1989 Mercury 75 3 cylinder bogging and wont plane out

[procraftdawg205]

Ive replaced all fuel lines, check compression, checked firing on all 3 cylinders, replaced stator and trigger. The motor will crank and run find put once you throttle it up it begins to backfire like it is loading up in one cylinder. I also checked the fuel pump and filter and all look fine. Any idea what the problem is?

 

[Silvertip]

Looking at the fuel pump is not a valid check. You need to check fuel pump pressure and volume. Spark, fuel, and air and all must happen at the proper time. Only you can figure out which one is missing. You didn't give compression numbers, you said you have spark but is it good spark. Did this motor ever run correctly for you or did you just acquire it. Running rich (loading up as you say) does not cause backfire but a lean condition (lack of fuel) or incorrect timing and carb synchronization can.

 

[ondarvr]

Cleaning the carbs is a very good place to start.

 

[procraftdawg205]

I acquired this from a guy who "fixed" it but never took it to the lake to run it. I plan to remove carbs one day this week and check em. The spark was fine so I think it's a fuel issue