Re: Sputtering Mariner watch video please
That's a typical everyday lean spit.
That motor is idling way too fast, so your syncronization might be off, huge air leak, etc.
The lean spit can come from many places, but it always boils down to not enough fuel getting into the combustion chamber. Not enough fuel into the combustion chamber can be: scuffed piston, leak at the crankcase such as an upper CS seal, flange halves as well as carb issues (ruling out cleanliness, miss adjust needles, loose mounting nut, etc)
Oh, and the 2+2 is pretty simple.
Top two carbs have an adjustable needle for idle mix, so the motor only idles off #1 and #2. 1 1/4 turn is pretty standard, maybe up to 1 1/2 if this motor has a ton of hours.
The bottom 2 have a tiny hole that feeds fuel at idle for lubrication. It's not enough to change any speed really.
The accelerator pump trips when your throtle linkage advances to an engineered point.
The carbs have no major need for an idle circuit at plane speeds, so all 4 are feeding fuel now through their main jets on plane.
You can have a multitude of issues, form simple to fatal:
1) Sync/link is off
2) Air leak from some where
3) Still a carb issue such as missing hardware, not clean, installed in wrong order.
4) Scuffed pistons or worn pistons due to high hours
Easiest way to find an air leak is spritz some carb cleaner around the outside of the engine (pull your hood) while it's running. If it perks up in a certain area, then there's your leak.
More info needed please.
What are your compression numbers, in order?
What plugs are you using, and pics of the respective plug to cylinder location, to look at a burn pattern? Here's an example from my 1800 Honda VTX
You can see a noticable burn pattern difference here.
It's the first place I start on any engine: with a spark plug inspection. Then compression, then leakdown, then spark, finally a fuel sample.
