb. is about as simple as they come. I had to come up with another carb for some of its parts--off a 307 Chevy engine dating back to 1967.

 

[lewski]

Re: merc 170 carb trouble

thanks, ill give it a try