4.3 L Merc Running Rough

[fireman4203]

I have a 1998 Mercuriser 4.3L that is running rough. I have replaced the cap, rotar, plugs, wires and fuel filter. It idles a little rough and when I give it gas it hesitates and and backfires. Any suggestions?

 

[danond]

Re: 4.3 L Merc Running Rough

Carb is messed up. Does it need a rebuild? Did you leave untreated gas in the engine/carb over winter?

Pour some seafoam in the tank. See if that helps (probably won't). My guess - carb needs a rebuild kit.

 

[fireman4203]

Re: 4.3 L Merc Running Rough

Do you think that it could be timing or just go with the seafoam / carb rebuild?

 

[Bondo]

Re: 4.3 L Merc Running Rough

Do you think that it could be timing or just go with the seafoam / carb rebuild?

Ayuh,... Didn't you Time it when you did the Tune Up,..?? Why not, that's part of the process....

I'd bet the Real Issue is the Carb though...

 

[fireman4203]

Re: 4.3 L Merc Running Rough

OK.... Went to check the timing but cannot find the timing marks. Sorry for being a complete knucklehead but can someone help me out? It a merc 4.3L with thunderbolt ignition. I am aware of the process of putting into base timing mode but cannot find the marks...

 

[180shabah]

Re: 4.3 L Merc Running Rough

Finish the tune up, but before you drop money on the carb, eliminate the fuel itself as a possible cause.

Run from an outboard tank with fresh gas, through the water seperator.

 

[cooter2506]

Re: 4.3 L Merc Running Rough

Backfiring thru carb is a lean fuel condition. Your lacking fuel from somewhere.