backfire while opening throttle

[freddyray21]

I got a backfire through the carb when opening up the throttle from idle to wot. It backfires then takes off and runs. I am thinking the advance is not working properly. I have 1972 120hp Mercruiser running points (new with dwell at a steady 30 degrees), new cap, rotor, plugs and wires. Seems to overcome the backfire and run, but I could do without the hesitation when pulling a skier up. Fred

 

[lilmandavis]

Re: backfire while opening throttle

accelerator pump might not be workin right. go electronic

 

[bamadave]

Re: backfire while opening throttle

lilman, what the heck is an electronic accelerator pump?

 

[lilmandavis]

Re: backfire while opening throttle

dont you know?!? electronic pickup in the dist. oops!

 

[freddyray21]

Re: backfire while opening throttle

accelerator pump is working fine. When I pump it I get a good stream of gas. Could it be I have it too lean on idle. I had to lean it out a lot to get it to idle down. It runs smooth on idle, but each screw is only open about 1.25 turns.

 

[freddyray21]

Re: backfire while opening throttle

accelerator pump is working fine. When I pump it I get a good stream of gas. Could it be I have it too lean on idle. I had to lean it out a lot to get it to idle down. It runs smooth on idle, but each screw is only open about 1.25 turns.

 

[lilmandavis]

Re: backfire while opening throttle

yes its possible. when setting the carbs i set the idle with the set screw. after i get a proper rpm like that, i turn the jets till the motor starts to idle down. after the engine has a slight change i turn the screw out 1/8-1/4 turn. make sure both jets are in sync, you surely dont want to run lean