backfires when goosed

[ljgill]

I have a 1980 Merc 470. It starts fine runs fine idles fine and will go up to 4000 rpm with no problem except when you want to take off fast like say water skiing. If I slam the throttle on it backfires and quits but if I apply the throttle slow and steady its ok. Is this acc pump do you think or ignition advance or what else. Thanks for any ideas.
Laurence

 

[bspeth]

Re: backfires when goosed

Did you check the timimg?

 

[Maclin]

Re: backfires when goosed

Sounds like accel pump shot but the igntion tuning and timing can be a factor.

 

[JASinIL2006]

Re: backfires when goosed

I had a similar problem and the shop rebuilt my carb - said it was a bad accel pump. Works fine now.

 

[alldodge]

Re: backfires when goosed

+ 1 on timing issue. Has anyone messed with the engine, like out an automotive distributor in place of a marine?

 

[180shabah]

Re: backfires when goosed

Accelerator pump....
Probably best to do complete carb overhaul...

 

[Fastatv]

Re: backfires when goosed

Could very well be the accelerator pump...sounds like it, and the power system could also be a contributor to the "lean" condition. Don't know which carb you have, but, some pumps are adjustable....to a degree. Is this a new problem? A problem that has gotten worse over time? Whats happens when you "slam" it at 2500 or 3000 rpms....? Same thing?

 

[ljgill]

Re: backfires when goosed

thanks all you guys for confirmation of my thoughts. I guess I will get busy this winter and check out the timing and have the carb rebuilt professionally.
cheers Laurence

 

[thumpar]

Re: backfires when goosed

These carbs are easy to work on. You could rebuild it yourself.