3.0 backfires through carb

[hardlearner]

I have a 3.0 litre mercruiser. It is a 96 model and has the merc carb. Just got the boat and working through some small issues. Would not idle. Man I got it from said he rebuilt carb. Took it apart and adjusted float level. Boat idles smooth. Accelerates good but when just above 3,000 rpm it wants to backfire through carb. Any ideas?

 

[NHGuy]

Re: 3.0 backfires through carb

Check timing, wires, plugs, cap, rotor, fuel delivery system.
You'll get more input from others to confirm but I believe you must make a wiring connection during timing check to get the distributor into base timing mode.
The rest of the ignition is like any other engine. Wires on my 89 looked good to my eyes but made a major improvement when I put new ones on.
Fuel delivery system includes a vent, an anti siphon valve, the fuel line, a likely fuel/water separator filter, and the little screen before the fuel enters the carburetor. I'd go through those just because I'd want to know they are right.

 

[hardlearner]

Re: 3.0 backfires through carb

good advice. was surprised I do not have a fuel/water seperator. Will check ignition and install water seperator.

 

[Monte1961]

Re: 3.0 backfires through carb

Most of the time I have found two things that cause backfiring up through the carburetor. 1. Of course is timing. 2. A lean condition. With what you are describing on what engine does, I suspect carb issues. Post back and let us know what you find!

 

[saaabe]

Re: 3.0 backfires through carb

it sound like your engine is out off timing. check in youtube for 3.0l mercruiser timing it will save you a lot of time!!!