Popping Out of carb....

[Stillreelin]

Well I have a 1998 4.3 liter vortec mercruiser w/4 barral carb.Last year I replace the engine with a remanufactured one. I have the holly 4.3l 4 barrel carb on it now. What happens is the boat starts right up and runs great until it starts to go over 4000rpm. Then it will start to pop out the carb and just not run crisp. The timing is at 10 degrees BTDC . Last year I ran the Edelbrock carb . I changed jets , Metering rods and springs trying to dial it in. Some days I could get to run decent but others it would ran the same.Any suggestions would be great .

 

[Bondo]

Re: Popping Out of carb....

Ayuh,... It's goin' Lean at topend,...

It's either the carb, or elsewhere in the fuel system...

 

[Stillreelin]

Re: Popping Out of carb....

I spoke with Holly and they seem to think that the jetting is fine. That the fuel rate is not keeping up with the demand and leaning it out on top end.I will check the electric fuel pump (which is only a year or so old) pressure which should be between 3 and 7 pounds.Will triple check timing.

 

[dayonthelake]

Re: Popping Out of carb....

I have the same sort of problem.. I will be posting a new entry. Is there a difference in the requirement for the different carbs in regards to the fuel pump? If two fuel pumps have the same PSI but one has the GPH of 40 and the other GPH of 80 will that solve your problem with volume of gas at the same PSI? Does the Holley require more fuel that your old setup.

 

[sschefer]

Re: Popping Out of carb....

Have the valves ever been adjusted

 

[Stillreelin]

Re: Popping Out of carb....

Checked pressure. It goes between 6-7 psi which is good.There's is no valve lash adjustment motor.Holly guy suggested that it might be electric.The only thing not new on that is the distributor its self. Maybe the bearings are bad... Not sure if that would have anything to do with it.

 

[Don S]

Re: Popping Out of carb....

Did you check the pressure at the problem rpm? It's probably not a fuel pump problem, the problem may be lack of fuel TO the fuel pump. That's where things tend to get plugged up.
Try these tests.
http://forums.iboats.com/showthread.php?t=283269
You really need to DO the tests, don't just look at a few parts and proclaim it's ok. Without the vacuum numbers you don't know.